U.S. patent application number 10/720703 was filed with the patent office on 2004-06-03 for galvanic probes as ph and oxidation reduction potential sensors, control devices employing such probes, and related methods.
Invention is credited to Decker, Paul, Martzall, Thomas Lee, Mosley, Michael David.
Application Number | 20040104130 10/720703 |
Document ID | / |
Family ID | 25414841 |
Filed Date | 2004-06-03 |
United States Patent
Application |
20040104130 |
Kind Code |
A1 |
Mosley, Michael David ; et
al. |
June 3, 2004 |
Galvanic probes as pH and oxidation reduction potential sensors,
control devices employing such probes, and related methods
Abstract
A galvanic probe comprises a sensor electrode and a reference
electrode. The sensor electrode has an exposed surface that
comprises a noble metal or antimony or bismuth, and, optionally, an
oxide or hydroxide thereof. The reference electrode is spaced apart
from the sensor electrode and has an exposed surface that comprises
zinc or magnesium, and, optionally, an oxide or hydroxide thereof.
The probe may be incorporated into a device for controlling the pH
and/or ORP of a fluid in a vessel to a desired pH and/or ORP level,
incorporated into methods for measuring the pH and/or ORP of a
fluid, or used as a galvanic cell.
Inventors: |
Mosley, Michael David;
(Calverton Park, MO) ; Decker, Paul; (Creve Coeur,
MO) ; Martzall, Thomas Lee; (St. Charles,
MO) |
Correspondence
Address: |
THOMPSON COBURN LLP
One US Bank Plaza
St. Louis
MO
63101-1693
US
|
Family ID: |
25414841 |
Appl. No.: |
10/720703 |
Filed: |
November 24, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10720703 |
Nov 24, 2003 |
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09901807 |
Jul 10, 2001 |
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6653842 |
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Current U.S.
Class: |
205/787.5 ;
204/433 |
Current CPC
Class: |
G01N 27/4167 20130101;
G01N 27/4168 20130101 |
Class at
Publication: |
205/787.5 ;
204/433 |
International
Class: |
G01N 027/26 |
Claims
What is claimed is:
1. A galvanic probe comprising a sensor electrode having an exposed
surface comprising (1) a first material selected from the group
consisting of noble metals, antimony, and bismuth, and (2)
optionally, an oxide or hydroxide of the first material, and a
reference electrode spaced apart from the sensor electrode and
having an exposed surface comprising (1) a second material selected
from the group consisting of zinc and magnesium, and (2)
optionally, an oxide or hydroxide of the second material.
2. A galvanic probe as set forth in claim 1 wherein the first
material is selected from the group consisting of antimony and
bismuth.
3. A galvanic probe as set forth in claim 2 wherein the first
material is antimony.
4. A galvanic probe as set forth in claim 1 wherein the first
material is a noble metal.
5. A galvanic probe as set forth in claim 4 wherein the first
material is selected from the group consisting of platinum, silver
and gold.
6. A galvanic probe as set forth in claim 5 wherein the first
material is platinum.
7. A galvanic probe as set forth in claim 2, further comprising a
second sensor electrode wherein the second sensor electrode has an
exposed surface comprising a noble metal and, optionally, an oxide
or hydroxide of the noble metal.
8. A galvanic probe as set forth in claim 3 wherein the sensor
electrode is a first sensor electrode, and further comprising a
second sensor electrode wherein the second sensor electrode has an
exposed surface comprising a noble metal and, optionally, an oxide
or hydroxide of the noble metal.
9. A galvanic probe as set forth in claim 7 wherein the noble metal
is selected from the group consisting of platinum, silver and
gold.
10. A galvanic probe as set forth in claim 8 wherein the noble
metal is selected from the group consisting of platinum, silver and
gold.
11. A galvanic probe as set forth in claim 9 wherein the noble
metal is platinum.
12. A galvanic probe as set forth in claim 10 wherein the noble
metal is platinum.
13. A galvanic probe as set forth in claim 1 wherein the exposed
surface of the reference electrode comprises zinc.
14. A galvanic probe as set forth in claim 13 wherein the exposed
surface of the reference electrode consists essentially of zinc
and, optionally, zinc oxide, zinc hydroxide or both.
15. A galvanic probe as set forth in claim 13 wherein the exposed
surface of the reference electrode comprises zinc of purity in
excess of 99.9% and, optionally, zinc oxide, zinc hydroxide or
both.
16. A galvanic probe as set forth in claim 3 wherein the exposed
surface of the reference electrode comprises zinc.
17. A galvanic probe as set forth in claim 16 wherein the exposed
surface of the reference electrode consists essentially of zinc
and, optionally, zinc oxide, zinc hydroxide or both.
18. A galvanic probe as set forth in claim 16 wherein the exposed
surface of the reference electrode comprises zinc of purity in
excess of 99.9% and, optionally, zinc oxide, zinc hydroxide or
both.
19. A galvanic probe as set forth in claim 6 wherein the exposed
surface of the reference electrode comprises zinc.
20. A galvanic probe as set forth in claim 19 wherein the exposed
surface of the reference electrode consists essentially of zinc
and, optionally, zinc oxide, zinc hydroxide or both.
21. A galvanic probe as set forth in claim 19 wherein the exposed
surface of the reference electrode comprises zinc of purity in
excess of 99.9% and, optionally, zinc oxide, zinc hydroxide or
both.
22. A galvanic probe as set forth in claim 12 wherein the exposed
surface of the reference electrode comprises zinc.
23. A galvanic probe as set forth in claim 22 wherein the exposed
surface of the reference electrode consists essentially of zinc
and, optionally, zinc oxide, zinc hydroxide or both.
24. A galvanic probe as set forth in claim 22 wherein the exposed
surface of the reference electrode comprises zinc of purity in
excess of 99.9% and, optionally, zinc oxide, zinc hydroxide or
both.
25. A galvanic probe as set forth in claim 2, further comprising a
circuit, said electrodes generating a signal when the electrodes
are in contact with a fluid having a pH such that the electrodes
are in electrochemical communication with each other, the signal
being input to and processed by said circuit.
26. A galvanic probe as set forth in claim 25 wherein a voltage
differential exists between the electrodes and the signal is the
voltage differential or amperage of a current flowing through the
circuit, said current being produced galvanically by the electrodes
in interaction with the fluid.
27. A galvanic probe as set forth in claim 26 wherein said circuit
comprises a signal processor and the signal processor translates
the signal to information indicative of the pH of the fluid.
28. A galvanic probe as set forth in claim 27 wherein the signal
processor transmits the information to a display that displays the
pH of the fluid.
29. A galvanic probe as set forth in claim 28 wherein the display
is in wireless communication with the signal processor.
30. A galvanic probe as set forth in claim 26 wherein said circuit
comprises a signal processor and the signal processor translates
the signal to information indicative of an amount of a composition
that should to be added to the fluid to adjust the pH of the fluid
to a desired pH.
31. A galvanic probe as set forth in claim 30 wherein the signal
processor transmits the information to a display for displaying
data from which may be determined the amount of a composition that
should to be added to the fluid to adjust the pH of the fluid to
the desired pH.
32. A galvanic probe as set forth in claim 16, further comprising a
circuit, said electrodes generating a signal when the electrodes
are in contact with a fluid having a pH such that the electrodes
are in electrochemical communication with each other, the signal
being input to and processed by said circuit.
33. A galvanic probe as set forth in claim 32 wherein a voltage
differential exists between the electrodes and the signal is the
voltage differential or amperage of a current flowing through the
circuit, said current being produced galvanically by the electrodes
in interaction with the fluid.
34. A galvanic probe as set forth in claim 33 wherein said circuit
comprises a signal processor and the signal processor translates
the signal to information indicative of the pH of the fluid.
35. A galvanic probe as set forth in claim 34 wherein the signal
processor transmits the information to a display that displays the
pH of the fluid.
36. A galvanic probe as set forth in claim 35 wherein the display
is in wireless communication with the signal processor.
37. A galvanic probe as set forth in claim 33 wherein said circuit
comprises a signal processor and the signal processor translates
the signal to information indicative of an amount of a composition
that should to be added to the fluid to adjust the pH of the fluid
to a desired pH.
38. A galvanic probe as set forth in claim 33 wherein the signal
processor transmits the information to a display for displaying
data from which may be determined the amount of a composition that
should to be added to the fluid to adjust the pH of the fluid to
the desired pH.
39. A galvanic probe as set forth in claim 6, further comprising a
circuit, said electrodes generating a signal when the electrodes
are in contact with a fluid having an ORP such that the electrodes
are in electrochemical communication with each other, the signal
being input to and processed by said circuit.
