U.S. patent application number 09/906225 was filed with the patent office on 2002-02-07 for amperometric sensor probe for an automatic halogen control system.
Invention is credited to Calic, Caba, Silveri, Michael A..
Application Number | 20020014410 09/906225 |
Document ID | / |
Family ID | 26745017 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020014410 |
Kind Code |
A1 |
Silveri, Michael A. ; et
al. |
February 7, 2002 |
Amperometric sensor probe for an automatic halogen control
system
Abstract
An amperometric bromine control system accurately maintains a
desired concentration of bromine within a home spa or in other
water features. The control system employs amperometric sensing to
measure the bromine concentration in the spa water and uses this
measurement to control the electrochemical production of bromine
through the oxidation of aqueous bromide. The level of bromide in
the spa water desirably is greater than 50 ppm in order to obtain a
linear relationship between the current level sensed through the
amperometric measurement and the concentration level of bromine in
the water. In this manner, the control system can accurately
measure the bromine concentration in the spa water and precisely
maintain the bromine concentration within a desired range between
about 2 ppm and 6 ppm.
Inventors: |
Silveri, Michael A.;
(Incline Village, NV) ; Calic, Caba; (Reno,
NV) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
620 NEWPORT CENTER DRIVE
SIXTEENTH FLOOR
NEWPORT BEACH
CA
92660
US
|
Family ID: |
26745017 |
Appl. No.: |
09/906225 |
Filed: |
July 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09906225 |
Jul 16, 2001 |
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09187623 |
Nov 6, 1998 |
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6270680 |
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60064899 |
Nov 7, 1997 |
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60075276 |
Feb 19, 1998 |
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Current U.S.
Class: |
204/412 |
Current CPC
Class: |
C02F 1/72 20130101; C02F
2001/46123 20130101; C02F 2303/04 20130101; C02F 2201/4611
20130101; C02F 2001/46119 20130101; C02F 2209/06 20130101; G01N
27/44 20130101; Y02W 10/37 20150501; C02F 1/42 20130101; C02F
2001/46128 20130101; C02F 2201/46125 20130101; C02F 2201/4612
20130101; C02F 1/4674 20130101; C02F 2209/006 20130101; C02F
2103/023 20130101; G01N 27/4045 20130101; C02F 2201/4617 20130101;
C02F 1/008 20130101; C02F 1/766 20130101; C02F 2103/42 20130101;
C02F 1/46104 20130101 |
Class at
Publication: |
204/412 |
International
Class: |
G01N 027/26 |
Claims
What is claimed is:
1. An amperometric sensor probe comprising: a housing; a working
electrode and a counter electrode, each electrode having a portion
which is exposed relative to the housing at a working end; a
reference electrode immersed in an electrolyte and positioned
within the housing; a junction arranged between the electrolyte and
an exterior of the working end to allow ionic communication between
the working end exterior and the electrolyte; a memory device
positioned within the housing; and a data port, said data port
being connected to said memory device and to said electrodes.
2. The sensor probe of claim 1, wherein the memory is an
electrically erasable programmable ROM.
3. The sensor probe of claim 2, wherein the memory device stores
data that is specific for the sensor probe.
4. The sensor probe of claim 3, wherein the data specific for the
sensor probe represents a current response being caused by this
sensor probe and being indicative of a concentration of a chemical
species in water, said current response defining a preset parameter
when connected to a control system.
5. The sensor probe of claim 1, wherein said junction comprises a
porous membrane occupying an opening in the housing on the working
end.
6. The sensor probe of claim 1, wherein the exposed portions of the
working and counter electrodes lie adjacent to each other.
7. The sensor probe of claim 1, wherein the working and counter
electrodes are comprised of a carbon-based material.
8. A method for a determining measurement characteristic of a
sensor probe, comprising the steps of: providing a sensor probe
with a memory device; placing the sensor probe into a known
environment; determining a measurement characteristic of the sensor
probe when placed into said known environment; and storing in said
memory device the measurement characteristic of the sensor
probe.
9. The method of claim 8, further comprising the step of providing
an aqueous solution as the known environment for the sensor probe,
said aqueous solution having a known concentration of a chemical
species.
10. The method of claim 9, further comprising the step of
determining a current response of the sensor probe when brought
into contact with the aqueous solution.
11. The method of claim 10, wherein storing said measurement
characteristic includes storing the current response associated
with the known concentration of the chemical species in the aqueous
solution.
12. The method of claim 11, further comprising the steps of
calculating additional current responses associated with other
corresponding concentrations of the chemical species based on the
aqueous solution of known concentration, and storing in the memory
device each calculated current response for a corresponding
concentration of the chemical species in an aqueous solution.
13. The method of claim 12, wherein calculating said additional
current responses involves extrapolating said calculated current
responses using at least said determined current responses.
14. The method of claim 12, wherein calculating said additional
current responses involves interpolating said calculated current
responses using at least said determined current responses.
15. The method of claim 11, further comprising the steps of:
providing a second aqueous solution of a known second concentration
of a chemical species; bringing the sensor probe into contact with
the second aqueous solution; determining a second current response
of the sensor probe at said known second concentration; storing in
the memory device the second current response associated with the
second concentration of the chemical species in the second aqueous
solution.
16. The method of claim 15, further comprising the steps of
calculating additional current responses associated with other
corresponding concentrations of the chemical species based on the
aqueous solution, and storing in the memory device each calculated
current response for a corresponding concentration of the chemical
species in an aqueous solution.
17. The method of claim 16, wherein calculating said additional
current responses involves extrapolating said calculated current
responses using at least said both determined current
responses.
18. The method of claim 16, wherein calculating said additional
current responses involves interpolating said calculated current
responses using at least said both determined current
responses.
19. In combination, a water feature containing water, and an
amperometric sensor probe in contact with the water of the water
feature, the sensor probe comprising: a housing; a working
electrode and a counter electrode, each electrode having a portion
which is exposed relative to the housing at a working end; a
reference electrode immersed in an electrolyte and positioned
within the housing; and a junction arranged between the electrolyte
and exteriors of the working ends to allow ionic communication
between the working end exteriors and the electrolyte.
20. The combination of claim 19, wherein said junction comprises a
porous membrane occupying an opening in the housing on the working
end.
21. The combination of claim 19, wherein the exposed portions of
the working and counter electrodes lie adjacent to each other.
22. The combination of claim 19, wherein the working and counter
electrodes are comprised of a carbon-based material.
23. The combination of claim 19, wherein the reference electrode
comprises a silver/silver chloride wire.
24. The combination of claim 19, additionally comprising an
electrical connector located on a side of the housing opposite of
the working end.
25. The combination of claim 24, wherein said housing has an
elongated, tubular body extending between the working end and the
end on which the electrical connector is disposed.
26. The combination of claim 24, additionally comprising shielded
conductors which couple said working and counter electrodes, which
are located at the working end of the housing, to the electrical
connector, which is on the opposite side of the housing.
27. The combination of claim 26, additionally comprising a printed
circuit board mounted within the housing, said electrical connector
being attached to a side of the board facing away from the working
end, and said shielded conductors connected to the board on an
opposite side, said printed circuit board connecting said shielded
conductors to the electrical connector.
28. The combination of claim 27, wherein said housing includes a
cap attached to an end of the tubular body near the electrical
connector, and said printed circuit board being attached to said
cap.
29. The combination of claim 27, wherein said reference electrode
is connected to the printed circuit board which interconnects said
electrical connector and said reference electrode.
30. The combination of claim 19, additionally comprising a pH
electrode having a portion which is exposed relative to the housing
at the working end.
31. The combination of claim 19, wherein the housing comprises an
end plug having at least three openings, a first of the openings
receiving the working electrode, a second of the openings receiving
the counter electrode, and the third of the openings receiving the
junction, and the electrodes being potted within the end plug.
32. The combination of claim 31, wherein the end plug lies at
proximate to the working end of the housing so as to position the
working and counter electrodes at the working end, and the housing
includes an external thread extending about the end plug.
33. A method for automatically maintaining the concentration of a
sanitizing agent in a water feature within a preset range using an
automatic sanitizing system, comprising the steps: providing an
aqueous solution with a sanitizing agent in the water feature;
providing an amperometric sensor probe including at least a
reference electrode and a working electrode; placing at least a
portion of the working electrode in contact with the aqueous
solution; maintaining a generally constant preset voltage between
the electrodes; measuring a current through the working electrode
which is indicative of the concentration of the sanitizing agent
within the aqueous solution; and using the measured current to
maintain the concentration of the sanitizing agent in the aqueous
solution within the preset range.
34. The method of claim 33, additionally comprising producing a
flow of aqueous solution over said working electrode before
measuring the current.
35. The method of claim 33, additionally comprising preforming
diagnostic checks of at least some components of the automatic
sanitizing system when producing the aqueous flow over said working
electrode before taking the current measurement.
36. The method of claim 33, additionally comprising
electrochemically producing the sanitizing agent when the measured
current is below a preset range.
37. The method of claim 36, wherein electrochemically producing the
sanitizing agent comprises providing an electrolyte within the
aqueous solution and circulating a portion of the aqueous solution
through an electrolytic cell.
38. The method of claim 37, additionally comprising energizing the
electrolytic cell when the measured current is below the preset
range.
39. The method of claim 38, additionally comprising clocking a
cumulative operating time of the electrolytic cell, determine when
the cumulative operating time exceeds a preset duration, and
cleaning the electrolytic cell when the cumulative operating time
exceeds the preset duration.
40. The method of claim 37, additionally comprising operating the
electrolytic cell in a deenergized mode when the measured current
is above the preset range.
41. The method of claim 37, additionally comprising: controlling
the operation of the electrolytic cell over a series of consecutive
duty cycles; determining whether the electrolytic cell was
energized during at least a portion of the immediately preceding
duty cycle; and energizing the electrolytic cell when the measured
current is within the present range and the electrolytic cell was
energized during at least a portion of the immediately preceding
duty cycle.
42. The method of claim 37, additionally comprising: controlling
the operation of the electrolytic cell over a series of consecutive
duty cycles; determining whether the electrolytic cell was
energized during at least a portion of the immediately preceding
duty cycle; and operating the electrolytic cell in a deenergized
mode when the measured current is within the present range and the
electrolytic cell was not energized during any portion of the
immediately preceding duty cycle.
43. The method of claim 33, wherein maintaining the voltage between
the reference electrode and the working electrode involves
providing a counter electrode coupled to the reference electrode
such that the reference electrode provides a feedback signal to the
counter electrode.
44. The method of claim 43, additionally comprising applying a
sequence of three different references voltages between said
working electrode and said counter electrode during a cleaning
cycle.
45. The method of claim 44, wherein at least one negative potential
and at least one positive potential are applied during the cleaning
cycle.
46. The method of claim 44, wherein said cleaning cycle comprises a
cleaning step of applying a reference voltage of +1 volts for one
minute between the working and counter electrodes, applying a
reference voltage of -80 millivolts for one minute between the
working and counter electrodes, and applying a reference voltage of
+300 millivolts between the working and counter electrodes.
47. The method of claim 46, wherein the cleaning step is performed
in the following sequence: applying a positive potential between
the working and counter electrodes; applying a negative potential
between the working and counter electrodes; and applying a positive
potential between the working and counter electrodes.
48. The method of claim 46, wherein the cleaning step is performed
at least five times during the cleaning cycle.
49. The method of claim 44, additionally comprising applying a
fourth reference voltage between the counter electrode and the
working electrode with the fourth reference electrode corresponding
to a reduction potential of a chemical species other than the
sanitizing agent being measured.
50. The method of claim 43, wherein maintaining the voltage between
the reference electrode and the working electrode additionally
involves providing a potentiostat coupled to the working, counter
and reference electrodes, said potentiostat including a plurality
of operational amplifiers.
51. The method of claim 50, additionally comprising applying
asymmetric power to at least one of the operational amplifiers.
52. The method of claim 51, wherein a positive voltage of about +5
volts and a negative voltage in the range of about -4.2 volts to
about -4.5 volts is applied to the at least one operational
amplifier.
53. A method of cleaning a first electrode of a probe, with the
probe including at least the first electrode and a second
electrode, comprising applying a sequence of three different
references voltages between said first and second electrodes.
54. The method of claim 53, wherein at least one negative potential
and at least one positive potential are applied between the
electrodes as two of the three reference voltages.
55. The method of claim 53, wherein applying the sequence of three
different reference voltages involves applying a reference voltage
of +1 volts for one minute between the electrodes, applying a
reference voltage of -80 millivolts for one minute between the
electrodes, and applying a reference voltage of +300 millivolts
between the electrodes.
56. The method of claim 55, wherein the reference voltages are
applied in the following sequence: applying a positive potential
between the electrodes; applying a negative potential between the
electrodes; and applying a positive potential between the
electrodes.
57. The method of claim 56, wherein the sequence is performed at
least five times.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a water purification
system, and more particularly to an amperometric sensor prove for
an automatic sanitizing system.
[0003] 2. Description of Related Art
[0004] Portable self-contained spas have become popular in recent
years. Such spas are easy installed and powered by existing
electrical lines or dedicated electrical hookups.
[0005] Once installed, the homeowner must sanitize the spa to
prevent the proliferation of disease-causing micro-organisms.
Typical spa maintenance requires adding granular sodium
dichloro-isocyanurate as a sanitizing agent to control such
bacteria growth. Bromine alternatively can be added as a sanitizing
agent. Bromine preferably is used as the sanitizing agent in the
spa because it remains in liquid form at 100.degree. F., unlike
chlorine.
[0006] Many spa owners today, however, do not properly maintain
their spas. Some owners do not adequately sanitize their spas
despite the danger of unhealthy bacteria growth. Other owners
over-sanitize their spas which can damage spa equipment, including
the heater and the spa shell.
[0007] In an effort to ease spa maintenance so as to avoid both
under- and over-sanitizing, some prior systems have automated at
least part of the maintenance. For example, an automatic demand
chlorination system is disclosed in U.S. Pat. No. 4,657,670 for use
with a recirculation unit for a swimming pool. The automatic demand
chlorination system has a dry chlorinator which feeds chlorine into
the water if a chlorine need is detected by a sensing unit. An
oxidation-reduction type sensor is used in the automated system for
this purpose. Although oxidation-reduction type sensors have been
used to measure the concentration of halogens used as sanitizing
agents in water features there are some limitations, e.g., a
nonlinear response to variations of halogen concentration or a
required calibration to changing starting points.
SUMMARY OF THE INVENTION
[0008] In view of the deficiencies associated with prior solutions
to maintain a desired concentration of a sanitizing agent and
thereby to maintain a certain hygienic condition in spa water,
there exists a need to improve accuracy, reliability and
practicability of halogen measurements in a water feature, e.g., a
spa, pool, fountain, cooling tower and the like.
[0009] An aspect of the present invention involves a combination of
a water feature containing water, and an amperometric sensor probe
in contact with the water for sensing the sanitizing agent in the
water feature. The amperometric sensor probe comprises a housing, a
working electrode and a counter electrode. Each electrode has a
portion which is exposed relative to the housing at a working end.
The amperometric sensor probe further comprises a reference
electrode immersed in an electrolyte and positioned within the
housing. A junction is arranged between the electrolyte and an
exterior of the working end to allow ionic communication between
the working end exterior and the electrolyte. In an embodiment of
the present invention, the exposed portions of the working and
counter electrodes lie adjacent to each other and comprise
carbon-like material.
[0010] A further aspect of the present invention involves an
amperometric sensor probe. The probe comprises a housing and three
electrodes: a working electrode, a counter electrode and a
reference electrode. The working electrode and the counter
electrode each have a portion which is exposed relative to the
housing at a working end. The reference electrode is immersed in an
electrolyte and is positioned within the housing. A junction, which
is arranged between the electrolyte and the exterior of the working
ends, allows ionic communication between the working ends exterior
and the electrolyte. The probe further comprises a memory device
that stores data specific for the probe. The memory device is
connected to a data port that is also connected to three
electrodes.
