U.S. patent application number 12/083797 was filed with the patent office on 2009-10-15 for diagnostic method for proper refrigerant valve operation.
Invention is credited to Boris Karpman, Alexander Lifson, Michael F. Taras.
Application Number | 20090255281 12/083797 |
Document ID | / |
Family ID | 37962795 |
Filed Date | 2009-10-15 |
United States Patent
Application |
20090255281 |
Kind Code |
A1 |
Lifson; Alexander ; et
al. |
October 15, 2009 |
Diagnostic Method for Proper Refrigerant Valve Operation
Abstract
There is provided a refrigerant system 100 including at least
one or a plurality of refrigerant flow control devices 125 for
regulating operational parameters of the refrigerant system 100, at
least one sensor 135, 140 connected to the refrigerant system 100
for monitoring the operational parameters of the refrigerant system
100, and a controller 130. The controller 130, which is connected
to the plurality of refrigerant flow control devices 125 and to
each of the at least one sensor 135, 140, switches a refrigerant
flow control device 125 of the plurality of refrigerant flow
control devices 125 between a first operating state and a second
operating state, separately observes a variation in an operational
parameter resulting from the switching of each refrigerant flow
control device 125 of the plurality of refrigerant flow control
devices 125, compares the observed variation with an expected
variation due to the switching, and determines whether the
refrigerant flow control device 125 is operating properly based on
whether the actual variation corresponds to the expected variation.
There is also provided a method for diagnostic testing of the
refrigerant system 100.
Inventors: |
Lifson; Alexander; (Manlius,
NY) ; Taras; Michael F.; (Fayetteville, NY) ;
Karpman; Boris; (Marlborough, CT) |
Correspondence
Address: |
OHLANDT, GREELEY, RUGGIERO & PERLE, LLP
ONE LANDMARK SQUARE, 10TH FLOOR
STAMFORD
CT
06901
US
|
Family ID: |
37962795 |
Appl. No.: |
12/083797 |
Filed: |
October 18, 2005 |
PCT Filed: |
October 18, 2005 |
PCT NO: |
PCT/US05/37671 |
371 Date: |
April 18, 2008 |
Current U.S.
Class: |
62/129 ; 62/115;
62/190 |
Current CPC
Class: |
F25B 2500/19 20130101;
F25B 2700/1931 20130101; F25B 2700/21152 20130101; F25B 2700/1933
20130101; F25B 49/005 20130101; G05B 23/0256 20130101 |
Class at
Publication: |
62/129 ; 62/190;
62/115 |
International
Class: |
F25B 1/00 20060101
F25B001/00 |
Claims
1. A method for diagnostic testing of a refrigerant system 100
having at least one refrigerant flow control device 125,
comprising: switching said at least one refrigerant flow control
device 125 from a first operating state to a second operating
state, in response to a diagnostic request from a controller 130;
observing a variation in at least one operational parameter of at
least a portion of said refrigerant system 100 resulting from said
switching of said at least one refrigerant flow control device 125;
and comparing said observed variation with an expected variation
due to said switching.
2. The method of claim 1, further comprising determining whether
said refrigerant flow control device 125 is operating properly
based on whether said observed variation corresponds to said
expected variation within a predefined tolerance range.
3. The method of claim 1, wherein said refrigerant flow control
device 125 is a valve 125, wherein said first operating state is a
first position of said valve 125, and said first operating state is
selected from the group consisting of: completely open, completely
closed, and partially closed, and wherein said second operating
state is a second position of said valve 125, and said second
operating state is selected from the group consisting of:
completely open, completely closed, and partially closed.
4. The method of claim 1, wherein said operational parameter is
selected from a group consisting of temperature, pressure and
electric current.
5. The method of claim 1, wherein said system has a plurality of
refrigerant flow control devices 125, and wherein said method is
performed individually and sequentially on each of at least two
selected refrigerant flow control devices 125 of said plurality of
refrigerant flow control devices 125, and wherein during said steps
of switching each said refrigerant flow control device 125 and
observing said variation, an operating state of untested
refrigerant flow control devices 125 of said plurality of
refrigerant flow control devices 125, which have a potential effect
on said operational parameter, is unaltered.
6. The method of claim 1, wherein said refrigerant flow control
device 125 is determined to be operating properly if said observed
variation is substantially equal to said expected variation, and
wherein said refrigerant flow control device 125 is determined to
be malfunctioning if said observed variation is substantially
different from said expected variation.
7. The method of claim 1, wherein said observed variation and said
expected variation is selected from the group consisting of: a
change between a first parameter corresponding to said first
operating state and a second parameter corresponding to said second
operating state, and a rate of change in said first parameter.
8. The method of claim 1, further comprising a step selected from
the group consisting of: returning said at least one refrigerant
flow control device 125 to said first operating state after
observing said variation, and allowing said at least one
refrigerant flow control device 125 to remain in said second
operating state after observing said variation.
9. The method of claim 1, wherein said at least one refrigerant
flow control device 125 has more than two operating states, and
wherein said method is performed multiple times by switching said
at least one refrigerant flow control device 125 to a plurality of
operating states, and performing said steps of observing and
comparing for each of said plurality of operating states.
10. The method of claim 1, wherein said variation is observed
repeatedly over a selected period of time, and changes in said
variation are observed to record and analyze degradation of said at
least one refrigerant flow control device 125.
11. A refrigerant system 100, comprising: at least one refrigerant
flow control device 125 for regulating operational parameters of
said refrigerant system 100; at least one sensor 135, 140 connected
to said refrigerant system 100 for monitoring said operational
parameters of said refrigerant system 100; a controller 130,
connected to said at least one refrigerant flow control device 125
and to each of said at least one sensor 135, 140, that switches a
refrigerant flow control device 125 between a first operating state
and a second operating state, observes a variation in at least one
operational parameter resulting from said switching of said at
least one refrigerant flow control device 125, and compares said
observed variation with an expected variation due to said
switching.