40. A galvanic probe as set forth in claim 39 wherein a voltage
differential exists between the electrodes and the signal is the
voltage differential or amperage of a current flowing through the
circuit, said current being produced galvanically by the electrodes
in interaction with the fluid.
41. A galvanic probe as set forth in claim 40 wherein said circuit
comprises a signal processor and the signal processor translates
the signal to information indicative of the ORP of the fluid.
42. A galvanic probe as set forth in claim 41 wherein the signal
processor transmits the information to a display that displays the
ORP of the fluid.
43. A galvanic probe as set forth in claim 42 wherein the display
is in wireless communication with the signal processor.
44. A galvanic probe as set forth in claim 40 wherein said circuit
comprises a signal processor and the signal processor translates
the signal to information indicative of an amount of a composition
that should to be added to the fluid to adjust the ORP of the fluid
to a desired ORP.
45. A galvanic probe as set forth in claim 40 wherein the signal
processor transmits the information to a display for displaying
data from which may be determined the amount of a composition that
should to be added to the fluid to adjust the ORP of the fluid to
the desired ORP.
46. A galvanic probe as set forth in claim 42 wherein the oxidation
reduction potential measurements correspond to chlorine levels in
the fluid.
47. A galvanic probe as set forth in claim 12, further comprising a
first circuit, said first sensor electrode and said reference
electrode generating a first signal when said first sensor
electrode and said reference electrode are in contact with a fluid
having a pH such that said first sensor electrode and said
reference electrode are in electrochemical communication with each
other, said first signal being input to and processed by said first
circuit, and still further comprising a second circuit, said second
sensor electrode and said reference electrode generating a signal
when said second sensor electrode and said reference electrode are
in contact with a fluid having an ORP such that said second sensor
electrode and said reference electrode are in electrochemical
communication with each other, said second signal being input to
and processed by said second circuit.
48. A galvanic probe as set forth in claim 47 wherein a voltage
differential exists between each sensor electrode and the reference
electrode and the signals are the voltage differentials or
amperages of currents flowing through the respective circuits, said
currents being produced galvanically by the electrodes in
interaction with the fluid.
49. A galvanic probe as set forth in claim 48 wherein said first
circuit comprises a first signal processor, said second signal
processor translating the first signal to information indicative of
the pH of the fluid, and said second circuit comprises a second
signal processor, said second signal processor translating the
signal to information indicative of the ORP of the fluid.
50. A galvanic probe as set forth in claim 49 wherein the first
signal processor transmits the information to a display that
displays the pH of the fluid, and the second signal processor
transmits the information to a display that displays the ORP of the
fluid.
51. A galvanic probe as set forth in claim 50 wherein the display
for displaying the pH levels is a first display and the display for
displaying the ORP levels is a second display, the first display is
in wireless communication with the first signal processor and the
second display is in wireless communication with the second signal
processor.
52. A galvanic probe as set forth in claim 48 wherein said first
circuit comprises a first signal processor, the first signal
processor translating the first signal to pH-related information
indicative of an amount of a composition that should to be added to
the fluid to adjust the pH of the fluid to a desired pH, and said
second circuit comprises a second signal processor, the second
signal processor translating the second signal to ORP-related
information indicative of an amount of a composition that should to
be added to the fluid to adjust the ORP of the fluid to a desired
ORP.
53. A galvanic probe as set forth in claim 52 wherein the first
signal processor transmits the pH-related information to a display
for displaying data from which may be determined the amount of a
composition that should to be added to the fluid to adjust the pH
of the fluid to the desired pH, and the second signal processor
transmits the ORP-related information to a display for displaying
data from which may be determined the amount of a composition that
should to be added to the fluid to adjust the ORP of the fluid to
the desired ORP.
54. A device for controlling the pH of a fluid in a vessel to a
desired pH level, comprising: (a) a sensor electrode having an
exposed surface comprising (1) a first material selected from the
group consisting of antimony, and bismuth, and (2) optionally, an
oxide or hydroxide of the first material; (b) a reference electrode
spaced apart from the sensor electrode and having an exposed
surface comprising (1) a second material selected from the group
consisting of zinc and magnesium, and (2) optionally, an oxide or
hydroxide of the second material; and (c) a circuit; arranged such
that said electrodes generate a signal when the electrodes are in
contact with a fluid having a pH such that the electrodes are in
electrochemical communication with each other, the signal being
input to and processed by said circuit.
55. A device as set forth in claim 54, further comprising a signal
processor, the signal processor translating the signal to
information indicative of an amount of a composition that should to
be added to the fluid to adjust the pH of the fluid to a desired
pH.
56. A device as set forth in claim 55, further comprising a supply
of the composition and a dispenser control in communication with
the signal processor such as to receive the information, the
dispenser control causing the amount of the composition that should
to be added to the fluid to be dispensed in response to receipt of
the information.
57. A device for controlling the pH of a fluid in a vessel to a
desired ORP level, comprising: (a) a sensor electrode having an
exposed surface comprising (1) a noble metal, and (2) optionally,
an oxide or hydroxide of the first material; (b) a reference
electrode spaced apart from the sensor electrode and having an
exposed surface comprising (1) a second material selected from the
group consisting of zinc and magnesium, and (2) optionally, an
oxide or hydroxide of the second material; and (c) a circuit;
arranged such that said electrodes generate a signal when the
electrodes are in contact with a fluid having an ORP such that the
electrodes are in electrochemical communication with each other,
the signal being input to and processed by said circuit.
58. A device as set forth in claim 57, further comprising a signal
processor, the signal processor translating the signal to
information indicative of an amount of a composition that should to
be added to the fluid to adjust the ORP of the fluid to a desired
ORP.
59. A device as set forth in claim 58, further comprising a supply
of the composition and a dispenser control in communication with
the signal processor such as to receive the information, the
dispenser control causing the amount of the composition that should
to be added to the fluid to be dispensed in response to receipt of
the information.
60. A device as set forth in claim 59 wherein the oxidation
reduction potentials correspond to chlorine levels in the
fluid.
61. A method for measuring pH of a fluid, comprising placing the
electrodes of the galvanic probe of claim 28 into a fluid and
reading the pH from the display.
62. A method for measuring pH of a fluid, comprising placing the
electrodes of the galvanic probe of claim 35 into a fluid and
reading the pH from the display.
63. A method for measuring the oxidation reduction potential of a
fluid, comprising placing the electrodes of the galvanic probe of
claim 42 into a fluid and reading the oxidation reduction potential
from the display.
64. A method for measuring the oxidation reduction potential of a
fluid, comprising placing the electrodes of the galvanic probe of
claim 50 into a fluid and reading the oxidation reduction potential
from the display.
65. A galvanic cell comprising an electrolyte in contact with: a) a
sensor electrode having an exposed surface comprising (1) a first
material selected from the group consisting of noble metals,
antimony, and bismuth, and (2) optionally, an oxide or hydroxide of
the first material; and b) a reference electrode spaced apart from
the sensor electrode and having an exposed surface comprising (1) a
second material selected from the group consisting of zinc and
magnesium, and (2) optionally, an oxide or hydroxide of the second
material.
66. A galvanic cell as set forth in claim 65, wherein the first
material is selected from the group consisting of antimony and
bismuth.
67. A galvanic cell as set forth in claim 66 wherein the first
material is antimony.
68. A galvanic cell as set forth in claim 65 wherein the first
material is a noble metal.
69. A galvanic cell as set forth in claim 68 wherein the first
material is platinum.
70. A galvanic probe as set forth in claim 66 wherein the exposed
surface of the reference electrode comprises zinc.
71. A galvanic probe as set forth in claim 70 wherein the exposed
surface of the reference electrode consists essentially of zinc
and, optionally, zinc oxide, zinc hydroxide or both.
72. A galvanic probe as set forth in claim 70 wherein the exposed
surface of the reference electrode comprises zinc of purity in
excess of 99.9% and, optionally, zinc oxide, zinc hydroxide or
both.
73. A galvanic probe as set forth in claim 67 wherein the exposed
surface of the reference electrode comprises zinc.
74. A galvanic probe as set forth in claim 73 wherein the exposed
surface of the reference electrode consists essentially of zinc
and, optionally, zinc oxide, zinc hydroxide or both.
75. A galvanic probe as set forth in claim 73 wherein the exposed
surface of the reference electrode comprises zinc of purity in
excess of 99.9% and, optionally, zinc oxide, zinc hydroxide or
both.
76. A galvanic probe as set forth in claim 68 wherein the exposed
surface of the reference electrode comprises zinc.
77. A galvanic probe as set forth in claim 76 wherein the exposed
surface of the reference electrode consists essentially of zinc
and, optionally, zinc oxide, zinc hydroxide or both.