[0011] A still further aspect of the present invention involves a
method of cleaning a first electrode of a probe, with the probe
including at least the first electrode and a second electrode. The
method comprising applying a sequence of three different references
voltages between said first and second electrodes.
[0012] An additional aspect of the present invention involves a
method for automatically maintaining the concentration of a
sanitizing agent in a water feature within a desired range using an
automatic sanitizing system. The method comprising the steps of
providing an aqueous solution with a sanitizing agent in the water
feature; providing an amperometric sensor probe including at least
a reference electrode and a working electrode; placing at least a
portion of the working electrode in contact with the aqueous
solution; maintaining a generally constant voltage between the
electrodes; measuring a current through the working electrode which
is indicative of the concentration of the sanitizing agent within
the aqueous solution; and using the measured current to maintain
the concentration of the sanitizing agent in the aqueous solution
within the preset range.
[0013] An additional aspect of the present invention involves a
method for determining a measurement characteristic of a sensor
probe. The method comprises the acts of providing a sensor probe
with a memory device, placing the sensor probe into a known
environment, determining a measurement characteristic of the sensor
probe when placed into said known environment, and storing in said
memory device the measurement characteristic of the sensor
probe.
[0014] A still further aspect of the present invention a
combination of a water feature filled with water containing a
sanitizing agent and an automatic sanitizing system is provided.
The automatic sanitizing system comprises a sanitizing agent
generator communicating with the water feature, and an amperometric
sensor that includes a probe positioned in contact with water. The
sensor generates an output signal indicative of the concentration
of sanitizing agent in the water. The automatic sanitizing system
further comprises a control system that receives the signal from
the sensor and operates the generator at least between an active
state and an inactive state depending on the concentration of the
sanitizing agent in the water. In this manner, the concentration of
the sanitizing agent in the water is automatically maintained
within a preset range.
[0015] A further aspect of the present invention involves an
automatic sanitizing system. The automatic sanitizing system
comprises an electrolytic cell for emersion in water and an
amperometric sensor probe positionable in contact with the water.
The sensor probe generates an output signal indicative of a
concentration of a chemical species in the water. The automatic
sanitizing system further comprises a control system connected to
the sensor probe to receive the output signal. The control system
is connected to the electrolytic cell to operate the electrolytic
cell at least between active and inactive states depending on the
concentration of the chemical species in the water.
[0016] A further aspect of the present invention involves a system
comprising a controller device, a feedback circuitry, a controlled
device and a power supply unit. Additionally, the system comprises
an isolator which electrically isolates the controller device at
least from the power supply unit and the controlled device.
[0017] Another aspect of the present invention involves an
automatic sanitizing system. The automatic sanitizing system
comprises an electrolytic cell for emersion in water and an
amperometric sensor probe positionable in contact with the water.
The sensor probe generates an output signal indicative of a
concentration of a chemical species in the water. The automatic
sanitizing system further comprises a control system connected to
the sensor probe to receive the output signal. The control system
is connected to the electrolytic cell to operate the electrolytic
cell at least between active and inactive states depending on the
concentration of the chemical species in the water. Furthermore,
the automatic sanitizing system comprises means for electrically
isolating the control system from the power supply unit.
[0018] An additional aspect of the present invention involves a
combination of a water feature filled with water containing an
electrolyte prepared by the step of adding a salt composition to
the water, and an automatic sanitizing system. The salt composition
comprises at least about 50 ppm sodium bromide and at least about
500 ppm sodium chloride. The automatic sanitizing system comprises
a sanitizing agent source communicating with the water feature, an
amperometric sensor including a probe, and a control system
receiving a sensor signal and operating the sanitizing agent source
at least between an active state and an inactive state. The
sanitizing agent source includes a sanitizing agent generator or a
dispenser containing the sanitizing agent.
[0019] A further aspect of the present invention involves an
automatic sanitizing system. The automatic sanitizing system
comprises a sanitizing agent source, an amperometric sensor
including a probe, and a control system including a
microcontroller. The amperometric sensor includes a potentiostat
for amperometric measurements which comprises a plurality of
operational amplifiers, each is provided with an asymmetrical power
supply by an operational amplifier sub-power supply.
[0020] Another aspect of the present invention involves a method
for automatically maintaining the concentration of bromine in a
water feature within a preset range. The method comprises the steps
of providing an aqueous solution with a bromide concentration of at
least about 50 ppm in the water feature. Elemental bromine is
electrochemically or chemically produced in the aqueous solution
and the concentration of elemental bromine in the aqueous solution
is measured. The measured bromine concentration is used to control
the production of bromine to maintain a concentration of elemental
bromine in the aqueous solution within the preset range. In an
embodiment of the present invention, the concentration of elemental
bromine in the aqueous solution is maintained within the range of
about 2 to about 6 parts per million (ppm). The production of
bromine desirably occurs at a rate of about 1 to 2 grams per
hour.
[0021] Water features, especially spas and pools also suffer from
high transient activity causing changing hygienic conditions. A
still further aspect of the invention is therefore, to sense water
feature usage activity and to initiate production of more
sanitizing agent when usage is detected rather than to wait until
the concentration of the sanitizing agent drops.
[0022] Further aspects, features, and advantages of the present
invention will become apparent from the detailed description of the
preferred embodiment which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above-mentioned and other features of the invention will
now be described with reference to the drawings of a preferred
embodiment of the present automatic sanitizing system. The
illustrated embodiment is intended to illustrate, but not to limit
the invention. The drawings contain the following figures:
[0024] FIG. 1A is a schematic illustration of a combination of a
water feature and an automatic sanitizing system in accordance with
a preferred embodiment of the present invention;
[0025] FIG. 1B is a schematic illustration of a combination of a
water feature and an automatic sanitizing system in accordance with
a further embodiment of the present invention;
[0026] FIG. 2 is an exploded perspective view of a halogen
generator configured in accordance with a preferred embodiment of
the present invention;
[0027] FIG. 3 is an exploded perspective view of an electrolytic
cell of the halogen generator of FIG. 2 wherein a rotating bipolar
electrode is positioned between a non-rotating anode and a
non-rotating cathode;
[0028] FIG. 3A is a top plan view of the bipolar electrode of FIG.
3;
[0029] FIG. 4 is a simplified illustration of a control unit
connected to a sensor probe;
[0030] FIG. 5, comprising FIGS. 5A an 5B, is a detailed
illustration of a control unit shown in FIG. 4;
[0031] FIG. 6 is a principle illustration of a potentiostat housed
within a control unit and connected to a sensor probe;
[0032] FIG. 7 is an illustration of a power supply unit shown in
FIG. 1;
[0033] FIG. 8A is an exploded view of a sensor probe in accordance
with a preferred embodiment of the present invention;
[0034] FIG. 8B is an exploded view of an end cap and electrodes
configured in accordance with another preferred embodiment which
can be used with the basic structure of the sensor probe
illustrated in FIG. 8A;
[0035] FIG. 9A is a cross-sectional view of an assembled rear
portion of the sensor probe shown in FIG. 8A;
[0036] FIG. 9B is a cross-sectional view of an assembled front
portion of the sensor probe shown in FIG. 8A;
[0037] FIG. 10 is a diagram illustrating electrical
interconnections between a memory device and a connector;
[0038] FIG. 11, comprising FIGS. 11A and 11B, is a flowchart
illustrating the operation of the automatic sanitizing system in
accordance with a preferred embodiment of the present
invention;
[0039] FIG. 12 is a flowchart illustrating a control cycle applied
in the automatic sanitizing system;
[0040] FIG. 13 is a flowchart illustrating a cleaning cycle applied
in the automatic sanitizing system;
[0041] FIG. 14A is a graph showing a sensor probe current response
as a function of bromine concentration;
[0042] FIG. 14B is a graph showing voltage responses of different
sensor probes as a function of bromine concentration; and
[0043] FIG. 15 is an illustration of the automatic sanitizing
system including a transformer for connection to an AC line
voltage.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0044] FIG. 1A is a schematic illustration of a water feature 7 in
combination with an automatic sanitizing system 12 which is
configured in accordance with a preferred embodiment of the present
invention. For the following description of the invention, the
water feature 7 is illustrated and described as a spa, portable or
built-in. The automatic sanitizing system 12, however, also can be
used in other types of water features, such as, for example, but
without limitation, swimming pools, water fountains, industrial
cooling towers and the like.
[0045] A spa 7 is equipped with a conventional first water
circulation line 8 comprising a pump system 8a for circulating spa
water through the line 8, a filter 8b to extract leaves, bodily
hair and/or other solid impurities from the water, and a water
heating system 8c. The spa pump system 8a can include, for example,
either a two-speed pump or the combination of a booster pump and a
main pump; the pump system 8a circulates water through the line 8
at a low flow rate when operating under cleaning and/or heating
modes, and circulates water through the line 8 at a high flow rate
when operating under a user mode. The spa 7 also has several water
jets which communicate with the circulation line 8 and can be
activated together or individually by a user. When the pump system
8a operates in the user mode, these jets output water streams under
high pressure generated by the pump system 8a.
[0046] A second water circulation line 9 is attached to and
communicates with the spa 7 through two openings 10, 11. The second
water circulation line 9 desirably works independently from the
first water circulation line 8; however, the two circulation lines
8, 9 can also be integrated. In FIG. 1, however, the two water
circulation lines 8, 9 are physically separated from and operate
independent of each other.
[0047] The second water circulation line 9 is associated with the
automatic sanitizing system 12. As indicated by arrows, spa water
desirably flows within the water circulation line 9, entering the
water circulation line 9 through the influent opening 10 and
exiting the line 9 through the effluent opening 11 thereby creating
a circulation loop.
[0048] The openings 10, 11 desirably are formed in a unitary
fitting; however, the openings 10, 11 can be separately positioned
at remote locates on the spa body relative to each other.
[0049] The sanitizing system 12 is disposed within the circulation
loop formed by the water circulation line 9, and includes a
sanitizing agent source. In the illustrated embodiment, the
sanitizing agent source is a generator 20 that produces the
sanitizing agent. The generator 20 is located within the water
circulation line 9 and when activated desirably generates a halogen
sanitizing agent or an intermediate in the reaction path leading to
the halogen sanitizing agent.
[0050] A control unit 1 operates the generator 20 in accordance
with spa water characteristics that are obtained from a sensing
system which includes an amperometric sensor, and an optional
temperature sensor 13 and a pH sensor. A probe 6 desirably
functions as a combined sensor probe for the amperometric and pH
sensors, as described below.
[0051] As illustrated in FIG. 1A, the sensor probe 6 is positioned
within the water circulation line 9 to immerse at least a portion
of the probe 6 within the water flow through the line 6. The sensor
probe 6 desirably lies downstream of the generator 20. At this
location, bacteria growth (e.g., algae growth) on the sensor probe
6 is minimized.
[0052] The temperature sensor 13 is illustrated with dashed lines
to indicate that it is optional to include such a temperature
sensor 13 in the sensing system. The temperature sensor 13 is also
positioned within the water circulation line 9 so as to provide
reliable readings of the water temperature. In the illustrated
embodiment, the temperature sensor 13 is positioned upstream of the
generator 20.
[0053] The control unit 1 is connected to the sensor probe 6, the
temperature sensor 13 and a power supply unit 2. The power supply
unit 2 desirably is connected to an external power line at a line
voltage of either 120 volts or 240 volts.
[0054] In the illustrated embodiment, the control unit 1 and the
power supply unit 2 are located near the generator 20, as well as
near the sensor probe 6 and the temperature sensor 13. However, the
control unit 1 and the power supply unit 2 can be remotely
positioned relative to each other and relative to the sensor probe
6 and the temperature sensor 13.
[0055] As schematically represented in FIG. 1A, the generator 20
includes an electrolytic cell 5 and a pump 4 for circulating water
through the water circulation line 9 and the electrolytic cell 5.
The pump 4 and cell 5 desirably are integrated into a single
housing, as described below. The pump 4 and the electrolytic cell
5, however, can be contained in different housings and located at
different locations within the circulation line 9. However, it is
understood that the electrolytic cell 5 can also be positioned
directly in the water feature 7.
[0056] FIG. 1B is a schematic illustration of another embodiment of
the present invention. This embodiment is similar to the embodiment
shown in FIG. 1A; same components therefore have been identified by
the same reference numerals. In the illustrated embodiment, the
sanitizing agent source is a dispenser 20a comprising a reservoir
20b for containing the sanitizing agent and a solenoid-controlled
valve 3. An output of the valve 3 is connected to the water
circulation line 9. Via the power supply unit 2, the control unit 1
selectively controls the flow of the sanitizing agent from the
reservoir 20b into the water. The control unit 1 operates the valve
3 at least between an active and inactive state depending on the
concentration of the sanitizing agent in the water. If the solenoid
is energized during the active state, the valve 3 is opened and a
desired amount of a sanitizing agent, for example, a solid oxidizer
comprising potassium peroxymonopersulfate or a blend of sodium
chloride and bromide, is dispensed from the sanitizing agent source
20a into the water. During the inactive state, no sanitizing agent
is dispensed into the water.
[0057] From the foregoing description, those skilled in the art
will readily appreciate that other types of sanitizing agent
sources can also be used with the present sanitizing system 12.
Accordingly, the following description of the specific components
of the sanitizing system depicted in FIG. 1A is merely exemplary of
one form the present invention can take.
[0058] Generator
[0059] With reference to FIGS. 2-3, the electrolytic cell 5
included in the generator 20 has at least one cathode and at least
one anode which form an electrode pairing which is connected to a
voltage source, for example, included in the power supply unit 2.
In another embodiment, the cell 5 may include two electrode
pairings configured in a bipolar arrangement, as described
below.
[0060] A preferred embodiment of the generator 20 is shown in FIG.
2. For the following description, this embodiment of the generator
20 is used to describe the invention. The generator 20 principally
comprises a cell assembly 22 formed by an electrolytic cell 24 and
a volute assembly 26 which houses the cell 24. A motor 28 drives an
impeller 30 of the cell assembly 21 to create a flow of water
through the cell 24, as described below.
[0061] The generator 20 also cooperates with the control unit 1
(FIG. 1). The control unit 1 controls the operation of the
electrolytic cell 24 and the motor 28. The individual components of
the generator 20 will now be described in detail with reference to
FIGS. 2 and 3.
[0062] Volute Assembly
[0063] The volute assembly 26 comprises a volute 34 and a volute
plate 36 which together define an internal cavity in which the
electrolytic cell 24 is housed. The volute 34 includes a generally
cup-shaped housing 38 with a central cavity 40 having a cylindrical
shape. The volute 34 also includes a plurality of lugs 42 which
extend outwardly from the housing 38. A bolt hole 44 passes through
each lug 42.
[0064] As understood from FIG. 2, the volute 34 includes an inlet
port 46 and an outlet port 48. The inlet port 46 is configured to
direct water flow into the central cavity 40 at the center of the
volute assembly 26. The outlet port 48 is positioned on the
peripheral edge of the housing 38, generally tangentially to the
cylindrical central cavity 40 of the housing 28. This position of
the outlet port 48 encourages water flow through the volute 34, as
known in the art.
[0065] In the illustrated embodiment, the volute water inlet 46
includes a tubular segment 50 which extends axially from the center
of the volute 34 and supports a bib 52. The bib 52 extends
generally perpendicular to tubular segment 50. A water inlet
conduit 54, which communicates with the water feature, is attached
to the inlet port bib 52 to supply water to cell assembly 22.
[0066] The bib 52 communicates with the tubular segment 50 to form
an inlet flow path though the inlet port 46. So configured, the
flow path through the inlet port 46 turns 90.degree. from the bib
52 into the tubular segment 50 to direct the flow of water into the
cylindrically shaped central cavity 40 at the center of the cavity
40 and in a direction along the axis of the cavity 40.
[0067] As seen in FIG. 2, a plug 56 seals an outer end of the
tubular segment 50. The plug 56 desirably has a tubular shape which
allows a central terminal post 58 of the electrolytic cell 24 to
extend through and out of the plug 56, as described below. The plug
56 desirably includes an O-ring (not shown) which sits against the
terminal post 58 such that the plug 56 forms a seal between the
tubular segment 50 and the cell terminal post 58 to prevent water
flow through the outer end of the tubular segment 50. The plug 56
thus seals the fluid path through the inlet port 46.