78. A galvanic probe as set forth in claim 76 wherein the exposed
surface of the reference electrode comprises zinc of purity in
excess of 99.9% and, optionally, zinc oxide, zinc hydroxide or
both.
79. A galvanic probe as set forth in claim 69 wherein the exposed
surface of the reference electrode comprises zinc.
80. A galvanic probe as set forth in claim 79 wherein the exposed
surface of the reference electrode consists essentially of zinc
and, optionally, zinc oxide, zinc hydroxide or both.
81. A galvanic probe as set forth in claim 79 wherein the exposed
surface of the reference electrode comprises zinc of purity in
excess of 99.9% and, optionally, zinc oxide, zinc hydroxide or
both.
Description
BACKGROUND OF THE INVENTION
[0001] (1) Field of the Invention
[0002] The present invention relates to galvanic probes and cells,
and more particularly to the use of such probes and cells in the
measurement of various characteristics, such as pH and oxidation
reduction potential, of fluids such as water.
[0003] (2) Description of the Related Art
[0004] It is often necessary or desirable to measure the pH or
oxidation reduction potential (ORP) of a fluid. The ORP measures
the relative tendency of materials in the fluid to undergo
oxidation or reduction (particularly the ability of the fluid to
destroy bacteria in it). Moreover, it is often desirable to monitor
pH and/or ORP at frequent intervals--or even continuously.
Measurement of pH and ORP levels are of interest in a wide variety
of industrial, commercial and domestic processes and situations.
For example, many chemical processes are pH-dependent or
ORP-dependent. The pH or ORP of effluents from factories is
commonly of environmental concern. The pH or ORP of water is
critical in many settings. A setting familiar to many laypersons is
in various water storage systems, such as air conditioning systems
or swimming pools. Therefore, for ease of explanation, much of the
following discussion will be with reference to the swimming pool
setting, although it should be borne in mind that the discussion is
likewise applicable to any other situation in which the pH and/or
ORP of a fluid is of interest.
[0005] In a swimming pool, the quality of the water is closely
related to the pH and ORP of the water. In swimming pools, the ORP
of the water is a measure of the free chlorine level in the water,
which is related to the biological antiseptic quality of the water.
Therefore, the pH and chlorine levels of swimming pool water must
be monitored to ensure that an adequate quality level is
maintained. Conventionally, this is carried out by hand and the
owner or other caretaker in charge of maintaining the pool must
repeatedly go to the pool with vials and chemicals, scoop out the
water into the vials, shake the vials, compare the colors of the
resulting solutions to those on charts coordinated with the pool
volume to determine the amounts of chemicals to add to restore the
proper pH and/or chlorine level, obtain those chemicals, measure
them out and add them to the pool. Not only is this a cumbersome
process, but if it is not carried out at frequent enough intervals,
the quality of the pool water can become unacceptable very quickly.
Thus, for example, if the pool caretaker is away for a several
days, he or she may return to find a pool filled with murky water.
Or the pH or chlorine level may fall out of acceptable range too
soon before the next testing and the water may become unhealthful,
and the pool caretaker may not realize that fact until it is too
late. Therefore, it is desirable to have a pH monitor and/or an ORP
monitor that would carry out the measurement task automatically and
frequently--even continuously--on a real time basis.
[0006] Unfortunately, however, current technology is ill equipped
for such frequent or continuous monitoring. Conventional pH meters
typically comprise a porous glass membrane enclosing a quantity of
a liquid about a sensing electrode. For example, commercial pH
electrodes typically employ a pair of silver/silver chloride
electrodes, one in a saturated potassium chloride solution, the
other in hydrochloric acid, encased separately in porous glass, and
the pH is determined once the migration of hydrogen ions across the
glass membrane has reached equilibrium. Reaching equilibrium can
require a substantial amount of time. In fact, if the pH of the
fluid being tested changes frequently, such electrodes might never
reach equilibrium and so pH measurement may be impossible without
extraction of a sample and testing the sample, in which case the
measurement is merely historical. Generally, such commercial pH
meters suffer from several other serious drawbacks as well. They
are expensive (typically about US$250), unavailable in large
quantities, require soaker caps to keep the tips wet when not in
use, are affected substantially by temperature, require frequent
recalibration, experience substantial signal drift and, as with all
electrodes that employ liquid fill solutions, must be maintained in
an almost vertical position to keep the electrodes in the tested
fluid. Moreover, because the glass and fill solutions required for
such electrodes, they are fragile, have limited lives, are
incompatible with some industrial processes, especially those in
harsh environments.
[0007] Other pH meters have been noted in the scientific
literature, but are likewise undesirable. Ion selective field
effect transistors (ISFETs), in which the signal is based on a
selective membrane attached to the gate, have been used, but they
also are expensive (about US$300), are unavailable in large
quantities (particularly for commercial applications) and are
highly sensitive to ambient temperature. Potentiometric solid state
sensors, in which measurement is based on ion specific voltage
developed between a reference electrode and a measuring sensor,
have been described in scientific publications, but their
commercialization is extremely limited, and no large-scale
production process has been developed. In any event, they also
suffer from other serious disadvantages. They require frequent
calibration, they suffer from significant drift, they have very
limited lives, have limited applicability because some common salts
damage their sensor membranes, are expensive (although at about
US$20, are less expensive than the previously mentioned meters),
are affected substantially by temperature, and while they can be
stored dry, they require about 24 hours for stabilization.
[0008] Antimony electrodes also have been employed in some pH
sensors, usually in combination with a silver/silver chloride
reference electrode and glass-encased fill solution, with all the
attendant disadvantages of glass membranes and fill solutions noted
above. U.S. Pat. No. 5,497,091 describes a pH sensor that employs
an antimony electrode in combination with a ceramic reference
electrode, but provides no clear description of the ceramic
reference electrode. However, known antimony-based pH sensors
typically employ a polished antimony surface for enhanced
sensitivity and so suffer from deteriorating sensitivity as they
lose polish. In addition, known antimony-based pH sensors typically
also suffer from substantial drift as the quality of the polish
diminishes over time, and, as with the other pH sensors dependent
on ion exchange between the fluid being tested and the fill
solutions, known antimony-based pH sensors frequent recalibration
and limited lifetimes due to gradual dilution of the fill solution.
Moreover, because they employ a liquid fill solution, they must be
maintained in a vertical position. Thus, state of the art pH
monitors are unsuitable for many uses, especially those in which a
durable, inexpensive and readily available (or easy to manufacture)
probe for frequent, accurate, real time pH measurements with low
drift.
[0009] Monitors for measuring ORP also are available commercially.
Their measurements are based on a voltage developed between a
silver/silver chloride reference wire in an internal fill solution
and a platinum wire isolated from the fill solution. Such monitors
also suffer from serious drawbacks, including high cost (about
US$250), unavailability in large quantities, limited life based on
the fill solution, lengthy response time, the requirement of a
soaker cap to keep the tip wet when not in use, and the requirement
of all electrodes that employ fill solutions that that they be
maintained in an almost vertical position to keep the electrodes in
the tested fluid. Thus, as with the state of the art pH monitors,
state of the art ORP probes are unsuitable for many uses,
especially those in which a durable, inexpensive and readily
available (or easy to manufacture) probe for frequent, accurate,
real time ORP measurements with low signal drift.
SUMMARY OF THE INVENTION
[0010] Briefly, therefore, the present invention is directed to a
novel galvanic probe. The probe comprises a sensor electrode and a
reference electrode. The sensor electrode has an exposed surface
that comprises a noble metal or antimony or bismuth, and,
optionally, an oxide or hydroxide thereof. The reference electrode
is spaced apart from the sensor electrode and has an exposed
surface that comprises zinc or magnesium, and, optionally, an oxide
or hydroxide thereof.
[0011] The present invention also is directed to a novel device for
controlling the pH and/or ORP of a fluid in a vessel to a desired
pH and/or ORP level. The device comprises a sensor electrode, a
reference electrode, and a circuit arranged such that the
electrodes generate a signal when the electrodes are in contact
with a fluid such that the electrodes are in electrochemical
communication with each other, and wherein the signal is input to
and processed by said circuit. If the pH is controlled, the sensor
electrode has an exposed surface that comprises antimony or
bismuth, and, optionally, an oxide or hydroxide thereof. If the ORP
is controlled, the sensor electrode has an exposed surface that
comprises a noble metal such as platinum and, optionally, an oxide
or hydroxide thereof. The reference electrode is spaced apart from
the sensor electrode and has an exposed surface that comprises zinc
or magnesium, and, optionally, an oxide or hydroxide thereof.
[0012] The present invention also is directed to a novel method for
measuring the pH and/or ORP of a fluid. According to the method,
electrodes of a probe such as described above are placed into a
fluid and the pH and/or ORP is read from the display.
[0013] The present invention also is directed to a novel galvanic
cell comprising an electrolyte in contact with a sensor electrode
having an exposed surface comprising a noble metal or antimony or
bismuth, and, optionally, an oxide or hydroxide thereof, and a
reference electrode spaced apart from the sensor electrode and
having an exposed surface comprising zinc or magnesium and,
optionally, an oxide or hydroxide thereof.
[0014] Among the several advantages found to be achieved by the
present invention, therefore, may be noted the provision of a novel
pH and/or ORP probe that is durable, inexpensive available probe
for frequent, accurate, real time pH and/or measurements with low
drift; the provision of such probe that is less sensitive to
temperature variations than are conventional probes; the provision
of a novel device for controlling the pH and/or ORP of a fluid in a
vessel, such as (but not limited to) water in a swimming pool, to
desired pH and/or ORP levels; the provision of a novel device for
controlling the pH and/or ORP of a fluid in a vessel, such as (but
not limited to) water in a swimming pool, to desired pH and/or ORP
levels, including a mechanism for adjusting the pH and/or ORP
automatically; and the provision of a novel galvanic cell.
[0015] While the principal advantages and features of the present
have been described above, a more complete and thorough
understanding and appreciation of the invention may be attained by
referring to the drawing figures and description of the preferred
embodiments, which follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic representation of a first embodiment
of a probe of the present invention;
[0017] FIG. 2 is a schematic representation of the signal processor
shown in FIG. 1;
[0018] FIG. 3 is a schematic representation of a second embodiment
of the present invention wherein the probe functions as both a pH
sensor and an ORP sensor;
[0019] FIG. 4 is a schematic representation of a data processor
employed in an embodiment of the probe of the present
invention;
[0020] FIG. 5(a) is a schematic representation of a third
embodiment of a probe of the invention wherein either the pH level
or ORP level of the fluid is sensed, but not both; FIG. 5(b) is a
schematic representation of the third embodiment of a probe of the
invention wherein both the pH level and ORP level of the fluid are
sensed;
[0021] FIG. 6 is a schematic representation of a fourth embodiment
of a probe of the present invention wherein the tasks of the data
processor are distributed between remote components;
[0022] FIG. 7 is a schematic representation of an embodiment of a
probe of the present invention wherein only pH or ORP is sensed by
the electrodes; and
[0023] FIG. 8 is a schematic representation of an embodiment of a
probe of the present invention, similar to that of FIG. 7, but
wherein the electrodes sense both pH and ORP;
[0024] FIG. 9 is a graph of electrode pH response, with the pH as
determined by a commercial pH probe as the ordinate (x coordinate)
and the voltage between the test electrodes and reference electrode
as the abscissa (y coordinate);
[0025] FIG. 10 is a graph of electrode ORP response, with the ORP
as determined by a commercial pH probe and measured in volts as the
ordinate (x coordinate) and the voltage between the test electrode
and the reference electrode as the abscissa (y coordinate);
[0026] FIG. 11 is a graph of electrode pH versus ORP response, with
the ORP as determined by a commercial ORP probe and measured in
volts as the ordinate (x coordinate) and the voltage between the
test electrodes and the reference electrode as the abscissa (y
coordinate);
[0027] FIG. 12 is a graph of electrode pH response versus ORP
response, with the ORP as determined by a commercial ORP probe and
measured in volts as the ordinate (x coordinate) and the pH as
measured by the voltage between the test electrode and the
reference electrode as the abscissa (y coordinate);
[0028] FIG. 13 is a graph of electrode pH response versus
temperature, with the temperature as the ordinate (x coordinate)
and the pH as measured by the voltage between the test electrode
and the reference electrode as the abscissa (y coordinate);
[0029] FIG. 14 is a graph of electrode pH response, with the pH as
determined by a commercial pH probe as the ordinate (x coordinate)
and the pH measured as the voltage between the test electrode and
reference electrode as the abscissa (y coordinate); and
[0030] FIG. 15 is a graph of electrode pH response, with the pH as
determined by a commercial pH probe as the ordinate (x coordinate)
and the pH measured as the voltage between the test electrode and
reference electrode as the abscissa (y coordinate).
[0031] Reference characters in these Figures correspond to
reference figures in the following detailed description of the
preferred embodiments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] In accordance with the present invention, it has been
discovered that, surprisingly, certain combinations of electrode
materials can be used to construct extremely low cost, but long
life and highly durable galvanic probes that can be used to produce
sensors that give highly accurate and quick measurements of certain
characteristics, such as pH and oxidation reduction potential
(ORP), of the electrolytic fluids in which they are placed, while
eliminating the need for delicate and fragile porous glass and
internal fill solutions. The sensors produce highly repeatable and
very stable signals and so often require only a single, simple
initial calibration. The signal has been found to be generally
independent of the sizes of the electrodes and the distance between
them, and that are substantially less affected by temperature
compared to prior art sensors. The signals are directly
proportional to pH or ORP, as the case may be, are high repeatable,
and require only a simple initial calibration. In fact, the sensors
are stable enough to allow for frequent measurements and have such
low drift that they have been found to be capable of providing
frequent, perhaps even continuous, real time measurements of such
fluid characteristics with probe materials costing well under US$1.
The probe does not require either fill solutions or glass
materials. Rather it may be constructed of extremely durable
materials that not only can withstand rough treatment, but also can
be used in a wide variety of systems, including harsh environments.
The probe is not dependent on vertical or any other position
orientation and can be stored dry with a minimum of stabilization
time as compared to prior art sensors. Moreover, because the probe
of this invention employs electrode materials that are galvanic. In
fact, because they generate a current upon contact with an
electrolyte, the probe may be used to produce a galvanic cell.
[0033] The galvanic probe of this invention comprises at least one
sensor electrode in combination with a reference electrode. In
particular, it has been found that an antimony or bismuth sensor
electrode may be used in combination with a zinc or magnesium
reference electrode in the presence of an electrolytic fluid to
produce a signal in the form of a current having a voltage
differential (a potential difference between the electrodes)
directly proportional to the pH of the fluid in the manner to be
discussed in more detail below. Assuming constant resistance,
therefore, the amperage of the current is likewise directly
proportional to the pH of the fluid. Similarly, it has been found
that a noble metal sensor electrode may be used in combination with
a zinc or magnesium reference electrode in the presence of an
electrolytic fluid to produce a signal in the form of a current
having a voltage differential (potential difference between the
electrodes)--and so also an amperage--directly proportional to the
ORP of the fluid in the manner also to be discussed in more detail
below. The antimony or bismuth electrode and the noble metal
electrode are referred to herein as "sensor" electrodes in
distinction to the reference electrode. The electrolyte fluid may
be any nonmetallic fluid, particularly a liquid, that is a
conductor in which electric current is carried by movement of ions
in the fluid. As used herein, the term "conductor" refers to
electrical conductors.
[0034] It is envisioned that the probe of the present invention
would be used typically in aqueous electrolytic liquids. Among such
liquids may be noted water itself and aqueous electrolytic
solutions. An electrolytic fluid of particular interest is swimming
pool water and some of the following discussion will be directed
specifically thereto. However, this discussion should not be viewed
as limiting, as the probe of the present invention has wide-ranging
applications, from measurements of pH and ORP in fluids in chemical
and industrial syntheses, processes and effluents, to such
measurements in streams and lakes. In fact, it is contemplated that
the probes of the present invention can be used to produce sensors
that may be may be used in any system containing an electrolytic
fluid in which it is desired to measure pH or ORP.
[0035] With respect to the antimony or bismuth electrode, antimony
is preferred over bismuth and so the following discussion will
refer to antimony. However, it should be understood that the same
description is applicable to bismuth as well. Thus, the antimony or
bismuth electrode will hereinafter be referred to as "the antimony
electrode," although it will be recognized that, except as noted,
the same explanation will apply for a bismuth electrode, but with
reference to bismuth instead of antimony.
[0036] Although in the most preferred embodiment, it is expected
that the entire antimony electrode will be a piece of solid
antimony material, it is only necessary that at least part of an
exposed surface of the antimony electrode be antimony. As used
herein, an "exposed surface" of an electrode means a surface of the
electrode that comes into direct contact with an electrolytic fluid
when the electrode is placed into the fluid. Thus, other than a
solid piece of antimony, examples of the antimony electrode wherein
at least part of an exposed surface of the electrode is antimony
include a substrate coated with antimony, a substrate with a
portion of its surface coated with antimony, and so forth. Of
course, if a part of the exposed surface of the electrode is a
material other than antimony, it is preferred that the material
other than antimony be inert in the sense that it does not
interfere with the subject electrolytic reaction occurring with the
antimony; that is, perhaps:
2Sb+3H.sub.2OSb.sub.2O.sub.3+6H.sup.++6e.sup.-(2Bi+3H.sub.2OBi.s-
ub.2O.sub.3+6H.sup.++6e.sup.- for bismuth).