[0068] The volute plate 36 of the volute assembly 26 includes a
disc-shaped body 60 with raised central portions 62, 64 on either
side of the body 60. The inner central portion 62 on the inner side
of the volute plate 60 (i.e., the side which mates with the volute
24) desirably has a shape which is sized to snugly fit within the
central cavity 40 of the volute 24. In the illustrated embodiment,
the inner portion 62 has a cylindrical shape of a diameter which
generally matches the diameter of the inner cavity. In this manner,
the central portion 62 generally closes and seals the open end of
the volute 34 so as to form the interior cavity of the cell
assembly 22.
[0069] With reference to FIG. 2, the outer central portion 64 of
the volute plate 36 has a size and shape to generally match that of
an end of the motor 28. In the illustrated embodiment, the outer
central portion 64 has a disc-like shape of a smaller diameter than
the body 60 of the volute plate 36.
[0070] The body 60 and the outer central portion 64 of the volute
plate 36 together define at least a pair of holes which extend into
the volute plate 36 from its outer side. The holes are sized to
receive threaded inserts 66 that are used to attach the motor 28 to
the volute plate 36, as described below. The threaded inserts 66
desirably consist of stainless steel and are cemented to or
integrally molded into the volute plate 36. In the illustrated
embodiment, the holes lie on diametrically opposite sides of the
center of the volute plate 36.
[0071] The volute plate 36 also defines a central bore 70 through
its axial center with a first counterbore 72 circumscribing the
bore 70 on the inner side of the plate 36. The counterbore 72 forms
a seat for a conventional mechanical pump seal 74, as described
below. A second counterbore (not shown) extends into the outer
central portion 64 to form a relief.
[0072] The volute plate 36 also includes a circular groove 76 in
the flange 78 which circumscribes the inner central portion 62. The
groove 76 provides a seat for an O-ring (not shown). When
assembled, the volute 34 and volute plate 36 compress the O-ring
between an end of the volute 34 and the outer flange 78 to seal the
union between these components.
[0073] A plurality of bolt holes 80 extend through the volute plate
36 about the peripheral edge of the outer flange 78. The bolt holes
80 desirably align with the corresponding bolt holes 44 formed in
lugs 42 of the volute 34. A plurality of fasteners (e.g., bolts and
nuts) pass through the aligned bolt holes 44, 80 and attach the
volute plate 36 to the volute 34 when assembled.
[0074] The volute plate 36 also includes a hole 82 which extends
though the inner central portion 62 and the disc body 60 at a
location within the O-ring groove 76. The hole 82 is sized to
receive a terminal post 84 of an electrode of the electrolytic cell
24, as described below.
[0075] The volute 34 and volute plate 36 desirably are formed of a
nonconductive polymer, such as, for example
acrylonitrile-butadiene-styre- ne (ABS). These components can be
constructed in any of a wide variety of ways which will be well
known to one skilled in the art. For example, these components can
be integrally molded such as by injection molding.
[0076] Drive Motor
[0077] FIG. 2 also illustrates the electric motor 28 which rotates
the impeller 30 of the electrolytic cell assembly 22. The motor 28
may operate on either alternating or direct current (i.e., either
an AC or DC motor) and desirably produces about 8 ounce-inches of
torque or greater at a rotational speed of about 1,800-1,850 rpm.
In the illustrated embodiment, the motor 28 is a 38 volt DC, 16
Watt motor, operated at 17-18 volt DC, with a diameter of about 1.6
inches (4.064 cm). It is, of course, understood that those skilled
in the art can readily select a variety of conventional motors of
various sizes and rotational speed and torque specifications in
order to suit a specific application of the generator.
[0078] Direct current motors have the advantage of very high
starting torque and low cost. Either brush or brushless designs can
be used with the present halogen generator 20. Motor speed can be
any speed resulting in the requisite outlet water pressure. One
thousand to five thousand rpm is sufficient. Erosion of the
catalytic coating due to high velocity can be held to a minimum by
turning the impeller 30 at 1,500 to 3,000 rpm. At 1,500 rpm, the
tip speed is roughly 487 cm per second, which is not excessive for
electrode coatings. As discussed in detail below, the actual
velocity the anode experiences is substantially less than that
because the water is accelerated to a speed close to that of the
impeller 30, with only the cathode being exposed to the
high-velocity water.
[0079] The motor 28 includes a drive shaft 86 which extends into
the internal cavity of the volute assembly 22 when assembled. In
the illustrated embodiment, the drive shaft 86 comprises 316
stainless steel.
[0080] The end of the drive shaft 86 includes a shoulder 88 and a
threaded stud 90. The shoulder 88 is configured such that the
impeller 30 of the electrolytic cell assembly 22 sits on the
shoulder 88 of the drive shaft 86 when assembled. As understood
from FIG. 2, the threaded stud 90 desirably includes a pair of
opposing flats which extend axially from the shaft end toward the
motor 28. The resultant truncated circular cross-sectional shape of
the stud 90 corresponds to a similar shape of a central aperture in
the impeller 30 to key the impeller 30 to the shaft 28, as
described below.
[0081] A nonconductive cap nut 92 secures the impeller 30 to the
drive shaft 28. The cap nut 92 desirably is made of polyvinyl
chloride (PVC) or like nonconductive, corrosion-resistant material.
The nonconductive cap nut 92 insulates the shaft 28 from the upper
conductive surface of the impeller 30. In this manner, the shaft 86
is cathodically protected from corrosion as it only contacts one
side (i.e., the underside) of the impeller 30, as explained further
below.
[0082] As understood from FIG. 2, the motor 28 also includes a pair
of mounting holes which extend longitudinally through the body of
the motor 28. The mounting holes are sized to receive mounting
bolts 94 which extend through the motor body and engage the
threaded inserts 66 of the volute plate 36. In this manner, the
motor 28 is secured to the volute assembly 26.
[0083] Electrolytic Cell
[0084] The electrolytic cell 24 includes at least one cathode 96
and at least one anode 98 which form an electrode pairing. In the
illustrated embodiment, the cell 24 desirably includes two
electrode pairings configured in a bipolar arrangement. That is,
the cell 24 includes a cathode 96, an anode 98, and a bipolar
electrode 30 (which functions as the impeller) interposed between
the cathode 96 and the anode 98. The cathode 96 and the anode 98
polarize the corresponding sides of the electrode 30 such that one
side of the electrode 30 function as an anode and the other side
functions as a cathode to provide two cathode/anode pairings. As
illustrated by the other embodiments of the electrolytic cell
described below, however, any of a wide variety of cell
configurations, which will be readily apparent to those skilled in
the art, can be used with the present halogen generator 20.
[0085] FIG. 3 illustrates the electrolytic cell 24 in isolation.
The bipolar cell 24 comprises the bipolar electrode 30 positioned
between the cathode 96 and the anode 98. In the illustrated
embodiment, the bipolar electrode 30, cathode 96, and anode 98 each
have generally circular, disc-like shapes and are arranged in
parallel along the common central axis 100. The electrode 30, the
cathode 96, and the anode 98 desirably have a diameter of less than
about 10 inches (25.4 cm), more preferably less than about 5 inches
(12.7 cm), and most preferably equal to about 2.5 inches (6.35 cm).
It is understood, however, that the electrode 30, cathode 96 and
anode 98 can have any of a variety of other diameter sizes in order
to suit a specific application and in order to give the anode 98
and cathode 96 a proper current density.
[0086] As described in detail below, both the cathode 96 and the
anode 98 are mounted in a fixed rotational relationship within the
cell assembly 22, while the bipolar electrode 30 rotates
therebetween. In this manner, the bipolar electrode 30 functions as
a pump impeller as described below.
[0087] The cathode 96 includes a circular plate 102 that defines a
central bore 104 for the passage of water from the water inlet 46
of the volute 34 through the plate 102. The cathode plate 102 is
made of an electrically conductive, corrosion resistant material.
In the illustrated embodiment, the cathode plate 102 is made of
316L stainless steel or any other suitable metal, such as, for
example copper or titanium. The cathode plate 102, however, also
can be formed of a discontinuous material for enhancing scale
removal from the cathode 96.
[0088] The thickness of the cathode plate 102 desirably ranges
between about 0.020 and about 0.250 inches (0.0508 cm-0.635 cm),
and preferably equals about 0.032 inches (0.0813 cm). A thinner
cathode plate has more flexibility than a thicker plate, and
flexure of the plate 102 tends to promote scale removal. In
addition, in the case where the cathode plate 102 moves away from
the volute 34, as described below, the surface of the cathode plate
102 which faces the volute 34 preferably is coated to prevent scale
buildup thereon. The side of the cathode plate 102 which faces the
bipolar electrode 30, however, desirably is uncoated and can be
polished to an Ra surface finish of 8 to 16, which has been found
to reduce scale formation on this inner surface of the cathode
plate 102.
[0089] The cathode 96 desirably includes the terminal post 58 which
is electrically connected to the cathode plate 102. The terminal
post 58 has a diameter of approximately 0.125 inches (0.318 cm) or
larger; however, it is understood that the post 58 can have any of
a variety of diameter sizes in order to suit a specific
application. As understood from FIG. 2, the terminal post 58 has a
sufficient length so as to extend through the plug 56 to expose its
outer end.
[0090] The cathode plate 102 desirably can move axially (i.e., in a
direction parallel to the central axis 100) to enhance descaling of
the cathode plate 102, as explained below. The cathode plate 102,
however, preferably is biased into a desired position for normal
operation. For this purpose, the cathode may comprise a biasing
element or mechanism 110, such as a spring, which biases the
cathode plate 102 into a first position for normal operation of the
halogen generator 20 but allows the plate 102 to move to a second
position to aid descaling of the cathode plate 102. In the
illustrated embodiment, the spring has a spring constant of about
12 pounds/inch, where the normal flow rate through the volute
assembly 26 is 1.1 gallons/min. (4.23 l/min.) and the flow rate
during a cleaning cycle is 1.7 gallons/min. (6.54 l/min.). It is
appreciated, however, that those skilled in the art will be able to
calculate the desired spring constant for a specific
application.
[0091] In the illustrated embodiment, the terminal post 58 is
welded to a disc 112 which, in turn, is welded to the spring 110.
The spring 110 provides an electrical connection between the
terminal post 58 and the cathode plate 102, as well as allows
relative movement of the cathode plate 102 toward the bipolar
electrode 30, as discussed below. The spring 110 is welded to the
cathode plate 102, about the bore 104. Heliarc welding is the
preferred method of connecting the spring 102 to the plate 102 as
it causes little deformation of the electrode plate 102. The disc
112 and spring 110 desirably have a diameter of a sufficient size
to stably support the terminal post 58 above the plate 102, yet, as
understood from FIG. 2, fit within the tubular segment 50 of the
inlet port 46.
[0092] The anode 98 also comprises a circular disc or plate 118
which includes a central bore 120. The bore 120 receives the drive
shaft 86 of the motor 28 when the cell assembly 24 is assembled, as
described below.
[0093] The anode plate 118 is preferably made of titanium or any
other suitable metal. The thickness of the anode plate 118
desirably ranges between about 0.020 and about 0.250 inches (0.0508
cm-0.635 cm), and preferably equals about 0.032 inches (0.0813 cm).
The anode plate 118 is coated with precious metal oxides or other
materials, such as, for example, a mixture of ruthenium oxide and
titanium oxide, to promote the production of halogens through
electrolysis.
[0094] The anode also includes the terminal post 84 which is
electrically connected to the anode plate 118. The terminal post 84
is positioned on the plate 118 so as to extend through the volute
plate hole 82 (FIG. 2) when assembled.
[0095] The post 84 has a diameter of about 0.125 inches (0.318 cm)
or larger, and is welded to an outer edge of the anode plate 118.
It is understood, however, that post 84 can have any of a variety
of diameter sizes in order to suit a specific application. As
understood from FIG. 2, the terminal post 84 has a sufficient
length so as to extend through the hole 82 in the volute plate 36
to expose its outer end.
[0096] As seen in FIG. 3, a stationary vane or baffle 122 extends
out of the plane of the anode plate 118. The baffle 122 can be
either integrally formed with or separately formed from the anode
plate 118 and is positioned to extend radially across the plate
118. In the illustrated embodiment, the baffle 122 comprises an
integral tab which is bent out of the plane of the plate 118 to lie
at an angle transverse to the plane of the plate 118.
[0097] FIG. 3 also illustrates the bipolar electrode impeller 30 of
the electrolytic cell 24. The bipolar electrode 30 includes a
circular disc 124 which preferably is made of titanium or any other
suitable material. Various suitable coatings (e.g., precious metal
oxides) for promoting the electrolytic production of halogens may
be applied to the exterior surfaces of the bipolar electrode body
124. In the illustrated embodiment, the electrode disc 124 is
coated with a mixture of ruthenium oxide and titanium oxide.
[0098] The electrode 30 is attached to the end of the motor drive
shaft 86 so as to rotate between the anode and cathode plates 98,
96. In the illustrated embodiment, the disc 124 includes a central
aperture 126 which has a complementary shape to the shape of the
stud 90 on the end of the drive shaft 86. That is, the aperture 126
generally has a circular shape with a pair of opposing flats which
gives the aperture 126 a generally flatten-elliptical shape.
[0099] The nonconductive nut 92 holds the electrode impeller disc
124 onto the end of the drive shaft 86, as described above.
[0100] As understood from FIG. 3, the electrode plate 124 desirably
carries a plurality of small tabs 128 on the side of the plate 124
which faces the cathode 96. The tabs 128 are spaced apart from one
another and are positioned at various locations about the disc 124,
both in terms of angular and radial positions relative to the
center of the plate 124. The tabs 128, however, desirably lie
generally tangential to the rotation direction of the electrode
plate 124. This orientation of the tabs 124 minimizes the frontal
area of the tabs 128 as the tabs 128 rotate with the plate 124
through the water, thereby minimizing the drag the tabs 128 produce
on the electrode plate 124.
[0101] The tabs 128 help reduce scale buildup on the cathode 96,
especially in extremely hard water (e.g., hardness levels of 700
ppm and above). The tabs 128 contact large scale buildup on the
cathode plate 102 and effectively chop the scale from the cathode
plate 102. The sharp comers of the tabs 128 provide excellent
abrading tools, and the tabs 128 are desirably left uncoated to
enable oxide formation thereon to increase the abrasive quality of
the tabs 128.
[0102] It should be understood, however, that the electrode
impeller 30 can sufficiently descale the cathode 96 without the
tabs 128 in water having normal to moderately high hardness levels
(i.e., 300 ppm to 700 ppm). The addition of the tabs 128 thus
improves the operation of the halogen generator 20 in extremely
hard water.
[0103] As best seen in FIG. 3A, the tabs 128 are spaced about the
center of the plate 124 at various distances from the plate center.
In the illustrated embodiment, the plate 124 includes three tabs
128. The tabs 128 desirably are integrally formed with the plate
124 and are punched out to extend generally normal to the plane of
the plate 124; however, it is contemplated that the tabs 128 could
be separately formed and attached to the plate 124 in a known
manner, such as, by spot welding, cementing, etc. The tabs 128 are
positioned away from the center of the plate 124 at positions
generally corresponding to a quarter of the radius, a half of the
radius, and the full radius of the plate 124. Of course, other
numbers and placements of the tabs 128 are possible.
[0104] As understood from FIGS. 3 and 3A, the electrode impeller 30
includes a plurality of curvilinear vanes 130 which are carried on
and secured to the surface of the electrode plate 124 which faces
the cathode 96. The vanes 130 are shaped and positioned so as to
induce rotational movement of the water within the central cavity
40 of the volute 34. In the illustrated embodiment, the vanes 130
generally extend from the center of the electrode plate 124 and
extend toward the periphery of the plate 124 in a spiral fashion.