[0037] The antimony need not be polished as in certain prior art pH
sensors that employ antimony electrodes. Thus, efficacy of the
antimony electrode has not been found to degrade upon use, despite
the formation of antimony oxide (also called antimony
trioxide--with respect to bismuth, bismuth trioxide or bismuth
tetroxide) or possibly even antimony hydroxide resulting from use
in the probe of this invention. Thus, it is contemplated that the
exposed surfaces of the antimony electrode may also bear such
oxides or hydroxides, particularly once used.
[0038] Similarly to the antimony electrode, at least part of an
exposed surface of the noble metal electrode is a noble metal.
Preferably, the noble metal is platinum, gold or silver, most
preferably platinum. Thus, the noble metal electrode may be any
solid electrode wherein at least part of an exposed surface of the
electrode is a noble metal. Preferably, the electrode is a solid
piece of the noble metal, but it need not be. For example, other
than a solid piece of the noble metal, the noble metal electrode
may be a substrate coated with the noble metal, a substrate with a
portion of its surface coated with the noble metal, and so forth.
Of course, if a part of the exposed surface of the electrode is a
material other than the noble metal, it is preferred that the
material other than the noble metal be inert in the sense that it
does not interfere with the subject electrolytic reaction with the
noble metal; that is, for example, in the case of platinum,
perhaps:
Pt+H.sub.2OPtOH+H.sup.++e.sup.-
PtOHHOPt (rearrangement)
HOPtOpt+H.sup.++e.sup.-
[0039] Also as with the antimony electrode, the platinum need not
be polished. Thus, efficacy of the noble metal electrode has not
been found to degrade upon use, despite the formation of oxides or
hydroxides of the noble metal resulting from use in the probe of
this invention. Thus, it is contemplated that the exposed surfaces
of the noble metal electrode may also bear such oxides or
hydroxides, particularly once used.
[0040] At least part of an exposed surface of the reference
electrode is zinc or magnesium. Although the reference electrode
may be either zinc or magnesium, the present inventors have found
less drift in readings when the reference electrode is zinc than
when it is magnesium, and so zinc is preferred. The reference
electrode may be any solid electrode wherein at least part of an
exposed surface of the electrode is zinc or magnesium. Preferably,
the electrode is a solid piece of zinc or magnesium, but it need
not be. For example, the reference electrode may be a solid piece
of zinc or magnesium, a substrate coated with zinc or magnesium
(e.g., galvanized sheet metal), a substrate with a portion of its
surface coated with zinc or magnesium, and so forth. Of course, if
a part of the exposed surface of the electrode is a material other
than zinc or magnesium, it is preferred that the material other
than zinc or magnesium be inert in the sense that it does not
interfere with the subject electrolytic reaction with the zinc or
magnesium; that is, for example: ZnO+2H.sup.++2e.sup.-Zn+H.sub.2O
or MgO+2H.sup.++2e.sup.-Mg+H.sub.2O. However, it has been found
that the efficacy of the electrode is greatly--and
deleteriously--affected by the presence of other impurities, such
as trace amounts of tin, lead and copper. This is typically not a
problem with most fluids, including tap water such as may be found
in pools and spas and the like. However, the deleterious impurities
need not arise from the fluid itself. They might also derive from
the electrodes. In fact, it has been found that the sensitivity of
the probe of the present invention decreases significantly if the
reference electrode incorporates zinc of lower purity than about
99.99%, and especially lower than about 99.9%, is greatly
preferred. Accordingly, it is preferred that the reference
electrode comprise zinc of purity at least about 99.9%, especially
at least about 99.99%.
[0041] When discussing purity, it will be appreciated that the
electrolytic process may cause the materials of the electrodes to
oxidize and so some of the material may be present in oxidized
form. As with the sensor electrodes, efficacy of the reference
electrode has not been found to degrade upon use, despite the
formation of oxides or hydroxides of the zinc or magnesium
resulting from use in the probe of this invention and the zinc or
magnesium need not be polished and it is contemplated that the
exposed surfaces of the reference electrode may also bear such
oxides or hydroxides, particularly once used. In fact, the
electrolytic process results in increases and decreases in the
proportion of the reference electrode that is in the reduced state.
versus oxidized state (and inversely corresponding increases and
decreases in the proportion of the sensor electrode(s) that in the
reduced state versus oxidized state) as the pH or ORP level
changes. In the context of the present application, therefore, the
fact that some of the material may be in oxidized form is not
viewed as indicating a lower the purity of the material. Thus, in
calculating purity values, the oxidized form of the material should
be considered as part of the pure material component and associated
anions, e.g., oxide or hydroxide, should be discounted.
[0042] In general, the quality of the signal produced by the
electrodes when in operation in a galvanic probe of this invention
is independent of the sizes and shapes of the electrodes, at least
within the reasonable limits of typical electrode sizes. However,
by way of illustration, it has been found that a practical size for
a flat, rectangular zinc reference electrode is at least about 0.25
inches wide.times.0.375 inches long.times.0.031 inches thick, and
for a flat, round zinc reference electrode is at least about 0.375
inches in diameter.times.0.125 inches thick. Platinum sensor
electrodes in the form of a wire 0.005 inches thick.times.0.5
inches long have been found to yield high quality results as
well.
[0043] A probe of this invention comprises one or both types of the
sensor electrodes described above in combination with the reference
electrode described above. Although both types of sensor electrodes
may be used at the same time with a single reference electrode or
with a separate reference electrode designated for each type of
sensor electrode, there is generally no advantage to use of
separate reference electrodes, particularly when measurements
associated with both types of sensor electrodes are to be taken in
proximity to each other. Thus, although references herein to "the"
or "a" reference electrode in the systems employing both types of
sensor electrodes are intended to encompass situations wherein a
plurality of reference electrodes are employed, a probe with a
single reference electrode is the preferred embodiment.
[0044] The probe is a galvanic probe, and may be used as a galvanic
cell as well as a probe. Thus, when the electrodes of a probe of
this invention are an electrolytic fluid is contacted with the
probe such that the sensor electrode(s) and reference electrode of
the probe are in electrochemical communication and the reference
electrode and sensor electrode(s) are further interconnected with
an electric circuit, a current of electricity is generated and
flows through the circuit from the reference electrode to the
sensor electrode. By "electrochemical communication," what is meant
is that the electrolytic fluid is in contact with both the sensor
electrode(s) and the reference electrode such that ions may move
therebetween.
[0045] In an especially desirable form, the electrodes are mounted
on a substrate. This not only provides a convenient way to handle
and to use the electrodes as a single unit, but also maintains the
distance(s) between the electrodes. The electrodes, of course,
should be spaced apart from one another (measurements of the
characteristics of the fluid are dependent on the employment of the
fluid as an electrolyte between the electrodes), but the electrodes
need not be far apart. In fact, it is preferred that the sensor
electrode (or each sensor electrode if more than one is employed)
be relatively close to the reference electrode--say, as close as 1
mm--to avoid significant fluid flow between the electrodes
continually changing or deleteriously affecting the
measurements.
[0046] The substrate may be any other material that does not
interfere with the electrolytic process. Thus, the substrate should
not be or comprise, for example, a conductor, such as metal, or an
ionic compound soluble in the electrolytic fluid (of course the
substrate should be insoluble in the fluid, even if nonionic), but
may be plastic (e.g., acrylic), ceramic, wood, and so forth.
Preferably, the substrate is solid and sturdy. The electrodes may
be affixed to the substrate in any manner, including gluing,
cementing, friction-fitting, not metallic banding, etc. Of course,
preferably the material used in affixing the electrodes to the
substrate likewise is not of the type that interferes with the
electrolytic process.
[0047] The probe may comprise the reference electrode and the
antimony or bismuth sensor electrode, the reference electrode and
the noble metal sensor electrode or the reference electrode(s) and
both types of sensor electrodes. A probe consisting of the
reference electrode and the antimony or bismuth electrode has been
found to provide an excellent pH sensor, as will be discussed
further below. A probe consisting of the reference electrode and
the noble metal electrode has been found to provide an excellent
ORP sensor, as will be discussed further below. A probe comprising
all three types of electrodes has been found to provide an
excellent sensor of both pH and ORP. If the probe includes all
three types of electrodes it is preferred that the reference
electrode be a single electrode positioned between the two types of
sensor electrodes.
[0048] FIG. 1 depicts a preferred embodiment of the invention
wherein the probe functions as either a pH sensor or an ORP sensor.
The probe comprises a sensor electrode 10 and a reference electrode
12, which may be mounted on a substrate 14 as discussed above. If
the sensor electrode 10 is an antimony or bismuth electrode, the
probe may be used as a pH sensor. If the sensor electrode 10 is a
noble metal electrode, the probe may be used as an ORP sensor.
[0049] When the electrodes 10 and 12 are placed in the electrolytic
fluid 16, the electrodes initiate electrochemical communication
with each other and a voltage differential V.sub.IN develops
between the sensor electrode 10 and reference electrode 12.
Therefore, a galvanic cell is created and when a circuit between
the electrodes is completed, the electrodes, in interaction with
the fluid, generate a current galvanically and the current flows to
and through a circuit from the reference electrode to the sensor
electrode. The circuit is represented schematically in FIG. 1 by
the signal processor 18 and the conductive inputs 19a and 19b
extending between the electrodes and the signal processor 18. The
current therefore provides an input to a circuit represented
schematically in FIG. 1 as the signal processor 18. The input may
be processed by the signal processor 18 with respect to any of the
characteristics of that current or information communicated by that
current, such as voltage or amperage of the current. For the sake
of simplicity, the voltage differential is identified in FIG. 1 as
V.sub.IN, however, any current characteristic or information may be
the input processed by signal processor 18 as desired for the
particular processing of interest.
[0050] A more detailed schematic representation of the signal
processor 18 is shown in FIG. 2. As illustrated in FIG. 2, the
signal processor 18 may comprise an amplifier 20, if so desired.
For example, the amplifier may be set to a X1 gain and serve as a
buffer or set to, for example, a X9 gain to reduce the input range
or to enlarge the output range in an op-amp type circuit to amplify
the signal prior to the detection device. If an amplifier 20 is
used, the inputs 19a and 19b are directed to the amplifier 20. The
output signal S.sub.O of the amplifier 20 then is routed to an
information processor 22. If the amplifier 20 is omitted, the
inputs 19a and 19b are routed directly to the information processor
22, in that case S.sub.O represents the inputs 19a and 19b.
[0051] The information processor 22 may processes the signal
S.sub.O in any of a multitude of ways. Thus, the information
processor 22 may be but is not necessarily a microprocessor. In
fact, the information processor 22 may be any item that is
activated by, responds to, operates on or measures some
characteristic of an electric current. For example, information
processor 22 may be a light bulb, an alarm, a electro-activated
switch or any other such devices or combination of devices that
operate on an electrical current.
[0052] Preferably, however, the information processor 22 is a
detection device for detecting a characteristic of the current or
information communicated by the current, most preferably in
combination with a processor, such as a microprocessor to translate
the current or information to another form (a numerical value, a
reading on a gauge, a new signal, etc.). In one embodiment, the
information processor 22 may be a voltmeter, in which case, the
current characteristic would be the voltage differential V.sub.IN
(which may be expressed, for example, in millivolts) between the
electrodes, or an ammeter, in which case the characteristic would
be the amperage of the current I.sub.IN (which may be expressed,
for example in milliamperes). In another embodiment, the
information processor measures the voltage or amperage of the
current and translates that information to a signal indicative of
pH or ORP. Because the current generated by the probe is relatively
small, the information processor 22 should have a low impedance.
However, in a preferred embodiment, the device detects or measures
voltage.
[0053] When the probe is a pH sensor, the sensor electrode 10
exchanges hydrogen ions with the fluid 16. This exchange of ions
can be measured as the amperage of the current I.sub.IN flowing
through the circuit or the voltage differential V.sub.IN between
the electrodes and is reflective of the pH level of the fluid 16.
Surprisingly, it has been found that the amperage of the current
I.sub.IN and the voltage V.sub.IN are both linearly related to the
pH. In other words, a graph of the current amperage I.sub.IN or the
voltage V.sub.IN versus the pH of the fluid on Cartesian
coordinates is a straight line. Thus, the pH may be derived from
the current I.sub.IN or the voltage V.sub.IN may be derived from
the simple equations AI.sub.IN+B or AV.sub.IN+B, respectively,
wherein A is a constant corresponding to the slope of the line and
B is a constant corresponding to the translation (shifting) of the
line from the origin.
[0054] When the probe is an ORP sensor, the resultant voltage
differential V.sub.IN, which develops as oxidation and reduction
occurs in the fluid 16, is reflective of the ORP level of the fluid
16. Similarly, it also has been found, again surprisingly, that the
amperage of the current I.sub.IN and the voltage V.sub.IN are both
linearly proportional (subject to translation) to the ORP. In other
words, a graph of the amperage of the current I.sub.IN or the
voltage V.sub.IN versus the ORP of the fluid on Cartesian
coordinates is a straight line. Thus, the ORP may be derived from
the current I.sub.IN or the voltage V.sub.IN may be derived from
the simple equations AI.sub.IN+B or AV.sub.IN+B, respectively,
wherein A is a constant corresponding to the slope of the line and
B is a constant corresponding to the translation (shifting) of the
line from the origin.
[0055] In a preferred embodiment in which the probe is a pH or ORP
sensor, the basic function of the information processor 22 is to
determine from the input signal S.sub.O what the actual pH level or
ORP level of the fluid 16 is. The information processor 22
translates the signal S.sub.O to translated information directly
indicative of the pH or ORP, respectively, of the fluid contacted
by the electrodes according to the noted equations.
[0056] Because the voltage differential and amperage are linearly
related to the pH and ORP, calibration is simple. A reading
indicative of voltage differential or amperage of just two samples
of known pH or ORP defines the line expressing the linear
relationship and thus determines A and B in the noted
equations.
[0057] Once the translated information directly indicative of the
pH level or ORP level is determined by the information processor
22, such data can be supplied to a display unit 24, which is
configured to display the determined pH level or ORP level to a
user. Preferably, the display unit can be an LCD interfaced with
the information processor 22. However, it is easily understood by
one of ordinary skill in the art that the display unit can be
virtually any device that can communicate the pH level or ORP level
in a meaningful way to a user, including but not limited to a
needle and gauge calibrated to translate the information processor
output to a pH level of ORP level or an LED display configured to
identify the pH/ORP level.
[0058] Also, it must be noted that the task of designing the exact
circuitry used by the information processor 22 to process the
sensed data signal S.sub.O is well within the routine knowledge of
one of ordinary skill in the electronic arts following the
teachings of the invention. The inventor herein envisions that a
vast number of data processing circuits of widely varying
complexity can be developed for effectively determining the pH
level or ORP level from the sensed data signal S.sub.O. For
example, as noted above, the data processor 18 can be as simple as
a voltmeter connected to the electrode outputs (upon reading the
voltage from the voltmeter, a user could consult a chart depicting
pH/ORP levels as a function of voltage), or can be as complex as
logic array specifically designed to determine the pH/ORP level
from the sensed data signal S.sub.O.
[0059] FIG. 3 depicts a second embodiment of the invention wherein
the probe functions as both a pH sensor and an ORP sensor. In this
embodiment, the substrate 26 includes three electrodes: a first
sensor electrode 28 for sensing the pH level of fluid 34, a
reference electrode 30, and a second sensor electrode 32 for the
ORP of fluid 34. For simplicity in the following discussion, the
first sensor electrode 28 will be denoted as a pH sensor while the
second sensor electrode 32 will be denoted as an ORP sensor.
Preferably, the reference electrode 30 is positioned between the
first and second sensor electrodes 28 and 32.
[0060] In this embodiment, the voltage differential V.sub.IN1 that
develops between the first sensor electrode 28 and the reference
electrode 30 will be reflective of the pH level of the surrounding
fluid 34 and will be supplied to a first data processor 36. The
voltage differential V.sub.IN2 that develops between the second
sensor electrode 32 and the reference electrode 30 will be
reflective of the ORP level of the surrounding fluid 34 and will be
supplied to a second data processor 38. The first and second data
processors 36 and 38 can be collectively referred to as data
processor 40. The first data processor 36 can be implemented as
described above in connection with FIGS. 1 and 2 except that it
will be specifically focused on determining the pH level from the
data signal V.sub.IN1. The second data processor 38 can also be
implemented as described above in connection with FIGS. 1 and 2
except that it will be specifically focused on determining the ORP
level from the data signal V.sub.IN2. Also, as would be apparent to
those of ordinary skill in the art, the tasks of the first and
second data processors 36 and 38 can be implemented using the same
microprocessor, wherein such a microprocessor is configured to
separately receive and process both V.sub.IN1 and V.sub.IN2.