Each vane 130 includes a rounded inner end 132 and a tapering outer
end 134 which generally conforms to the outer circular periphery of
the bipolar electrode plate 124. The vanes 130 have a generally
rectilinear cross-sections with flat surfaces facing the cathode
96. The vanes 130 desirably are about 0.100 inches thick with sharp
edges formed between the sides and the flat surfaces.
[0105] The impeller vanes 130 desirably are made from plastic or a
resilient material with PVC or other suitable polymer. The vanes
130 alternatively may be made of a metallic material, such as
aluminum, and coated with a nonconductive, wear-resistant
coating.
[0106] As seen in FIG. 3, the electrode plate 124 desirably
includes a plurality of apertures 136 located on a side of the disc
124 that faces the cathode 96 to secure the vanes 130 to the plate
124. The apertures 136 are sized and positioned to receive pins 138
on the underside of a plurality curvilinear impeller vanes 130. In
FIG. 3, the vanes 130 are shown exploded to better illustrate the
pins 138 and the apertures 136 of the electrode plate 124.
[0107] The pins 138 may be press-fit into the apertures 136 and/or
may be secured within the aperture 136 by partially deforming the
ends of the pin 138 in a fashion similar to a rivet, either by
melting or peening. The pins 138 also can be mechanically bonded,
chemically bonded, or welded to a collar positioned on the opposite
side of the electrode plate 124. It is also contemplated that the
vanes 130 can be bonded to the electrode plate 124, in the
alternative or in addition to attaching the pins 138 to the plate
124.
[0108] Generator Assembly With reference to FIG. 2, the terminal
post 58 of the cathode 96 is inserted through the tubular segment
46 and the plug 56 to expose an outer end of the of the terminal
post 58. A conventional retainer ring or like fastener (not shown)
snaps onto the exposed end of the terminal post 58 to couple the
cathode with the volute 34. The terminal post 58 may also be bonded
to the plug 56 to secure the cathode 96 to the volute 34. A fluid
seal is provided within the cathode plug 56 with, for example, an
O-ring (not shown).
[0109] In this position, the cathode plate 102 desirable rest flush
against the inner wall of the volute 34 with its central hole 104
coaxially positioned relative to the opening of the inlet port 46
(i.e., the tubular segment 50). The disc 112 and spring 110 of the
cathode 96 are housed within the tubular segment 50 of the inlet
port 46.
[0110] As understood from FIG. 2, a conductor 140 leading from a
negative terminal 142 of the control unit 1 electrically connects
to the outer end of the terminal post 58 to supply electricity to
the cathode plate 102. The control unit 1 and its operation will be
discussed below.
[0111] The motor 28 is attached to the volute plate 36, for
example, by threading the elongated bolts 94, which pass through
the motor body, into the threaded inserts 66 positioned on the
outer side of the volute plate 36. So attached, the motor shaft 86
extends through the center hole 70 of the volute plate 36. A
conventional mechanical pump seal 74, such as the type available
commercially from Cyclam of France, is seated in the counterbore 72
on the inner side of the volute plate 36. The seal 74 creates a
fluid-tight seal between the volute plate 36 and the motor shaft
86, while producing little friction or interference with the motor
shaft 86 as it rotates.
[0112] The anode plate 118 is seated on the volute plate 36 with
its terminal post 84 extending through the corresponding hole 82 in
the volute plate 36. A conventional retainer ring or like fastener
(not shown) snaps onto an exposed end of the terminal post 84 to
secure the anode 98 to the volute plate 36. The volute plate hole
82 includes a fluid seal, such as an O-ring (not shown), to prevent
fluid from exiting the cell through the hole 82. A conductor 144
leading from a positive terminal 146 of the control unit 1
electrically contacts the outer end of the terminal post 84 to
supply electricity to the anode plate 118.
[0113] The bipolar electrode plate 124 is attached to the end of
the shaft 86 by the nonconductive nut 92. Specifically, the plate
124 is inserted over a portion of the shaft 86 to rest on the
shoulder 88 of the stud 90 of the shaft 86. The corresponding
shapes of the aperture 126 in the electrode plate 124 and the shaft
stud 90 key these components 86, 124 together to cause the
electrode plate 124 to rotate with the motor shaft 86. The
nonconductive nut 92 holds the electrode plate 124 on the end of
the shaft 86. In this manner, the shaft 86 generally is
electrically isolated from the other components in the electrical
system. Fortunately, the motor armature usually is already
insulated.
[0114] The volute plate 36 is placed on the end of the volute 34
with the electrode impeller 30 and anode 98 being inserted into the
interior cavity of the volute 34. In this position, the anode plate
118, electrode plate 124 and cathode plate 102 lie generally
parallel to one another. Bolts (not shown), passed through the
corresponding bolt holes 44, 80 in the lugs 42 of the volute 34 and
in the outer flange 78 of the volute plate 36, cooperate with nuts
(not shown) to hold the volute 34 and volute plate 36 together.
[0115] When assembled, the electrode plate 124 desirably is equally
distanced from the cathode plate 102 and the anode plate 118. The
gap spacings between the electrode plate 124 and the anode plate
118 and between the electrode plate 124 and the cathode plate 102
desirably is sufficient to promote efficient electrolysis. That is,
the gap spacings are set so as to maximize the efficiency of the
electrolytic cell 24. In the illustrated embodiment, the gap
spacings range between about 0.15 and about 0.75 inches, and
preferably equal about 0.15 inches. The gap spacings, of course,
can be selected in order to suit a specific application.
[0116] The spacing between the outer surface of the vanes 130 on
the rotary electrode 30 and the cathode plate 102 importantly also
are tightly controlled, especially for operation in hard water
(i.e., water having a hardness of greater than 700 ppm). In the
illustrated embodiment, the outer surfaces of the vanes 130 are
spaced from the cathode plate 102 by a distance which preferably
ranges between about 0.03 and about 0.1 inches (0.0762 cm-0.254
cm), more preferably ranges between about 0.03 and about 0.05
inches (0.0762 cm-0.127 cm), and most preferably equals about 0.03
inches (0.0762 cm). Although the vanes 130 are placed in close
proximity to the cathode plate 102, the vanes 130 do not contact
the cathode 96 when the electrode plate 124 rotates.
[0117] The close spacing between the vanes 130 and the cathode
plate 102 prevents scale buildup on the cathode 96. As the bipolar
electrode 30 rotates, the fluid velocity created at the surface of
the cathode plate 102 by the vanes 130 substantially prevents scale
from building up. Scale may temporarily form on the surface of the
cathode plate 102, but the velocity of the water within the cell
24, and in particular, between the vanes 130 and the surface of the
cathode plate 102, breaks the scale away from the plate surface
102. Water flow through the cell 24, which is produced by the vanes
130, carries the loose scale particles through the outlet port 48
of the volute assembly 26 to flush the scale particles from the
cell assembly 22. In addition, the vanes 130 will mechanically
knock-off any scale deposits in excess of the gap spacing between
the vanes 130 and the cathode plate 102.
[0118] From surface friction, the flat bottom surface of the
bipolar electrode 30 also creates some rotational velocity of the
water between the bipolar electrode 30 and the anode 98. The baffle
122, however, substantially inhibits water from rotating close to
the surface of the anode 98. This helps prevent erosion of the
anode 98. The baffle 122 also inhibits the formation of substantial
scale deposits on the underside of the bipolar electrode 30 which
functions as a cathode. Like the vanes 130 on the opposite side of
the rotary electrode 30, the baffle 122 lies close to the underside
of the electrode 30. The close spacing between the baffle 122 and
the electrode plate 124 causes a rapid change of water velocity
between the rotating electrode 30 and the stationary baffle 122. In
the illustrated embodiment, the outer surface of the baffle 122 is
spaced from the rotary electrode 30 by a distance which preferably
ranges between about 0.03 and about 0.1 inches (0.0762 cm-0.254
cm), more preferably ranges between about 0.03 and about 0.05
inches (0.0762 cm-0.127 cm), and most preferably equals about 0.03
inches (0.0762 cm). Although the baffle 122 is placed in close
proximity to the electrode plate 124, the baffle 122 does not
contact the electrode plate 124 as the plate rotates 124.
[0119] This small gap in which the water velocity changes from the
rotational speed of the electrode 30 to zero velocity at the
stationary baffle 122 greatly prevents the development of scale
buildup on the underside of the electrode 30, much like the action
between the vanes 130 and cathode plate 102. Scale may temporarily
form on the cathodic surface of the electrode 30, but the velocity
of the water within the cell 24, and in particular, between the
baffle 122 and the cathodic surface of the electrode 30, breaks the
scale away to be flushed out of the cell assembly 22. In addition,
scale buildup on the cathodic surface of the electrode 30 in excess
of the gap spacing between the baffle 122 and the electrode plate
124 is knocked off by mechanical contact with the baffle 122.
[0120] Control Unit
[0121] FIG. 4 shows a simplified illustration of the control unit 1
to indicate some main components, their principal interconnections
and their positions with respect to the sensor probe 6. A more
detailed illustration of the control unit 1 according to the
present invention is shown in FIG. 5.
[0122] The control unit 1 operates the generator 20 via the power
supply 2 according to characteristics obtained from the sensing
system, i.e., the sensor probe 6, the optional temperature sensor
13, and the optional pH sensor integrated with the sensor probe 6.
For this purpose, the control unit 1 houses a potentiostat 156 of
the amperometric sensor for amperometric measurement. The
potentiostat 156 is connected to the sensor probe 6. More
particularly, the potentiostat 156 is connected to three sensor
probe electrodes, namely a working electrode 150, a counter (or
auxiliary) electrode 152 and a reference electrode 154. The control
unit 1 further comprises a reference voltage unit 160, which
provides several reference voltages to the potentiostat 156, and a
microcontroller 162 which is, for example, a 8-bit CMOS
microcontroller PIC16C72 available from Microchip Technology
Inc.
[0123] As described below in detail, the microcontroller 162 is
coupled to the potentiostat 156, to the reference voltage unit 160,
via a capacitor and a solenoid operated switch (not shown) to the
working electrode 150 of the sensor probe 6, and to a diagnostic
system 166 which is also housed in the control unit 1. The
diagnostic system 166 is additionally connected, via a solenoid
operated switch (not shown) to the reference electrode 154 of the
sensor probe 6. The microcontroller 162 has several other inputs
and outputs which are connected to the power supply unit 2 and to
the optional temperature sensor 13, as shown in FIG. 1. These
inputs and outputs are generally indicated as port 164 in FIG.
4.
[0124] A more detailed illustration of the control unit 1 is shown
in FIG. 5 in which the sensor probe 6 is generally indicated by
means of a connector having connecting ports +5 V, GND, WRK, REF,
AUX, I/O, CS and CLK, which will be described below in connection
with FIG. 10. The control unit 1 comprises a first multiplexer 194
that is used as an interface between the microcontroller 162, the
potentiostat 156 and the reference voltage unit 160. A second
multiplexer 189 interfaces the potentiostat 156 and the diagnostic
system 166.
[0125] The multiplexers 194, 189 desirably are dual 4-channel
analog multiplexers MM74HC4052 available from National
Semiconductor. Each multiplexer 194, 189 has two sections X, Y. The
X section includes a first set of inputs X0-X3 and a respective
first output X. The Y section includes a second set of inputs Y0-Y3
and a respective second output Y. The multiplexer 194 also includes
several control outputs A, B and INH which control selection of one
of the X0-X3 inputs to the X output and also controls the selection
of one of the Y0-Y3 inputs to the Y output. Furthermore, the
multiplexers 194, 189 can be operated bidirectionally, i.e., a
signal fed to an "output" X, Y is output at an "input" X0-X3,
Y0-Y3.
[0126] Each multiplexer 194, 189 connects together the outputs of
four switches in two sections, thus achieving a pair of 4-channel
multiplexers. A binary code placed on the control inputs A and B
determines which switch in each four channel section is "on",
connecting one of the four inputs in each section to its common
output X or Y. The inhibit control input INH when high disables all
switches to their off state. In the illustrated embodiment, the
control input INH is permanently grounded thereby enabling the
switches to the "on" state. Further details can be obtained from
the corresponding data sheet.
[0127] The potentiostat 156 comprises a plurality of operational
amplifier devices. In FIG. 5, four operational amplifier devices
illustrated as a follower 170, an inverter 172, a
current-to-voltage converter 174 and a summing inverter 188, as
well as their electrical interconnections are indicated. Details of
the operational amplifier devices 170, 172, 174, 188 will be
described below in connection with FIG. 6. The potentiostat 156 can
be accomplished with a lesser number of operational amplifier
devices, for example, two operational amplifier devices, as also
described below.
[0128] In the illustrated embodiment (FIG. 5), the potentiostat 156
also comprises a low pass filter 186 and an amplifier 185. The low
pass filter 186 is positioned in series between the
current-to-voltage converter 174 and the amplifier 185. The low
pass filter 186 serves to block frequencies above a cut-off
frequency, i.e., an AC component present in the output signal of
the amplifier device 174 is blocked.
[0129] The low pass filter 186 included in the potentiostat 156 is
preferably an active filter of second order. Such an active filter
comprises two serial resistors, two capacitors and an operational
amplifier. The two resistors have values in the range of about 1
Mega Ohms and the two capacitors have values in the range of about
0.1 Micro Farad. The two resistors are connected between the output
of the operational amplifier device 174 and the non-inverting input
of the operational amplifier of the filter 186. One terminal of the
first capacitor is connected to the input of the operational
amplifier and its other terminal is grounded. One terminal of the
second capacitor is connected between the two resistors and its
other terminal is connected the inverting input of the operational
amplifier. The inverting input is also connected to the operational
amplifier output. Of course, other types of low pass filters can
also be used.
[0130] An output of the amplifier 185 is connected to an output
158b of the potentiostat 156 and to a first port of a resistor 191.
A second port of the resistor 191 is connected to an output 158a of
the potentiostat 156 and to a first port of a diode 193, its second
port being grounded.
[0131] The microcontroller 162 desirably includes a RAM, three
timer/counters, a 5-channel high-speed 8-bit AID converter (not
shown) associated with analog ports AN0-AN4, and a variety of
input/output ports RA, RB, RC, SDI, SDO. Further details are
provided in the data book PIC16C7X DATA SHEET available from
Microchip Technology Inc. The microcontroller 162 is grounded (port
VSS) and connected to a +5 volts power supply (port VDD).
[0132] The control unit 1 further comprises a shift register 196
which is a 8-bit shift register with output latches, such as that
available from National Semiconductor, as part number MM74HC595.
The device contains an 8-bit serial-in, parallel-out shift register
that feeds an 8-bit D-type storage register. Further details can be
obtained from the corresponding data sheet. The shift register 196
has eight outputs O0-O7, and its inputs include a serial data input
SER and two clock inputs SRCLK, RCLK. The outputs O5, O6 of the
shift register 196 are connected to the second multiplexer 189 (A,
B) and the outputs O0-O4 are connected to a display 198. Because
the microcontroller 162 has a limited number of input/output ports,
the shift register 196 is used to provide additional output ports
for the microcontroller 162.
[0133] The display 198 desirably comprises five light emitting
diodes (LEDs), each connected to an output O0-O4 of the shift
register 196 and to a serial resistor (not shown) connected to a +5
volts power supply. It will be understood by those skilled in the
art that the display 198 can also take a variety of other forms,
such as, for example, a liquid crystal display (LCD) device. The
display 198 indicates continuously or only on request if the
concentration of bromine is within or out of the preset range, if
the motor and/or the cell are currently active, or an error code to
facilitate maintenance of the system.
[0134] A memory device 190 comprised in the control unit 1
desirably is an electrically erasable programmable read-only memory
(EEPROM), for example, a Microchip 93LC46 EEPROM, and stores a
variety of information, including, but not limited to parameters
used for reset operations, the duration of cell usage, the number
of cell on-cycles and other system information, as described below.
In the illustrated embodiment, the control unit 1 includes the
memory device 190; however, those skilled in the art will
appreciate that the system information stored in the memory device
190 can be also stored at other locations such as, for example, in
a memory positioned within the probe 6 as described below in
connection with FIGS. 9A, 10. In this case, the memory device 190
can be omitted.
[0135] The control unit 1 further comprises a crystal oscillator
200 which is connected to the microcontroller 162 and serves as a
clock reference for the microcontroller 162.
[0136] The above-mentioned components of the control unit 1 are
interconnected to each other, as described below. The inputs Y2, Y3
of the first multiplexer 194 are connected to outputs of the
reference voltage unit 160, and the input Y0 is grounded. The input
Y1 is connected to an output 199a of a voltage follower 199 which
has an input 199b connected to an output of the reference voltage
unit 160. The output Y is connected to the inputs X0, X1, X2 of
this multiplexer 194, and to an input 183a of an inverter 183. An
output 183b of the inverter 183 is connected to the input X3 of the
multiplexer 194. The output Y is further connected to an input 168
of the potentiostat 156, which is connected to the summing inverter
188. The output X of the multiplexer 194 is connected to an input
AN2 of the microcontroller 162. The multiplexer's control input A
is connected to a microcontroller output RB3, and the control input
B is connected to a microcontroller output RB2.
[0137] With reference to the second multiplexer 189, the input X0
is connected to the input Y2 and to the counter electrode 152. The
inputs X1, X2, X3 are not used in the illustrated embodiment.
Because the second multiplexer 189 can be operated bidirectionally,
the output X functions as an input for the second multiplexer 189,
and the inputs X0-X3 function as outputs. As illustrated, the
"input" X is connected to an output 172a of the inverter 172 which
is included in the potentiostat 156. The inputs Y0, Y3 are
grounded, together with the control input INH. The input Y1 is
connected to a switch 181b for connecting either the input Y1 or
the follower 170 to the reference electrode 154. The switch 181b as
well as a second switch 181a are controlled by a solenoid 181. By
activating the solenoid 181, the microcontroller 162 can switch the
control unit 1 from a measurement mode to a conductivity mode, as
described below. The switch 181a connects either the
current-to-voltage converter 174 or an output RC2 of the
microcontroller 162 to the working electrode 150. The output Y is
connected to an input 166a of the diagnostic system 166 having an
output 166b which is connected to an input AN3 of the
microcontroller 162. The control input A is connected to an output
06 of the shift register 196, and the control input B is connected
to an output 05 of the shift register 196. An output O7 of the
shift register 196 is connected to the solenoid 181 in order to
forward control signals from the microcontroller 162. The remaining
outputs O0 . . . O4 of the shift register 196 are connected to the
display 198. A serial data input SER of the shift register 196 is
connected to a microcontroller output RB7 which outputs a data
signal DATA. A clock input SRCLK is connected to a microcontroller
output RB6 which outputs a clock signal CLK; and a clock input RCLK
is connected to a microcontroller output RB0.
[0138] The crystal oscillator 200 is connected to microcontroller
inputs OSC1 and OSC2 and oscillates at a frequency of 3.579 MHz.
The microcontroller 162 uses this frequency to generate a
low-frequency signal (e.g., 5.7 kHz) which is output at the output
RC2 and fed to a port of the switch 181 a which connects the
working electrode 150 either to the output RC2 or to the
current-to-voltage converter 174.
[0139] An input AN4 of the microcontroller 162 is connected to an
output 192a of a voltage control unit 192. The output of the
voltage control unit 192 is approximately +4.5 volts if the power
supply provides -5 volts, and goes down to zero when the power
supply for the electrical circuits does not provide the required -5
volts.
[0140] The EEPROM 190 has a clock input CLK which is connected to
the microcontroller output RB6, and has a data input DI which is
connected to the microcontroller output RB7. Furthermore, the
EEPROM 190 has an output DO which is connected to a microcontroller
input RC0, and has an input CS which is connected to a
microcontroller output RC1.
[0141] A microcontroller input RA4 is adapted to receive signals
originating from the power supply unit 2. The microcontroller 162
also generates a reset signal RST on a port RB5, and a control
signal STROBE on a port RB4, both of which are provided to the
power supply 2 (see FIG. 7).
[0142] Further, the microcontroller 162 has input/output ports RC7,
SDO, SDI, SCK which are connected to a communication interface 187.
Additional sensors, such as for temperature, pH or spa activity may
be connected to the communication interface 187.
[0143] The output 158a of the potentiostat 156 is connected to an
input ANO of the microcontroller 162, and the output 158b of the
potentiostat 156 is connected to an input 193a of an inverter 193.
An output 193b of the inverter 193 is connected to an input ANI of
the microcontroller 162.
[0144] The microcontroller 162 has an input/output port RC6 that is
connected to the input/output port I/O of the probe 6, and an
output RB1 that is connected to the port CS of the probe 6.
[0145] FIG. 6 illustrates the details of the potentiostat 156. In
the illustrated embodiment, the potentiostat 156 comprises the
operational amplifier devices 170, 172, 174, 188. (The low pass
filter 186 and the amplifier 185 (FIG. 5) are not shown.) Each
operational amplifier device 170, 172, 174, 188 comprises an
operational amplifier and some additional electrical components
such as resistors and/or capacitors. Those skilled in the art will
understand that operational amplifiers can operate in various
operational modes depending on the electrical components and their
connection to the operational amplifier. In the simplified block
diagram of FIG. 6, each operational amplifier is associated with
one or more resistors and indicated as a block to assist the
understanding. Those skilled in the art usually refer to such a
block simply by means of its function, for example, inverter or
follower.
[0146] The operational amplifier of the first operational amplifier
device 170 is in an operational mode known as follower and has a
non-inverting input 180 connected to the reference electrode 154 of
the probe 6 and has an output 182. The inverting input of the
follower is connected to its output. As seen in FIG. 6, the
operational amplifier of the second operational amplifier device
172 is in an operational mode known as inverter and has an
inverting input 176 and an output 178 which is connected to the
counter electrode 152. The non-inverting input of the inverter is
grounded. The inverting input 176 is connected to an output 171 of
a third operational amplifier device 188, its operational amplifier
is in an operational mode known as summing inverter. The inverting
input 169 of the operational amplifier is connected to the output
182 and to the input 168. The third operational amplifier device
188, i.e., the summing inverter, outputs a voltage which is the
negative sum of input voltages received from the output 182 of the
follower and the input 168 of the potentiostat 156 from the
reference voltage unit 160. The inverter of the second operational
amplifier device 172 with gain of -1 receives this negative sum and
outputs a positive voltage that is fed to the counter electrode
152. This voltage causes a current flow between the working
electrode 150 and the counter electrode 152. In this manner, the
potentiostat 156 is used to keep the potential between the working
and reference electrodes 150, 154 at a desired constant value. For
sensing bromine, this value preferably is in the range between -0.5
and +0.4 volts. More preferably within the range -0.1 and +0.3
volts, and most preferably within the range of +0.2 and +0.3 volts.
In an exemplary embodiment, the potential between the working and
reference electrodes 150, 154 is maintained at +0.3 volts. The
desired potential to be maintained between the working and
reference electrodes 150, 154 for sensing other sanitizing agents
(e.g., other chemical species) can be readily determined
empirically using well-known analytical technologies associated
with conventional amperometry.
[0147] The operational amplifier of the fourth operational
amplifier device 174 is operated in an operational mode know as
current-to-voltage converter. Therefore, the operational amplifier
device 174 is subsequently referred to as I/V converter
(current-to-voltage converter). It has an inverting input 184
connected to the working electrode 150 and has an output which is
the output 158 of the potentiostat 156. The non-inverting input of
the I/V converter 174 is also essentially grounded and serves to
maintain the working electrode 150 at ground potential. That is,
although not actually grounded, the IV converter 174 maintains the
working electrode 150 at a virtual ground for all practical
purposes. The IV converter 174 provides at the output 158 a voltage
proportional to the current flow between the working electrode 150
and the counter electrode 152.
[0148] The output 182 of the follower 170 and the input 169 of the
adder 188 are connected to the input 168 of the potentiostat 156 to
which a desired voltage is applied in order to sense a specific
sanitizing agent. For instance, a voltage of about +300 millivolts
(mV) is applied to sense bromine. With this voltage applied at the
input 168, the potentiostat 156 generally stabilizes the voltage
between the reference electrode 154 and the working electrode 150
generally equal to +0.3 volts for sensing bromine.
[0149] The feedback loop, which includes the reference electrode
154 and the follower 170, causes the potentiostat 156 to compensate
for variations in the impedance across the working and counter
electrodes 150, 152 which are due to factors other than the
fluctuating concentration levels of the particular sanitizing agent
being sensed. The high impedance created by the follower 170 within
the feedback loop though insures that practically no current flows
through the feedback loop. Then the current flow between the
working and counter electrodes 150, 152, and thus the impedance
through the electrolyte will be a function of the targeted
sanitizing agent concentration in the spa water.
[0150] As mentioned above, the potentiostat 156 can include only
two operational amplifiers devices. In such a circuit, an input of
the first operational amplifier device is connected to the working
electrode 150 and operates as current-to-voltage converter, as
described above. An output of the second operational amplifier
device is connected to the counter electrode 152, and the inverting
input of the second operational amplifier device is connected to
the reference electrode 154. The non-inverting input of the second
operational amplifier device receives the applied voltage.
[0151] Power Supply Unit
[0152] FIG. 7 shows an illustration of the power supply unit 2
shown in FIG. 1. The power supply unit 2 desirably comprises an
opto-coupler unit 202 and a shift register unit 204. The
opto-coupler unit 202 has several inputs for electrical control
signals such as the CLK, DATA, RST and STROBE received from the
microcontroller 162 (see FIG. 5), and a like number of outputs
which are connected to inputs of the shift register unit 204.
[0153] The shift register unit 204 includes an 8-bit shift register
with output latches such as a MM74HC595 available from National
Semiconductor (see above), and a Schmitt Trigger IC, for example,
an MM74HC14 available from National Semiconductor having six
inverting Schmitt Trigger. The Schmitt Trigger IC shapes the
electrical control signals CLK, DATA, RST and STROBE output from
the opto-coupler unit 202 before they are input to the shift
register. Data bits are clocked into the shift register according
to the control signal CLK, and output from the shift register
according to the control signal STROBE. Signals output from the
shift register control the generator 20 shown in FIG. 1. These
signals include MOTOR ON/OFF, H/L SPEED and CELL ON/OFF
signals.
[0154] Although the meanings of the signals MOTOR ON/OFF, H/L SPEED
and CELL ON/OFF are believed to be self-explanatory, a short
description is given:
[0155] MOTOR ON/OFF controls the motor 28 between active and
inactive states;
[0156] H/L SPEED controls the rotational speed (high or low) of the
motor 28 and therefore controls the water flow rate through the
cell 24; and
[0157] CELL ON/OFF controls the cell 24 between energized and
deenergized states.
[0158] The power supply unit 2 additionally comprises first and
second power control units 206, 210. The first power control unit
206 is connected to the shift register unit 204 and receives the
signals MOTOR ON/OFF and H/L SPEED and additionally receives a
signal RAMP. The first power control unit 206 desirably includes an
AC to DC converter to convert AC line current to direct current.
Outputs of the first power control unit 206 are connected to the
motor 28 (shown in FIGS. 2 and 7). The second power control unit
210 is also connected to the shift register unit 204 and receives
the signal CELL ON/OFF. Additionally it receives the signal RAMP.
The second power control unit 210 also includes an AC to DC
converter to convert the AC line current to direct current.
Positive and negative outputs 142, 144 of the second power control
unit 210 are connected to the cell 24 (shown in FIGS. 2 and 7). The
first power control unit 206 interfaces a line power source (e.g.,
120 volts) with the motor 28, and inter alia, transforms the line
voltage to one or more lower voltages and controls the voltages or
currents applied to the motor 28. Likewise, the second power
control unit 210 connects a line power source (e.g., 120 volts) to
the cell 24, inter alia, transforms the line voltage to one or more
lower voltages and controls the voltages or currents applied to the
cell 24.
[0159] The power control units 206, 210 receive the signal RAMP
which represents the charging voltage across a capacitor in a ramp
generator 203. The charging is triggered at each zero crossing of
the power line voltage occurring at a frequency of 100 Hz/120 Hz
(i.e., twice the power line frequency). The zero crossings also
serve as a time base for a conventional watchdog timer (not shown)
in the automatic sanitizing system 12. A conventional zero crossing
detector 205 can be implemented, for example, using a diode bridge
and a current limiting resistor.
[0160] The power supply unit 2 also includes first and second
detector units 208, 212. The first detection unit 208 is coupled to
the motor 28 and to the microcontroller 162. In the illustrated
embodiment, the detection unit 208 comprises a voltage amplifier to
amplify a motor signal received from the motor 28, and two
comparators to compare the amplified motor signal with different
preset threshold values. One comparator detects a high motor
current and the other detects if no motor current is present. The
amplifiers desirably are included in integrated circuits, such as
that available from National Semiconductor, as part number LM324A.
The detection unit 208 monitors the operation of the motor 28, and
detects if the current is too high or too low (e.g., zero). The
unit 208 in response to these detections generates a signal which
indicates the operational condition of the motor (e.g., "motor
current high" or "no motor current") and provides the signal to the
microcontroller 162 for further processing.
[0161] Similarly, the detection unit 212 includes a voltage
amplifier and two comparators monitors. The voltage amplifier
amplifies a cell signal received from the cell 24, and the two
comparators compare the amplified cell signal with different preset
threshold values. One comparator detects a high cell current and
the other detects if a low cell current is present. The detection
unit 212 thus monitors the operation of the cell 24, and detects if
the current is too high or too low (e.g., zero). The unit 212 in
response to these detections generates a signal which indicates the
operational condition of the cell (e.g., "cell current low" or "no
cell current") and provides the signal to the microcontroller 162
for further processing.
[0162] The signals from the detection units 208, 212 desirably are
not directly input to the microcontroller 162. As seen in FIG. 7, a
shift register 207 and an opto-coupler unit 201 act as an interface
between the detection units 208, 212 and the microcontroller 162.
In the illustrated embodiment, the shift register 207 which
receives its clock signal from the microcontroller 162 is a 8-bit
serial shift register such as a 74HC165 available from National
Semiconductor. The shift register 207 shifts parallel input data to
a serial (inverting) output 209 which is connected to the
opto-coupler unit 201. An output of the opto-coupler unit 201 is
connected to the input RA4 of the microcontroller 162. In the
illustrated embodiment, the opto-coupler units 201, 201 form part
of and are housed within the power control unit 2; however, the
opto-coupler units 201, 202 can also be positioned outside the
power control unit 2, i.e., between the power supply unit 2 and the
microcontroller 162.
[0163] The opto-coupler unit 201 converts an electrical signal
received from the shift register 207 to an optical signal, for
example, by means of a photodiode, and then back to an electrical
signal, for example, by means of a phototransistor. In the same
manner, the opto-coupler unit 202 converts received electrical
control signals first to optical signals and then back to
electrical signals. By means of the opto-coupler units 202, 201 the
control unit 1 and the power supply unit 2 are electrically
isolated from each other so that no common ground exists between
them. Further details regarding such an isolation will be explained
in greater detail in connection with FIG. 15.
[0164] Two outputs from each detection unit 208, 212 are connected
to shift register inputs 211, 212, 213, 217. These inputs 211, 212,
213, 217 receive the signals generated by the detection units 208,
212, and the shift register 207 serially outputs the signals to the
microcontroller 162.
[0165] Another shift register input 215 communicates with the spa
jet pump (either a booster pump or a high speed setting on the main
spa pump) so that it receives a signal when the spa jet pump are
activated. This signal is also forwarded to the microcontroller 162
which detects the spa usage.
[0166] Sensor Probe
[0167] FIGS. 8A through 10 illustrate a preferred embodiment of the
sensor probe 6 used in the automatic sanitizing system 12. An
exploded view of the sensor probe 6 is shown in FIG. 8A. The
following description uses the terms "front" and "rear" in
describing various components of the probe 6. These terms are used
in reference to the water flow through water circulation line 9,
such that "front" implies proximate to the water flow and "rear"
implies distal of the water flow.