[0061] FIG. 4 shows a preferred data processor 40 wherein a first
amplifier 42 is used to amplify V.sub.IN1 and a microprocessor 44
receives the amplification of V.sub.IN1 via a first input 46. A
second amplifier 48 is used to amplify V.sub.IN2, and the
microprocessor 44 receives the amplification of V.sub.IN2 via a
second input 50. The microprocessor 44 can be configured to
separately process the pH data signal received via first input 46
and the ORP data signal received via second input 50. As discussed
above, the microprocessor 44 can be configured in a variety of ways
to determine the pH level and ORP level from the sensed data
signals. Once the pH and ORP levels are determined, a display unit
52 interfaced with the microprocessor can display those levels.
[0062] In more sophisticated versions of the first and second
embodiments of the invention, the data processor 18 of FIG. 1 and
the data processor 40 of FIG. 4 can be configured to determine from
the pH level or ORP level how much of a treatment chemical is
needed to alter the pH level or ORP level of the fluid to a
suitable value. Thus, instead of or in addition to the translated
information indicative of pH and/or ORP as determined by the
information processor being directed to a display that displays the
pH or ORP, it may be directed to a display indicating the amount of
treatment chemical should be added to alter the pH or ORP level, or
even to a mechanism for adding such amount, as will be discussed in
more detail below.
[0063] For example, when the probe is used in connection with
swimming pools, the user could quickly learn how much of a chemical
must be added to the pool by simply inserting the electrodes in the
pool water and reading from the display unit how much treatment
chemicals need to be added. Alternatively, the electrodes can
remain submerged perpetually in the pool water, providing
continuous data, intermittent data or data upon command such as by
activating a switch. In the case of a swimming pool, the ORP
reading may be desirable in the form of the chlorine level of the
water. To implement this design, it is preferable that an input
device 54 be interfaced with a microprocessor (which may be the
information processor) so that a user can inform the microprocessor
of certain information such as the desired pH level and/or chlorine
level of the pool water, the volume of the pool being analyzed.
This input device can be any known device for inputting data from a
keypad to a touchscreen to a voice recognition device. Of course,
the pool volume could be prestored in the microprocessor.
[0064] The probe of the present invention is substantially less
temperature dependent than are some prior art probes and, depending
on the application, the probe may be used with or without
temperature compensation. If a probe of the present invention is to
include compensation for the temperature of the fluid, an
additional input may be the temperature of the water of the fluid
being tested. Accordingly, a temperature-sensing device, such as a
thermometer 25, may provide an input of information indicative of
the temperature of the fluid. The apparent pH/ORP levels may then
be corrected to true pH/ORP levels, for example, by resort to
reference tables prepared from tests conducted at various
temperatures on fluid samples of known pH/ORP or from mathematical
relationships determined from such tests.
[0065] Again, for illustrative purposes, attention is directed to
swimming pools. Once the microprocessor knows the pH/ORP level of
the pool, the volume of the pool and, optionally the temperature of
the pool water, the microprocessor can be configured to determine
how much treatment chemical is needed to bring the pool back to an
acceptable pH/ORP level. For example, a lookup table referencing
chemical amounts by pool volume and pH/ORP levels can be stored in
microprocessor memory and accessed once the pool volume is entered
via input device 54 and the pH/ORP level has been determined.
Alternatively, the microprocessor can be configured to calculate
the amount of chemical from predetermined formulas.
[0066] Also, in a third embodiment of the present invention, shown
in FIGS. 5(a) and 5(b), the probe can be implemented such that the
sensing functions and data processing functions are performed
separately from each other. FIG. 5(a) shows the third embodiment of
the invention wherein either the pH level or ORP level of the fluid
is sensed, but not both (the electrode assembly 56 includes only a
single sensor electrode 10). FIG. 5(b) shows the third embodiment
of the invention wherein both the pH level and ORP level of the
fluid are sensed (the electrode assembly 58 includes both a first
sensor electrode 28 and a second sensor electrode 32). In FIG. 5(a)
a data transmission unit 60 is interfaced with the electrode
assembly 56. The data transmission unit 60 receives the sensed data
signal V.sub.IN, converts V.sub.IN to an output signal
V.sub.TRANSMIT, and transmits V.sub.TRANSMIT to a remote data
receiving unit 62. In FIG. 5(b) a data transmission unit 64 is
interfaced with the electrode assembly 58. The data transmission
unit 64 receives the sensed data signals V.sub.IN1 and V.sub.IN2,
converts V.sub.IN1 and V.sub.IN2 to output signals V.sub.TRANSMIT1
and V.sub.TRANSMIT2, and transmits V.sub.TRANSMIT1 and
V.sub.TRANSMIT2 to a remote data receiving unit 66. The data
receiving units 62 and 66 of FIGS. 5(a) and (b) are then interfaced
with data processors 18 and 40 respectively. The data receiving
units convert the signal received from the data transmission units
to a format appropriate for the data processors 18 and 40. Of
course such data transmission can occur at any of a number of
points in the information processing process, so that a
characteristic of or information from the current from the
electrodes can be transmitted, with the bulk of processing carried
out at the receiving end, or the bulk of the processing can be
carried out prior to transmission.
[0067] The data transmission units 60 and 64 can be coupled to the
data receiving units 62 and 66 via any known technique of wireless
communication between remote locations, for example RF
communication, infrared (IR) communication, etc. A wide spectrum of
available techniques for transmitting data between spatially
separated locations, the exact technique used to transmit the
sensed data signal(s) to the remote data processor will be readily
apparent to those of ordinary skill in the electronic arts. In one
preferred embodiment, the data transmission units may be encased in
a small housing (with electrodes exposed) that may be adapted to
float freely in a pool.
[0068] FIG. 6 shows a fourth embodiment of the present invention
wherein the tasks of the data processor are distributed between
remote components. The output from microprocessor 68 (which can be
signal reflective of the pH level, ORP level, or amount of
treatment chemical needed) can be interfaced with a data
transmission unit 70 as described above. A remote display unit 72
can be interfaced with a data-receiving unit 74 as described above.
As explained above, the data transmission unit and data receiving
unit can be coupled using any known technique of wireless
communication between remote locations.
[0069] FIGS. 7 and 8 depict a fifth embodiment of the invention,
wherein chemicals are automatically added to the probed fluid in
response to the sensed and measured pH or ORP level. FIG. 7 depicts
the invention wherein only pH or ORP is sensed by the electrodes 10
and 12. FIG. 8 depicts the invention wherein both pH and ORP are
sensed by the electrodes 28, 30, and 32.
[0070] In FIG. 7, an automatic dispensing unit 76 is interfaced
with the data processor 18. The automatic dispensing unit will have
stored therein a given amount of chemical(s) needed to change
either the pH level or ORP level of the fluid 16 to a desired
level. In response to instructions from the data processor 18, the
automatic dispensing unit will be configured to dispense an
appropriate amount of the stored chemical(s) such that the fluid
will achieve a desired pH or ORP level. Because the appropriate
amount of chemical(s) needed to be added to the fluid 16 will vary
as a function of the volume of the fluid 16, the data processor
will need data identifying the fluid's volume. As explained above,
the data processor 18 may include an input device interfaced to a
microprocessor that allows a user to enter the fluid's volume
(i.e., the volume of the user's pool). Alternatively, this pool
volume can be pre-stored in the microprocessor. The data processor
18 will need to translate the sensed data signal V.sub.IN,
translate that signal to a pH level or ORP level, and then
translate the determined pH/ORP level to an amount of chemical(s)
that needs to be dispensed into the fluid 16 (this amount will be a
function of the fluid's volume). Of course, the data processor 18
can be configured to skip the step of determining the pH/ORP level
and translate the data signal V.sub.IN directly to an amount of
chemical(s) needed to make the appropriate pH or ORP adjustment in
the fluid.
[0071] In FIG. 8, the configuration of components is very similar
to that of FIG. 7 except that both the pH level and ORP level are
being sensed, and therefore the automatic dispensing unit will need
to be configured to dispense the chemicals needed to make
appropriate adjustments to both the pH level and ORP level of the
fluid 34. Because the exact design of automatic dispensing units 76
and 78, wherein a measured amount of stored chemical(s) is (are)
controllably dispensed in response to an input signal, is well
within the common knowledge of a person of ordinary skill in the
electronic and mechanical arts, the inventor herein envisions that
a wide variety of automatic dispensing units can be developed in
accordance with the teachings of this invention, and will leave
such routine designs to those ordinarily-skilled artisans.
[0072] The data processors 18 and 40 in the embodiments of FIGS. 7
and 8 can also include other devices to convey information relating
to the pH/ORP, such as a display unit for displaying the pH/ORP as
discussed above and/or an alarm programmed to activate when the
pH/ORP moves outside a pre-set range.
[0073] It is also contemplated that in some forms, the electrodes
may generate enough current to run the data processor, rendering
the unit self-powering. Alternatively, the data processor,
displays, alarms, dispensers or other may be power by solar energy,
batteries or wall current, etc.
[0074] The following examples describe preferred embodiments of the
invention. Other embodiments with the scope of the claims herein
will be apparent to one skilled in the art from consideration of
the specification or practice of the invention as disclosed herein.
It is intended that the specification, together with the examples,
be considered exemplary only, with the scope and spirit of the
invention being indicated by the claims which follow the
examples.
EXAMPLE 1
[0075] A beaker (250 ml) was filled with cold tap water and placed
on a hot plate/stirrer. A magnetic stir bar was added into the
beaker and a calibrated commercial pH, ORP and temperature sensor
were inserted into the beaker along with antimony, platinum and
99.99% pure zinc electrodes of the present invention. The
electrodes were suspended high enough in the beaker so as not to
interfere with the magnetic stirrer. The pH, ORP and temperature of
the water were measured and recorded with both the commercial and
the electrodes of the present invention. The tap water tested
typically has a pH of about 9.5, an ORP of about +200 mV and
temperature of about 71.degree. F. The initial pH was adjusted
incrementally downward in several tests by addition of a
proportional amount (about 5 mg) of an acidic chemical such as
sodium bisulfate or muriatic Acid (referred to as pH-down
chemical). After each addition of chemical the stirrer was run
briefly at about 60 rpm until the solid chemical was dissolved. The
pH is allowed to stabilize at various levels and the signal values
of each sensor were recorded. In each of the tests, when the water
pH was less than 5, the pH was adjusted incrementally upward by
adding a proportional amount (about 5 mg) of an alkaline chemical
such as soda ash or sodium bicarbonate (referred to as pH-up
chemical). After each addition of chemical, the stirrer was run
briefly at about 60 rpm until the solid chemical was dissolved. The
pH was allowed to stabilize at various levels and the signal values
of each sensor were recorded. The pH was adjusted upward until it
reached about 9.5. The measured values of pH signals were then are
plotted with the pH values indicated by the calibrated commercial
probe on the horizontal (X) axis and the signal values from the
commercial ORP electrode (identified as "ORP Standard"), the pH
electrode of the present invention (identified as "Antimony pH
Electrode"), and ORP electrode (identified as "Platinum ORP
Electrode) on the vertical (Y) axis. This plot is shown in the
graph of FIG. 9. This graph show that when very little oxidation or
reduction is taking place (here, ORP is about 0.200 V), both the
commercial ORP electrode and the platinum ORP electrode of this
invention exhibit a pH dependence. FIG. 10 shows the ORP signals
plotted with the signals from the commercial ORP electrode
(identified as "Commercial ORP Electrode Response") on the
horizontal (X) axis and the signals from the ORP electrode of the
present invention (identified as "DCI Platinum ORP Response") on
the vertical (Y) axis. According to the graph of FIG. 10, the
commercial ORP electrode shows a pH dependence similar to that of
the ORP electrode of this invention. FIG. 11 shows the commercial
ORP electrode response (identified as "Commercial ORP Reading")
plotted on the horizontal (X) axis and the commercial pH electrode
signal (identified as "Commercial pH Electrode raw sig") and the
signal of the antimony pH electrode of the present invention
(identified as "Antimony pH Electrode") plotted on the vertical (Y)
axis. The graph of FIG. 11 shows that the commercial electrode
exhibits an ORP dependence similar to that of the antimony pH
electrode of the present invention.
EXAMPLE 2
[0076] A beaker (250 ml) was filled with cold tap water and placed
on a hot plate/stirrer. A magnetic stir bar was added into the
beaker and a calibrated commercial pH, ORP and temperature sensor
were inserted into the beaker along with antimony, platinum and
99.99% pure zinc electrodes of the present invention. The
electrodes were suspended high enough in the beaker so as not to
interfere with the magnetic stirrer. The pH, ORP and temperature of
the water were measured and recorded with both the commercial and
the electrodes of the present invention. The tap water tested
typically has a pH of about 9.5, an ORP of about +200 mV and
temperature of about 71.degree. F. This test was carried out after
the pH exposure of Example 1, above, and the commercial ORP
electrode took some time to return back to the original value that
it had before the pH test. For each test, the initial pH was
adjusted incrementally downward to about pH 7 by adding a
proportional amount (about 2 mg) of an acidic chemical such as
sodium bisulfate or muriatic Acid (pH-down). After each addition of
chemical the stirrer was run briefly at about 60 rpm until the
solid chemical dissolved. The pH was allowed to stabilize and then
the signal values of each sensor were recorded. After the pH
stabilized at around 7, a proportional amount (about 4 mg) of
buffer salt (sodium hydrogen carbonate) was added to make the pH
more stable. After each addition of chemical, the stirrer was run
briefly at about 60 rpm until the solid chemical dissolved. At
times, it was noted that the pH rose slightly after the buffer salt
was added, and when that occurred, trace amounts of pH-down were
added to bring the pH back to about 7. The amount of pH-down
necessary to effect a decrease similar to that achieved in the
first adjustment downward to pH 7 was higher than that required in
the first adjustment downward higher since the solution had been
buffered to resist small changes in the pH. When the pH was stable,
a proportional amount of (about 2 mg) of a chlorinating compound
(trichloro-s-triazinetr- ione) was added. The ORP was allowed to
stabilize and the signal values of each sensor were recorded. After
the initial reading from the previous step, the ORP was
incrementally raised by adding trace amounts of chlorinating
compound, letting the signal stabilize, and then recording the
signal values. The amount of chlorinating compound required for
this small beaker was extremely small and it is very easy to
overdose. For the amount of chemical involved, the response time
may be considerable. The signals were then plotted with the ORP
values as indicated by the commercial probe on the horizontal (X)
axis and the signal values from the pH and ORP sensors (identified
as "Antimony" and "platinum wire", respectively) on the vertical
(Y) axis. This plot is shown in the graph of FIG. 12. This graph
shows that at a constant pH level, the antimony pH sensor was
relatively independent of the ORP reading.
EXAMPLE 3
[0077] A beaker (250 ml) was filled with cold tap water and placed
on a hot plate/stirrer. A calibrated commercial pH, ORP and
temperature sensor were inserted into the beaker along with a
calibrated temperature probe and antimony, platinum and 99.99% pure
zinc electrodes of the present invention. The electrodes were
suspended high enough in the beaker so as not to touch the bottom
of the beaker. The pH, ORP and temperature of the water were
measured and recorded with both the commercial sensors and the
electrodes of the present invention. The tap water tested typically
has a pH of about 9.5, an ORP of about +200 mV and temperature of
about 71.degree. F. The Hot Plate was turned on to its lowest
setting; i.e., #1. As the temperature rose, the signal on each
sensor and the current temperature were recorded. The temperature
then was plotted on the horizontal (X) axis and the signals from
the other electrodes on the vertical (Y) axis. This plot is shown
in the graph of FIG. 13 and illustrates that the temperature
response of the antimony electrode is linear, with a slope of about
-1.5 mV/.degree. F.
EXAMPLE 4
[0078] By a method as described in Example 1, above, voltage
readings were taken from the antimony electrode at various pH's as
determined by the commercial pH sensor. The results were plotted on
the graph shown in FIG. 14. The method was repeated with a
magnesium reference electrode in place of the zinc electrode. The
results were plotted on the graph shown in FIG. 15. It can be seen
from FIGS. 14 and 15 that the voltage in both cases is linearly
related to the pH. In each case, R.sup.2 has been calculated and
shown to be very close to 1, establishing the relationship to
linear to be extremely close. The formulae for the lines in each
case have been determined, showing the relationship between the pH
(x) and the voltage (y).
[0079] All references, including without limitation all papers,
publications, presentations, texts, reports, manuscripts,
brochures, internet postings, journal articles, periodicals, and
the like, cited in this specification are hereby incorporated by
reference. The discussion of the references herein is intended
merely to summarize the assertions made by their authors and no
admission is made that any reference constitutes prior art. The
inventors reserve the right to challenge the accuracy and
pertinence of the cited references.
[0080] In view of the above, it will be seen that the several
advantages of the invention are achieved and other advantageous
results obtained: As various changes could be made in the above
methods and compositions without departing from the scope of the
invention, it is intended that all matter contained in the above
description as shown in the accompanying drawings shall be
interpreted as illustrative and not in a limiting sense.
* * * * *