[0168] A tube 248, which has a front end 246 and a rear end 250,
desirably forms a body of the sensor probe 6. The front end 246
fits into a receptacle of an adapter 224. The adaptor has a
reduced-diameter, threaded front nipple 222 that threads into a
threaded receptacle 220 of a T-fitting 218. The T-fitting 218 also
includes two side ends 214, 216 adapted to be integrated into the
water circulation line 9 shown in FIG. 1. In the illustrated
embodiment, the ends 214, 216 include barbed nipples which insert
into flexible hoses that desirably form a portion of the
circulation line 9.
[0169] A cap 258 is attached to the rear end 250 of the tube 248,
and a cup- or cylinder-shaped rubber boot 260 covers an outer end
of the cap 258. The cap 258 comprises a first cavity of a first
diameter and a second cavity of a second diameter; the first
diameter desirably is larger than the first diameter so that an
annular shoulder is formed on the inner wall and an annular recess
and a corresponding annular shoulder is formed on the outer wall of
the cap 258.
[0170] Internally, the sensor probe 6 comprises a PC board 254 and
an electrical connector 256 (e.g., a RJ-45 socket) located near the
tube rear end 250. Advantageously, the PC board 254 comprises a
memory 257 for storing measurement characteristic of the probe 6.
The connector 256 desirably is mounted on a side of the PC board
254 that faces the rubber boot 260, and the PC board 254 is
attached to the cap 258 by fasteners, such as for example, by a
pair of screws 252. The electrical interconnection between the
memory 257 and the connector 256 is shown in FIG. 10 and will be
described below.
[0171] The sensor probe 6 comprises an end plug 234 positioned near
the front end 246 of the tube 248. The plug 234 includes several
hollow, tube-shaped elements 232, 228, 230 of different diameters
and lengths. The openings of the elements 232, 228, 230 desirably
extend generally parallel to a longitudinal axis of the tube 248.
Two of the openings 228, 230 are adapted to receive two rod-shaped
amperometric electrodes, specifically the working electrode 150 and
the counter electrode 152. The other opening is adapted to receive
a plug 226.
[0172] As illustrated in FIG. 8B, the end plug 234 can also include
at least one additional opening 236 for receiving a pH sensing
glass electrode 238 of the optional pH sensor. Such a pH sensor can
be part of the mentioned sensing system. This additional opening
236 desirably lies next to one of the openings 228 that receive one
of the amperometric electrodes and to the opening 232 that receives
the plug 226.
[0173] The working and counter electrodes 150, 152 desirably have
similar cylindrical shapes of the same diameter and length. The
length of each electrode 150, 152 is longer than the respective
tubular element of the end plug 234 to extend beyond the ends of
the end plug, as described below.
[0174] The electrodes 150, 152 are made of an electrically
conductive material. In the illustrated embodiment, the electrodes
150, 152 are made, at least in part, of a carbon-based material,
such as, for example, graphite or glassy carbon.
[0175] One wire receptacle 240, 242 is attached to each electrodes
150, 152 on an end of the respective electrode that faces the
tubular body 248 of the probe 6. Each receptacle 240, 242 makes
electrical contact with the respective electrode 150, 152 and
receives an unshielded end of a shielded wire or conductor that
connects the respective electrode 150, 152 to the connector 256 on
the PC board 254, as described below. In this manner, the connector
256 located on one end of the probe 6 electrically communicates
with both electrodes 150, 152 positioned on the opposite end of the
probe 6 (i.e., the working end of the probe 6). As an alternative
to the wire receptacles 240, 242, a conductive epoxy can be used to
bond a wire to a electrode 150, 152.
[0176] The probe 6 also includes the reference electrode 154
located between the front end plug 234 and the rear cap 258 within
the tubular body 248. In the illustrated embodiment, the reference
electrode 154 extends from the PC board 254 toward the tube front
end 246.
[0177] The reference electrode 154 is desirably made of a
silver/silver chloride wire embedded in a potassium chloride (KCl)
saturated gel as an electrolytic solution. The gel is preferably
comprised of about 25% glycerol and about 75% KCl solution 3.5
molar with a suitable gelling agent such as methylcellulose (e.g.,
METHOCEL available from Dow Chemical). The gel material is
schematically illustrated in FIG. 9A and 9B by a cross-hatching
that includes bubbles, which is representative of a chemical
solution; however, the gel desirably does not include gaseous
bubbles.
[0178] The plug 226 closes the large opening in the end plug 234 to
prevent an ingress of water into the electrolytic solution within
the tubular body 248 of the probe 6. In the illustrated embodiment,
the plug 226 desirably is made of a porous material, such as, for
example, a porous glass or porous TEFLON, or wood, and functions as
a membrane allowing the passage of electrons. Of course, other
materials having such a characteristic (e.g., a salt bridge) can be
used for the plug 226.
[0179] The other components of the sensor probe 6 such as the
T-fitting 218, the adapter fitting 224, the end plug 234, the tube
248 and the cap 258 are made of suitable materials, such as, for
example, but without limitation, acrylonitrile-butadiene-styrene
(ABS) or other polymers and plastics, which are transparent or non
transparent and desirably are generally resistant to chemicals such
as bromine, chlorine and hydroxides. A desirable material
advantageously would also be durable, light-weight and relatively
easy to manufacture. Furthermore, these components can be
constructed in a variety of ways which will be well known to one
skilled in the art. For example, these components can be integrally
molded such as by injection molding.
[0180] FIG. 9A illustrates a rear portion of an assembled sensor
probe 6; components which have been already mentioned in FIG. 8A
have the same reference numerals. The cap 258 is attached to the
tube 248 by a suitable adhesive or by other suitable means, such as
press-fitting in combination with a sealant.
[0181] The connector 256 is mounted on a side of the PC board 254
facing the rubber boot 260; and the PC board 254 is attached to the
cap 258 by the screws 252. Shielded wires 247, 249 are connected
(e.g., soldered) to wire leads on a side of the board 254 that
faces the tube front end 246. The wires 247, 249 extend through the
gel in the tubular body 248, and as understood from FIG. 10, the
opposite ends of the wires 247, 248 are connected to the electrodes
150, 152 by the wire receptacles 240, 242, respectively.
[0182] The reference electrode 154 is also attached (e.g.,
soldered) to a wire lead on the PC board 254. The reference
electrode 154 depends from the PC board 254, through the gel in the
tubular body 248, and as seen in FIG. 10, desirably terminates at a
location near the end cap plug 226.
[0183] Although not illustrated, the glass pH electrode 238 (FIG.
8B), which can be contained in the end plug 234, is also connected
to the PC board 254 by a third shielded wire. The wire extends
through the gel in the tubular body 248 and a wire receptacle,
which is similar to illustrated wire receptacles 240, 242, connects
the wire to the pH electrode.
[0184] In this manner, the PC board 254 not only functions as a
substrate on which to mount the electrical connector 256, the
memory 257 and wire leads, to which the shielded wires 247, 249 and
the reference electrode 154 are attached, but also serves to create
a circuit between terminals of the connector 256 and the respective
wire leads; however, any of a variety of other ways, which would be
well known to those skilled in the art, can also be used to
interconnect together the wires and the connector, as well as to
support these components at the rear end of the sensor probe 6.
[0185] With reference to FIG. 9A, both sides of the PC board 254,
the screws 252, part of the connector 256 and the wire ends are
embedded or potted in epoxy or another suitable material thereby,
inter alia, electrically insulating the soldering points on the PC
board 254 from each other. This potted assembly also generally
seals the components from the gel within the tubular body 248 as
well as from ambient air and water which may enter the outer end of
the cap 258.
[0186] The rubber boot 260 covers an outer end of the cap 258.
Because of the rubber boot's elasticity, it slips over the cap 258
and stays there without an additional securing. The rubber boot 260
has a central opening 253 through which a data transmission line
255 is inserted and connected to the connector 256. The connection
is preferably achieved by means of a RJ-45 socket connector and a
corresponding jack 251 attached to the data transmission line 255.
This allows easy attachment of the data transmission line 255 to
the sensor probe 6 and additionally facilitates replacement of the
sensor probe 6. The data transmission line 255, however, can be
attached directly to the PC board 254, for example, by means of
soldering.
[0187] FIG. 10 illustrates how the memory 257 and the connector 256
are electrically interconnected. The eight pin connector 256 is
attached to the data transmission line 255 which is connected to
the control unit 1 shown in FIG. 1. The eight pins of the connector
256 are referenced as P1-P8. Three pins P6-P8 are connected to the
electrodes 150, 152, 154 (indicated through reference numerals at
the corresponding pins).
[0188] The memory 257 is preferably an electrical erasable
programmable ROM (EEPROM), for example, a Microchip 93LC46 EEPROM
providing 256 bytes of nonvolatile storage. The EEPROM 93LC46 has
eight pins; seven pins are used in the illustrated embodiment: A
chip select input CS is connected to pin P2, a clock input CLK is
connected to pin P3 and a data input DI is connected to pin P4. Via
a resistor R, a data output DO is also connected to pin P4. Under
certain circumstances (e.g., the last bit of the address is a "1"),
the microcontroller could source current to ground via the
microcontroller. The resistor R limits this current to a reasonable
level. To provide power to the EEPROM 257, a pin VCC is connected
to pin 1 and a pin VSS is connected to pin P5 (ground). In use, a
voltage of +5 volts is applied to the EEPROM 257. Between pins VCC
and VSS, a capacitor C is positioned to short-cut interfering high
frequency voltage components. A pin DRB is connected to pin
VCC.
[0189] As explained above, the EEPROM 257 included in the probe 6
stores data specific for each probe 6; details of the specific data
will be explained in connection with FIGS. 14A, 14B. The EEPROM 257
can also store data (duration of cell usage) provided by the
microcontroller during operation of the system.
[0190] When the probe 6 is connected to the control unit 1 shown in
FIG. 4 for the first time, the characteristic data will be read
into the microcontroller memory. The EEPROM 257 and the
microcontroller communicate serially and bidirectionally via a
three-wire bus using a synchronous (clocked) communication
protocol. During a read operation, the microcontroller sends a code
word and an address to the EEPROM 257 from which data will be read.
The EEPROM 257 activates the data output DO and the probe specific
data is read into the microcontroller.
[0191] FIG. 9B illustrates a front portion of an assembled sensor
probe 6; components which have been already mentioned in FIG. 8A
have the same reference numerals. The front end 246 of the tube 248
is inserted into the adapter fitting 224 and is fixed therein by
glue or another adhesive, or by other suitable means.
[0192] The adapter 224 is also fitted into the end plug 51; the
openings of end plug elements 232, 228, 230 contain the two
amperometric electrodes 150, 152 and the plug 226. (An additional
opening 236 can contain the pH electrode 238, as illustrated in
FIG. 8B). The amperometric electrodes 150, 152 and the plug 226 are
glued into the openings 232, 228, 230. As illustrated in FIG. 10,
the ends of the electrodes 150, 152 are exposed relative to the end
plug 224 to be in contact with water flowing through the fitting
218 at the working end of the probe 6. The lengths of the
electrodes 150, 152 are shorter than the lengths of the tube-shaped
openings 228, 230, i.e., the electrodes 150, 152 are fully inserted
into the openings 228, 230. Also, the wire receptacles 240, 242,
which connect the shielded wires 247, 249 to the electrodes 150,
152, are inserted into the openings 228, 230. The rear ends of the
openings 228, 230 are then sealed or potted with epoxy thereby
insulating the amperometric electrodes 150, 152 from each other and
from the reference electrode 154. (The pH electrode 238 can be
secured and potted within the end plug 234 in a similar
manner).
[0193] The threaded nipple 222 of the adapter 224 is inserted to
the threaded base end opening 220 of the T-fitting 218. The side
ends 216, 214 of the T-fitting 218 are each inserted into a tube
which is part of the water circulation line 9 shown in FIG. 1. Hose
clamps 213, 215, one at each side end 216, 214, secure hoses, which
form part of the circulation line 9, to the barbed ends 214, 216 of
the fitting 218.
[0194] In addition to housing the working, counter and reference
electrodes 150, 152, 154 of the amperometric sensor, the probe 6
also forms a pH sensor probe. The pH sensing glass electrode 238
and the reference electrode 154 together function to form the pH
sensor cell. The signal from the pH electrode is transferred via
the connector 256 and the data transmission line 255 to the control
unit 1 to convert the signal into a pH value which can be
displayed. The pH value can also be used to control activation of a
solenoid valve of a dispenser unit (not shown) to dispense a pH
buffer (either in liquid or crystallized form).
[0195] Operation of the Automatic Sanitizing System
[0196] A blended salt composition comprising sodium chloride and
sodium bromide is added to the spa water in which both dissolve.
The salt composition comprises at least 4 percent by weight of
sodium bromide and at least 75 percent by weight of sodium
chloride. More preferably, the salt composition comprises at least
10 percent by weight of sodium bromide and at least 90 percent by
weight of sodium chloride. The salt composition is added to the
water so as to produce at least about 50 ppm sodium bromide and at
least about 500 ppm sodium chloride in the resulting aqueous
solution in the spa 7; desirably the aqueous solution comprises
about 50 ppm to 120 ppm sodium bromide and about 1000 ppm to 1200
ppm sodium chloride. To produce concentrations of sodium bromide
and sodium chloride within these ranges, the salt composition is
added to the spa water at a ratio of about 1 pound of salt to every
100 gallons of water in the spa 7.
[0197] The control unit 1 in combination with the sensor probe 6
regularly measures the concentration of bromine in the spa water
and controls the generator 20 to either start or stop the
production of bromine.
[0198] When the control unit 1 energizes the generator 20, current
flows between the negative terminal 142 and the positive terminal
144 of the power control unit 210 (see FIGS. 2 and 7). Electrical
current flows through the cathode 96, through the electrolytic
solution within the cell 24 and to the anodic surface of the
bipolar electrode 30. The electrical current also flows through the
bipolar electrode 30 to the cathodic surface of the electrode 30
and through the electrolytic solution within the cell 24 to the
anode 98. Positive and negative charges are induced on the cathodic
and anodic surfaces of the bipolar electrode 30, respectively. The
bipolar electrode 30 thus acts as an anode on its surface facing
the stationary cathode 96 and acts as a cathode on the surface
facing the stationary anode 98. The power control unit 210
desirably supplies about 2.4 amps of current to the anode 98 and
cathode 96, giving the anode and cathode a current density of about
0.08 amps/cm.sup.2.
[0199] The control unit 1 activates via the power supply unit 2 the
motor 28 when the cell 24 is energized, as discussed below. The
motor 28 drives the electrode impeller 30 in a desired direction to
produce a flow of water through the cell assembly 22.
[0200] The electrical potential imposed between the electrodes of
the cell 24 electrolytically causes the dilute halide in the water
to form pH neutral halogen, oxygen, and hydrogen, among other
compounds. For instance, when the water contains a dilute solution
of sodium chloride and sodium bromide, chlorine and oxygen are
formed at the anode 98 and hydrogen is formed at the cathode 96
within the cell 24. The chlorine then oxidizes the bromide to
elemental bromine. Once bromine is formed it can disproportionate
in aqueous solutions to form hypobromous acid and a bromide anion.
The bipolar electrode 30 and the anode 98 are sufficiently sized to
produce chlorine, and thus bromine, at desired rate of
approximately 1-2 grams per hour.
[0201] The bromine later kills algae and bacteria, and in the
process is reduced back to bromide. Through this mechanism, the
bromine is recycled over and over again; the bromide from the spent
bromine is regenerated back so that salt rarely needs to be
replenished. However, there is some loss of bromine, either caused
by "degassing" (volatilization), splash-out or other such
factors.
[0202] Control of the generator 20 in this manner automatically
maintains the concentration of bromine within a desired range of
about 2 ppm to about 6 ppm, and more preferably within the desired
range of 2.5 ppm and 3.5 ppm. The control unit 1 also starts the
generator 20 if usage of the spa is detected. For instance, in the
illustrated embodiment, when a user activates the jets a signal is
generated and input to the control unit 1 through input RA4. This
allows for early initiation of bromine production so that the
concentration of bromine will not significantly drop when people
first enter the spa 7.
[0203] An exemplary mode of operation of the automatic sanitizing
system 12 is described in connection with the flow charts
illustrated in FIGS. 11, 12, 13. These flow charts, however,
represent only a preferred way of operating. Those skilled in the
art, however, will readily appreciate that the automatic sanitizing
system 12 can be operated in any of a variety of ways.
[0204] With reference to the flow chart shown in FIG. 11A, the
operation of the automatic sanitizing system 12 starts with an
initialization of the system 12, as represented in operation block
801. The initialization is mainly controlled by the microcontroller
162 set to operate according to user or manufacturer parameters.
Such parameters include, for example, the size of the spa body, an
estimation of the amount of usage or usage factor, or other such
parameters. These parameters allow the control unit 1, and more
specifically the microcontroller 162, to determine the duty cycle
time. The initialization may also include reading probe specific
data from the EEPROM 257 located within the end portion of the
probe 6.
[0205] The control system from this point forward operates through
a generally continual series of duty cycles until the control
system is taken off line (i.e., turned off). The following
describes the control operation through a single duty cycle. It is
to be understood that the same sequence of steps desirably is
performed in each duty cycle. Thus, the description herein of one
will be understood as a universal description of all of the duty
cycles preformed by the control system.
[0206] The duty cycle begins by turning off (i.e., deenergizing)
the cell 24, if active, and turning on the motor 28, as represented
in operation block 802. This is specifically accomplished by
applying the corresponding control signals DATA, CLK and RST to the
power supply unit 2. The mentioned turning "off" or "on" of the
motor 28 or cell 24, as it will be understood by those skilled in
the art, means that a voltage or a current of sufficiently high
amount to enable operation is applied or cut off. This can be
achieved through a variety of means, for example, opening or
closing an electrical switch and thereby connecting or
disconnecting the motor 28 or cell 24 to a voltage or current
source; or operating an output of an integrated circuit between a
high or low state.
[0207] The initial act of starting the pump motor 28 of the
generator 20 (operation block 802) represents the start of a
measurement cycle during which the sanitizing agent (e.g., bromine)
concentration is determined. The motor 28 is active for one minute
and desirably circulates about 1.5 gallons per minute (5.775 liter
per minute), as represented in operation block 803. As long as one
minute has not elapsed, the system checks for motor 28 faults, as
represented in block 812. The detection units 208, 212 (FIG. 7)
provide the signals "motor current high", "no motor current", "cell
current low" and "no cell current". Each of these signals can be
input to the microcontroller input RA4 for further processing. In
case such a signal is received, i.e., a specific state or fault has
been detected (decision block 813), a fault code is displayed, as
represented in operation block 814. This fault code informs the
user of the fact that a fault has been detected and of the kind of
fault, for example, no cell current. As a consequence of the
detected fault, the microcontroller 162 shuts down the power supply
for the cell 24, as represented in operation block 815. Next, the
system falls into an idle mode, as represented in operation block
816, until the user repairs and resets the system.
[0208] In the preferred embodiment of the present invention, the
actual measurement of the bromine concentration in the spa water,
as represented in operation block 808, takes place after one minute
has elapsed and if no faults are detected. The required reference
voltage for sensing bromine (+300 mV) is applied to the sensor
probe 6 during one minute. The microcontroller 162 initiates a code
word to be applied to the multiplexer control inputs A, B to switch
one selected reference voltage to the output Y. This voltage (+300
mV) is then applied to the input 168 of the potentiostat 156 and
fed to the counter electrode 152 of the sensor probe 6 via the
multiplexer 189 ("input" X, "output" X0). The measurements are
ignored until the end of the one minute cycle. At the end of one
minute, the microcontroller 162 takes 256 measurements and averages
them. Each measurement results in a current indicative of the
concentration of bromine in the spa water; the current is converted
to a voltage by the I/V converter 174 of the potentiostat 156 and
fed to the microcontroller 162 which processes the sensor probe
signal, inter alia, through the internal A/D converter.
[0209] In the preferred embodiment of the control unit 1, positive
and negative voltages originating from the sensor probe signal can
be processed:
[0210] If the voltage is positive, a positive voltage (output 158a)
is fed to the input ANO. The positive voltage (output 158b) is also
fed to the inverter 193 which outputs a negative voltage that is
fed to the input AN1. This negative voltage, however, will not be
processed.
[0211] If the voltage is negative, a negative voltage (output 158a)
is fed to the input ANO, but will not be processed. The negative
voltage (output 158b) fed to the inverter 193 is converted into a
positive voltage and fed to input AN1.
[0212] After determining the bromine concentration, the
microcontroller 162 again initiates the application of the required
reference voltage (+300 mV) to the sensor probe operation working
electrode 150; the reference voltage is also measured, as
represented in block 804. The measurement of the reference voltage
is made by the microcontroller 162 which receives the selected
reference voltage from the output X of the multiplexer 194. Since
the output Y of the multiplexer 194 is directly connected the
inputs X0, X1, X2, and via the inverter 183 to the input X3, by
selecting one reference voltage a corresponding input X0-X3 is
addressed and switched through to the output X. If the reference
voltage is not equal to +300 mV, as represented in decision block
805, the system initiates a fault code which is displayed
(operation block 814) and the idle mode is begun (operation blocks
815, 816). In such a case, the previously taken bromine
measurements are dropped.
[0213] If the applied reference voltage equals +300 mV, the system
measures the negative power supply, for example, -4.3 volts for the
potentiostat 156, as represented in operation block 806. The
microcontroller 162 measures the voltage output from the voltage
control unit 192 connected to the input AN4. A failure of this
requirement (see decision block 807) also leads to the display of a
fault code (operation block 814) and to the subsequent shut down
(operation block 815) of the cell 24 and the start of the idle mode
(operation block 816).
[0214] It should be understood that the described voltage
measurements (operation blocks 804, 806) are optional; however,
these diagnostic steps insure that the system is operating
properly. For instance, loss of the negative power supply of -4.3
volts to the operational amplifier devices of the potentiostat 156
may falsely indicate that the concentration of bromine in the spa
water is too low, for example, zero.
[0215] The measurement of bromine is followed by an optional
measurement of the spa water temperature, as represented by
operation block 809. At this step, the microcontroller 162 receives
a signal from the communication interface 187 which is connected to
the temperature sensor 13. The microcontroller 162 uses the
temperature measurements to eventually correct the current
measurements for changing water temperature caused by, for example,
intense solar irradiation or heating. As noted above, the
temperature measurement is optional depending on the requirements
regarding the accuracy of the bromine readings and the resulting
control of the generator 20. In the illustrated embodiment of the
automatic sanitizing system 12, the microcontroller 162 can be
programmed to use temperature readings or to perform the control
without such readings.
[0216] After this temperature measurement, the microcontroller 162,
via the power supply unit 2, turns off the motor 28, as represented
in operation block 810, after it has been active for one minute.
This action constitutes the end of the measurement cycle.
Advantageously, during the measurement cycle the cell 24 is turned
off, i.e. no voltage is applied and consequently no electrolysis
takes place.
[0217] The microcontroller 162 uses the measured current flowing
between the working electrode 150 and the counter electrode 152 as
a control parameter during a control cycle, as represented by
operation block 811; this control cycle will be explained below in
connection with FIG. 12.
[0218] A cleaning cycle, as represented by blocks 817-826 in FIG.
11B, is employed to clean the sensor probe 6. The cleanness of the
exposed electrodes 150, 152 of the sensor probe 6 directly
influences the reliability of the current measurements because the
chemical reactions occur at the surfaces of these electrodes 150,
152. Any deposition of salt and/or algae alters the electrical
characteristic of the electrodes 150, 152. Therefore, adequate
cleaning helps to achieve reliable current measurements and
subsequently reliable bromine concentration readings. Also, as
described above, the positioning of the sensor probe 6 downstream
of the generator 20, as shown in FIG. 1, helps to minimize algae
deposition.
[0219] The cleaning cycle desirably starts after the control cycle.
As represented by operation block 817 and decision block 819, a
positive potential of +1 volt is initially applied during the
cleaning cycle between the working electrode 150 and the counter
electrode 152 for one minute. Secondly, as represented by operation
block 820 and decision block 822, a negative potential of -100
millivolts is applied between the working electrode 150 and the
counter electrode 152, also for one minute. And thirdly, as
represented by operation block 823 and decision block 825, a
positive potential of +300 mV is applied between the working
electrode 150 and the counter electrode 152 for one minute. This
sequence is repeated five times, as represented by decision block
826; no measurements are taken during this fifteen minute cycle.
The application of the different voltages is controlled by the
microcontroller 162 which controls the multiplexer 194 (code words
applied to control inputs A, B) to alternatingly switch different
voltages from the inputs Y0-Y3 to the output Y. Those skilled in
the art will recognize that other voltage sequences can be applied
to clean the electrodes of the sensor probe 6.
[0220] The described cleaning cycle generates an oxidizing species
and thereby cleans the electrodes of the sensor probe 6 of any salt
build-up. After five sequences have elapsed, the next duty cycle
begins (at operation block 802).
[0221] Each time one of the three different potentials is applied,
a check cycle starts, as represented by operation blocks 818, 821
and 824. One example of such a check cycle is explained in
connection with the flow chart shown in FIG. 13, which will be
described below.
[0222] As noted above, the measurement cycle is followed by a
control cycle (block 811) which is illustrated by the flow chart
shown in FIG. 12. The control cycle, as represented by blocks
901-912, is described using the current flowing between the working
electrode 150 and the counter electrode 152 as a control parameter
since the measured current directly correlates with concentration
of the measured species (e.g., bromine), although the potentiostat
156 outputs a voltage. However, those skilled in the art will
recognize that the control cycle can be equally described using the
voltage output from the potentiostat 156 or a digital value
calculated by the microprocessor 162.
[0223] As described above, the microcontroller 162 receives the
sensor probe signal, which corresponds to the current, for internal
processing. If the current is above the upper threshold, as
represented by decision blocks 902 and 903, the microcontroller 162
outputs control signals that are fed to the power supply unit 2 to
stop the production of bromine by turning off the cell 24, as
represented by operation block 904. The upper threshold limit is
stored in the memory 190 and retrieved by the microcontroller 162
during this control cycle. Additionally, the microcontroller 162
controls the display 198, as represented by operation block 905,
indicating that the concentration of bromine is above the desired
concentration of, for example, 3.5 ppm, and that the cell 24 has
been turned off. The motor 28 and the cell 24 will be shut down for
15 minutes. After that time, the concentration of bromine is
measured again during the next duty cycle. The cleaning cycle
desirably runs during this down time; however, the cleaning cycle
need not be nested within the control cycle as these cycles are not
interdependent.
[0224] If the current is below the lower threshold, as represented
by decision block 902, the microcontroller 162 outputs signals that
the power supply unit 2 receives to start production of bromine by
turning on the cell 24, as represented by operation block 910. Like
the upper threshold limit, the lower threshold limit is stored in
memory 190 and is retrieved by the microcontroller 162 during this
portion of the control cycle. Also, the microcontroller 162
controls the display 198, as represented by operation block 911,
indicating that the concentration of bromine is below the desired
concentration, for example, 2.5 ppm, and that the cell 24 has been
turned on. The cell 24 desirably runs for 15 minutes.
[0225] The production of bromine also begins when the current is
between the upper and lower threshold and the cell 24 was activated
during the immediately preceding duty cycle, as represented by
decision blocks 902, 903, and 906 and operation block 909. Also,
the microcontroller 162 controls the display 198 to indicate that
the concentration of bromine is within the desired range, as
represented by operation block 908.
[0226] If the current is between the upper and lower threshold and
the system was not turned on during the last duty cycle, as
represented by decision blocks 902, 903, 906, the microcontroller
162 controls the display 198 to indicate that the concentration of
bromine is within the desired range, as represented in operation
block 907.
[0227] The foregoing control mode of the cell 24 insures that when
the bromine concentration falls below a desired level (e.g., 2.5
ppm), the control system will raise the concentration level up to
or slightly more than a desired upper level (e.g., 3.5 ppm).
However, once a concentration level near the upper limit is
reached, the system will maintain the cell 24 in an inactive state
while the bromine concentration level falls through the desired
preset range (e.g., 3.5 ppm to 2.5 ppm). In this manner, the
control system does not constantly activate the cell 24 and cause
the bromine concentration level to fluctuate above and below only
one of the preset range limits.
[0228] A flow chart of the check cycle (FIG. 11, blocks 818, 821,
824) is shown in FIG. 13. When the cell 24 and motor 28 have been
active for a cumulative period of three hours, as represented by
decision blocks 1002, 1003, the electrodes of the cell 24 will be
cleaned, as represented by operation block 1004. As described
above, the memory 190 stores the duration for which the motor 28
and the cell 24 have been operated. The microcontroller 162 inputs
data into this memory 190 and retrieves data from it, for example
to start the cleaning cycle after a preset operation time. Cleaning
is, inter alia, required to remove scale from the electrodes and
thereby maintaining operability of the generator 20. There are
several ways to remove scale, as described below.
[0229] The control unit 1 (i.e., the microcontroller 162) can cause
the motor 28 to undergo rapid rotational directional reversals
several times at regular intervals during the check cycle or to
periodically reverse the rotational direction of the impeller 30
during its operational cycle. For instance, during each scale
removal sequence, the control unit 1 causes the motor 28 to rotate
the electrode impeller 30 in one direction for 15 seconds, then
reversed to rotate the electrode impeller 30 in an opposite
direction for another 15 seconds. This reversal is repeated six
times during the scale removal sequence.
[0230] Rapid reversals of the rotational direction of the bipolar
electrode 30 have been found to cause scale deposits within the
cell 24 to be quickly removed. The rapid reversals in the bipolar
electrode's rotational direction create rapid water flow reversals
relative to the stationary cathode 96. These water flow reversals
also are present relative to the lower surface of the bipolar
electrode 30 by virtue of the stationary baffle 122. Such flow
reversals generate turbulence adjacent the cathodic surfaces within
the cell 24 to swirl and knock off scale growth before it can
affect the efficiency of the cell 24.
[0231] The ability of the cathode plate 102 to move toward the
rotary electrode 30 also can be used for scale removal. With
reference to FIG. 2, the spring 110 allows the cathode plate 102 to
be displaced in an axial direction within the cell 24. The cathode
plate 102 is mounted at an optimum spacing with respect to the
bipolar electrode 30 for efficient electrolysis with the spring 110
in a relaxed, undeflected state. As the pressure within the cell 24
changes, the cathode plate 102 is displaced toward the electrode
30.
[0232] During the cell cleaning step (operation block 1004), the
motor 28 drives the electrode impeller 30 for about 30 seconds at a
high rate of speed to generate a lower pressure at its surface
facing the cathode 96, thus urging the cathode plate 102 toward the
bipolar electrode 30 and against the bias of the spring 110.
Excessive scale buildup on the cathode plate 102 will contact the
vanes 130 or tabs 128, thus cleaning the cell 24 automatically. As
the motor 28 slows down, the cathode plate 102 returns to the
optimum spacing from the electrode 30 for efficient electrolysis.
This high speed cleaning cycle can be easily accomplished with a
minimum of electric circuitry.
[0233] This cleansing is done each time the cell 24 and the motor
28 have been operated for three hours.
[0234] If three hours have not yet elapsed and the cell 24 and the
motor 28 are active, as represented by blocks 1002, 1003, or the
cleaning has been done, as represented by block 1004, the current
to the motor 28 and the current to the cell 24 are checked, as
represented by block 1005, which provide important information for
maintenance. For instance, no cell current or no pump current can
indicate disconnection from the power supply.
[0235] The control unit 1 in combination with the power supply unit
2 monitor the current draw of the motor 28 of the generator 20. As
scale builds up on the electrode surfaces within the cell 24, the
motor 28 experiences more drag and additional loading. This added
load translates into a current increase through the motor 28 which
is monitored. The control unit 1 may alternatively implement a
descaling cycle when the current increases by a preset percentage,
such as, for example, a 20% increase from normal current draw of
the motor 28.
[0236] Sensing the motor current will also indicate a problem with
loss of fluid prime within the generator 20. If there is no fluid
in the cell assembly 22, the motor 38 will experience a dramatic
reduction in load and associated decrease in current flow. A
significant drop of motor current, such as, for example, 50% or
greater, may be indicative of a loss of prime. In such a case, the
control unit 1 should deenergize the generator 20. Occasionally,
massive scale buildup followed by a cleaning cycle will dislodge a
large quantity of scale leading to a clog which can "seize" small
motors. In this situation, the control unit 1 can sense the rapid
increase in current draw by the motor 28 and trigger a rapid series
of motor reversals to dislodge the clog.
[0237] In all of these cases, the current through the motor 28 is
detected in conventional ways and this information is used by the
control unit 1 to instigate the various responses described. The
specific circuit diagrams and logic used and briefly described
above are shown in a black-box manner in FIG. 7 and believed within
the scope of experience of one skilled in the motor feedback and
control art.
[0238] The current through the cell 24 may also be monitored as a
means of determining the timing and duration of cell operation.
More specifically, as scale builds up, the cell current will
decrease. In this situation, the control unit 1 will run the cell
24 for a longer period than normal to compensate for the reduced
halogen concentration generated by a less than efficient, or scaled
cell. Optionally, the operation of the cell 24 may coincide with
the operation of the spa jet booster pump or air injection blower
to increase the halogen generation in periods of increased
need.
[0239] An increased need due to spa usage can also be detected
during the check cycle, as represented by block 1006. The automatic
sanitizing system 12 is adapted to receive, via the shift register
207 shown in FIG. 7, a signal indicating that the spa jets are
active, i.e., the spa 7 is used. If a usage is detected, the
microcontroller 162 starts producing bromine by activating the cell
24, as represented by block 1007. It is optional, if the production
of bromine is immediately started after the usage is detected or if
a certain time delay of a few minutes is applied.
[0240] Diagnostic System
[0241] In a preferred embodiment of the automatic sanitizing system
12, the proper operation of the sensor probe 6 can be monitored.
This is achieved through the diagnostic system 166 included in the
control unit 1, as shown in FIG. 5. The diagnostic system includes
a diagnostic unit and a voltage sensor as described below. The
diagnostic system 166 determines if the conductivity between the
working electrode 150 and the reference electrode 154 decreases;
i.e., if the conductivity through the sensor probe plug 226 (FIG.
8A) decreases.
[0242] For this determination, a low or medium frequency signal in
the range of 4 kHz to 10 kHz is used; preferably it is a 5.7 kHz
square wave signal with no DC component which is applied to a
voltage divider. The microcontroller 162 outputs at its output RC2
a 5.7 kHz square wave signal having a 2 volts DC component which is
fed to a capacitor (not shown) to block the 2 volts DC component.
If the square wave signal is to be applied, the microcontroller 162
energizes the solenoid 181 that operates the switch 181a to connect
the working electrode 150 to the output RC2 via the capacitor. The
working electrode 150 receives the square wave signal. Furthermore,
the solenoid 181 operates the switch 181b to connect the reference
electrode 154 via the input Y1 of the multiplexer 189 to the
diagnostic system 166. Through this, a voltage divider is created
consisting of an impedance between the working electrode 150 and
the reference electrode 154, and an internal resistor which is part
of the diagnostic system 166. This results in a sensible voltage
across the internal resistor having a square wave function, its
magnitude depends on the magnitude of inter-electrode impedance.
The resulting voltage is rectified using a precision full-wave
rectifier. An output of the rectifier is connected to a capacitor
to filter any AC component from the resulting voltage, and to the
input AN3 of the microcontroller 162. A change in the
inter-electrode impedance causes a change in the DC voltage fed to
the internal AID converter of the microcontroller 162 and can
indicate that the plug 226 is clogged, or that the working
electrode 150 surface has plated out, or that the salt
concentration in the spa water is too low. In such a case, the
microcontroller 162 can display a code indicating that service is
required and/or initiate counter measures, such as resetting the
sensor probe 6.
[0243] Operation of the Potentiostat
[0244] The operation of the potentiostat 156, as shown in FIGS. 5,
6 is best understood by keeping in mind that an operational
amplifier reacts in the manner required to maintain zero potential
difference between its inputs. Thus, a stable state for a loop
consisting of the follower 170 and the inverter 172 corresponds to
the output of follower 170 being equal in magnitude, but opposite
in polarity to the applied voltage on input 168. Since the follower
170 is in the follower configuration, its output must equal minus
the applied voltage relative to ground potential. Because the
reference electrode 154 is maintained at minus the applied voltage
and the working electrode 150 at zero volts, the potential of the
working electrode 150 relative to the reference electrode 154 is
maintained at the applied voltage.
[0245] The operational amplifiers 170, 172, 174 are advantageously
provided with an asymmetric power supply of +5 volts and a negative
potential in the range of -4.5 volts and -4.2 volts, preferably
-4.3 volts. The +5 volts potential is provided by a known voltage
regulator (see FIG. 15) and the -4.3 volts potential is provided by
a combination of a voltage regulator for -5 volts (see FIG. 15), a
4.3 volts zener diode and a serial 33 Ohm resistor. Such a negative
potential prevents the operational amplifiers 170, 172, 174 from
permanently saturating when the potentiostat 156 operates in a
pulsed mode, as used during the cleaning cycle. The reduction of
the negative power supply from the usually applied -5 volts to -4.3
volts provides recovery of the operational amplifiers 170, 172, 174
in short time, typically faster than 30 seconds.
[0246] In operation, i.e., when a voltage determined by the
electrochemical potential of bromine is applied to the sensor probe
6, a current flowing between the counter electrode 152 and the
working electrode 150 is output from the sensor probe 6 and fed to
such a potentiostat 156.
[0247] In case that a species other than bromine is to be sensed,
the control unit 1 applies a voltage determined by the
electrochemical potential of that species. This voltage is also
provided by the reference voltage unit 160 which comprises several
individual voltage units, e.g., formed by voltage dividers
connected to +5 volts or -5 volts. Alternatively, a reference
voltage can be generated with a Zener diode and a serial resistor,
as well known in the art.
[0248] The reference voltage unit 160 used in the preferred
embodiment of the invention can be adapted to output the voltage
required for the species. Such an adaption can be done, for
example, by changing an existing voltage divider or by adding an
additional voltage divider. The additional voltage divider can be
preinstalled so that only a connection to a reference voltage unit
160 output is necessary. In the preferred embodiment, the reference
voltage unit 160 provides, for example, 100 millivolts, 300
millivolts, 1 volt and 0 volt.
[0249] In FIG. 14A, a graph is shown to illustrate the sensor probe
6 current response as a function of the bromine concentration.
Illustrated is the linear current response in nanoampere (I/nA) for
the desired bromine concentration (Br.sub.2/ppm) in the range of
about 2.5 ppm and about 3.5 ppm. For the current response, a lower
and an upper threshold are defined. In the preferred embodiment of
the present invention, the lower threshold, for example, set at
1100 nA, indicates that the bromine concentration has reached 2.5
ppm and the upper threshold, for example, at 1500 nA, indicates
that the bromine concentration has reached 3.5 ppm.
[0250] In order to achieve the linear current response as a
function of bromine concentration (FIG. 14A), it has been
determined that the concentration of bromide should be at least 50
ppm. It is believed that a bromine concentration at or above this
level will cause substantially all of the hypobromous acid to react
with the bromide and produce bromine in reaching an equilibrium
state. As a result, the concentration of bromine is increased to a
level sufficient to produce a linear current response.
[0251] The particular current response of a specific probe 6 is
unique. That is, each probe 6 produces a current response at a
certain bromine concentration level which is very likely different
from a current response generated by another probe at the same
bromine concentration level. FIG. 14B shows a graph illustrating
exemplary voltage responses of three probes as a function of the
bromine concentration level (Br.sub.2/ppm). The voltage response is
proportional to the current response (see FIG. 14A) and is
generated through a current-to-voltage conversion within the
potentiostat. Each voltage response S1, S2, S3 has a different
slope, for example, the slope of the voltage response S1 of the
first probe is about 1.6 ppm/volt, the slope of the voltage
response S2 of the second probe is about 2 ppm/volt and the slope
of the voltage response S3 of the third probe is about 4 ppm/volt.
Thus, as used herein in connection with the exemplary embodiment,
"output voltage response" means the voltage converted and output by
the potentiostat in connection with a current response measured by
the amperometric sensor probe.
[0252] As discussed above, the desired concentration range for
bromine is between 2.5 ppm and 3.5 ppm, and upper and lower
thresholds for the output voltage response are defined. Thus, in
the present examples, the upper and lower thresholds (dashed lines)
for the first probe (output voltage response S1) are about 2.1
volts and about 1.5 volts, respectively. The upper and lower
thresholds (dotted lines) for the second probe (output voltage
response S2) are about 1.8 volts and 1.3 volts, respectively. The
upper and lower thresholds (dotted lines) for the third probe
(output voltage response S3) are about 0.8 volts and about 0.6
volts, respectively.
[0253] This indicates that an isolated output voltage reading
without information about the output voltage response
characteristic of a specific probe is of little use and may be
misleading. For example, an output voltage reading of 2 volts can
indicate for the second probe (output voltage response S2) that the
bromine concentration is too high. However, for the first probe
(output voltage response S1) the output voltage reading of 2 volts
indicates that the bromine concentration is still within the
desired range.
[0254] The control unit 1 (FIG. 4), therefore, desirably receives
information about the output voltage response characteristic of the
specific probe to which it is connected. The output voltage
response of a probe desirably is determined after manufacture of
the probe and stored as a look-up table in the EEPROM 257. The
EEPROM 257 can store other measurement characteristics in addition
or in the alternative to providing an output voltage response that
is unique to a particular probe. For instance, such measurement
characteristics associated with a particular probe can include, for
example, but without limitation, data related to measured
electrochemical potential (e.g., ionic or oxidation reduction
potential) versus concentration, measured current flow versus
concentration, and measured conductivity versus concentration. If
necessary, the EEPROM 257 can also store an offset value or several
data points in the event a batch of probes is nonlinear to account
for background current, as well as decay time (e.g., time necessary
for probe to stabilize within a sample before measurement taken).
The EEPROM 257 thus can store such uniquely specific data with the
particular sensor probe 6.
[0255] The measurement characteristic of the probe desirably is
determined empirically by testing the probe in a known environment.
For example, in the illustrated embodiment, a first output voltage
response is measured using a solution of a known first bromine
concentration (e.g., 2.5 ppm). At this concentration, the output
voltage is measured to provide one data point of the output voltage
response table. Through interpolation and extrapolation, further
points can be determined. For instance, by assuming that the output
voltage is zero at a bromine concentration of 0 ppm, a second data
point of the output voltage response is available. Then by assuming
a model for the output voltage response in the concentration range
between 0 ppm and known first concentration level (e.g., 2.5 ppm),
the output voltage response between the measured and assumed points
can be interpolated. In a preferred embodiment, a linear model is
used; however, other models can also be used. In addition, a
solution of a known second bromine concentration, or several other
solutions having known bromine concentrations, can be used to
determine further data points of the output voltage response. The
interpolated output voltage response desirably is then discretized
for discrete concentration values, and then stored in the look-up
table in the EEPROM 257.
[0256] The output voltage response can also be calculated by
extrapolation using the assumed model for output voltage response
and the measured and assumed data points. The extrapolated output
voltage response can then be discretized in a variety of output
voltage/Br.sub.2 pairs and stored in the EEPROM 257 in the look-up
table.
[0257] The stored output voltage response can be read into the
microcontroller, as explained above in connection with FIG. 10. In
use, when the microcontroller receives a measured voltage, the
microcontroller can associate this voltage with a stored output
voltage/Br.sub.2 pair to determine accurately the bromine
concentration.
[0258] The EEPROM 257 can also store data specific to the probe 6,
in addition to or in the alternative to a measurement
characteristic (e.g., output voltage response). For instance, the
EEPROM 257 can store information relating to the manufacturer of
the sensor probe, its serial number or possible other data, which
allow identification and interoperation of the probe with the
automatic sanitizing system illustrated in FIG. 1A. For instance,
such interoperational data can include a specific hand-shake
protocol.
[0259] Storing measurement characteristic data, and possible other
information, of a probe in an EEPROM included in the probe,
eliminates the need for normalization or calibration when a probe
is initialized or replaced in the system. An additional advantage
is that inexpensive materials (carbon based materials) can be used
for the electrodes instead of platinum or gold electrodes, which
produce more uniform measurement responses from probe to probe. The
non-uniform measurement responses uniquely associated with probes
including less expensive electrodes, can be stored with and
accompany the electrode. However, it is understood that although
the present sensor probe includes a memory device, the automated
sanitizing system will operate acceptably when conventional methods
for normalization or calibration are used instead of storing
characteristic data of the sensor probe in the probe's memory.
[0260] In FIG. 15, the general architecture of the automatic
sanitizing system 12 shown in FIG. 1 is illustrated to explain
further the electrically isolation of the power supply unit 2 from
the control unit 1. Same components have been identified by the
same reference numerals.
[0261] A transformer 402 having a primary winding 404 and two
secondary windings 406, 408 is connected to a 120/240 volts power
line. For illustration purposes, the transformer 402 is shown to be
positioned outside the power supply unit 2; however, the
transformer 402 can also be positioned within the power supply unit
2. The secondary winding 406 is connected to the power supply unit
2, and the secondary winding 408 is connected to a rectifier unit
410 that comprises a rectifier 412 and two voltage regulators 414,
416. The output of the voltage regulators 414, 416 provide +5 volts
and -5 volts, respectively, to the control unit 1 and to the probe
6 which is connected to the control unit 1. Electrical devices and
circuits used in the preferred embodiment of the present invention,
for example, the microcontroller 162, the multiplexer 194 and the
reference voltage unit 160 are coupled to the +5 volts and/or -5
volts power supply outputs of the regulators 414, 416 and are
grounded, as known in the art; although this is not always
explicitly shown in the drawings.
[0262] The power supply unit 2 is connected to the sanitizing agent
source and, via opto-coupler units 201, 202, to the control unit 1
as shown in detail in FIG. 7. Those skilled in the art will
appreciate that the opto-coupler units 201, 202 may also be located
with in the control unit 1. The power supply unit 2 comprises the
zero crossing detector 205 (FIG. 7) which is connected to the
120/240 volts power line via a further opto-coupler 400. The zero
crossing detector 205 and the detection units 208, 212 (FIG. 7) are
part of a feedback circuitry.
[0263] The opto-coupler units 201, 202, 400 and the transformer 402
electrically isolate the control unit 1 and the probe 6 from the
power supply unit 2 so that no common ground exists. That is, the
power supply unit 2 in combination with either the electrolytic
cell 20 or the dispenser 20a are electrically isolated from the
control unit 1 which is coupled to probe 6. In addition, the
opto-coupler units 201, 202 electrically isolate the control unit 1
and the probe 6 from a controlled device (e.g., either the
electrolytic cell 20 or the dispenser 20a), whose operation the
control unit 1 governs, and from the feedback circuitry, which is
formed in part by the detection units 208, 212. The isolation of
the control unit 1 (and the probe 6) from the power supply unit 2,
the feedback circuitry, and the controlled device (e.g., the cell
20) is represented by a broken isolation line 418 around the
control unit 1 and the probe 6. This isolation enhances the
accuracy of the concentration level readings obtained by the
amperometric sensor, and thus the performance of the system, to
more precisely control and maintain the level of sanitizing agent
in the water feature.
[0264] Although this invention has been described in terms of
certain preferred embodiments, other embodiments that are apparent
to those of ordinary skill in the art are also within the scope of
this invention. Accordingly, the scope of the invention is intended
to be defined by the claims that follow.
* * * * *