12. The system of claim 11, wherein said controller 30 determines
whether said refrigerant flow control device 125 is operating
properly based on whether said observed variation corresponds to
said expected variation within a specified tolerance range.
13. The system of claim 11, wherein said operational parameter is
selected from a group consisting of temperature, pressure, and
electric current, and wherein said sensor 135, 140 is selected from
the group consisting of a pressure sensor 135, a temperature sensor
140, and an electric current sensor.
14. The system of claim 11, wherein said refrigerant flow control
device 125 is a valve 125, and wherein said first operating state
is a first position of said valve 125, and said second operating
state is a second position of said valve 125.
15. The system of claim 11, further comprising an interface 155
connected to said controller for providing information related to
said observed variation and said expected variation, and for
receiving input related to said expected variation and from
refrigerant flow control devices 125 to be tested.
16. The system of claim 11, wherein said controller 130 determines
that said refrigerant flow control device 125 is operating properly
if said observed variation is substantially equal to said expected
variation, and wherein said controller 130 determines that said
refrigerant flow control device 125 is malfunctioning if said
observed variation is substantially different from said expected
variation.
17. The system of claim 11, wherein said refrigerant system 100 has
a plurality of refrigerant flow control devices 125, wherein said
controller is connected to said plurality of refrigerant flow
control devices 125, and wherein said controller switches at least
one refrigerant flow control device 125 of said plurality of
refrigerant flow control devices 125 between a first operating
state and a second operating state and separately observes a
variation in at least one operational parameter resulting from said
switching of each said refrigerant flow control device 125.
18. The system of claim 17, wherein said controller 130 performs at
least the switching and separately observing steps individually and
sequentially on each of at least two selected refrigerant flow
control devices 125 of said plurality of refrigerant flow control
devices 125, and wherein during said switching and observing steps,
an operating state of untested refrigerant flow control devices 125
of said plurality of refrigerant flow control devices 125, which
have a potential effect on said operational parameter, is
unaltered.
19. The system of claim 11, wherein said refrigerant system 100 is
selected from the group consisting of a single-circuit system and a
multi-circuit system.
20. A system or method for diagnostic testing of at least one
refrigerant flow control device 125 of a plurality of refrigerant
flow control devices 125 of a refrigerant system 100 as herein
before described with reference to any one of FIGS. 1, 2, 3 and 4
of the accompanying drawings.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to diagnostic systems and
methods, and more particularly, to diagnostic systems and methods
in refrigerant systems.
[0003] 2. Description of the Related Art
[0004] Typically, in complex refrigerant systems, it is difficult
to diagnose a malfunctioning system component. Additionally, if the
problem is not identified in a timely manner, the malfunctioning or
broken component can cause substantial secondary damage to other
components in the system. There are numerous examples of adjustable
flow control devices, e.g., valves, within a refrigerant system
that can potentially malfunction, such as a compressor unloading
valve and a pressure regulating valve. Vapor (or liquid) injection
valve failure is a typical example as well. If the vapor injection
valve failure is not detected within a reasonable period of time,
i.e., hours, it can often result in compressor damage, since with
the malfunctioning vapor injection valve the compressor may operate
at substantially higher then designed discharge temperatures.
Similarly, a malfunctioning suction modulation valve may cause
abnormally low saturation suction temperatures and refrigerant flow
rates resulting in potential problems concerning oil return to the
compressor and proper lubrication of internal compressor
components.
[0005] There is a need for a simple diagnostic/prognostic method
that will allow for a timely detection of such failures, thus
preventing prolonged downtime and costly repairs of the
equipment.
SUMMARY OF THE INVENTION
[0006] There is provided a refrigerant system including at least
one refrigerant flow control device or a plurality of refrigerant
flow control devices for regulating operational parameters of the
refrigerant system, at least one sensor connected to the
refrigerant system for monitoring operational parameters of the
refrigerant system, and a refrigerant system controller. The
controller, which is connected to the refrigerant flow control
devices and to each of the at least one sensor, separately and
selectively switches each refrigerant flow control device between a
first operating state and a second operating state, separately
observes a variation in at least one operational parameter
resulting from the switching of each refrigerant flow control
device, and compares the observed variation with an expected
variation due to the switching. The system controller determines
whether the refrigerant flow control device is operating properly
based on whether the actual variation corresponds to the expected
variation within a predefined tolerance range.
[0007] In one embodiment, the refrigerant system has a plurality of
refrigerant flow control devices. The controller is connected to
the plurality of refrigerant flow control devices, and the
controller switches at least one refrigerant flow control device of
the plurality of refrigerant flow control devices between a first
operating state and a second operating state and separately
observes a variation in at least one operational parameter
resulting from the switching of each refrigerant flow control
device.
[0008] There is also provided a method for diagnostic testing of a
refrigerant system having at least one regulating refrigerant flow
control device. The method includes individually switching at least
one refrigerant flow control device from a first operating state to
a second operating state, in response to a diagnostic request from
a controller, and separately observing a variation in at least one
operational parameter of at least a portion of the refrigerant
system resulting from the switching of each refrigerant flow
control device. The method also includes comparing the observed
variation with an expected variation due to the switching, and
determining whether the refrigerant flow control device is
operating properly based on whether said observed variation
corresponds to expected variation within a predefined tolerance
range.
[0009] In one embodiment of the method, the refrigerant system has
a plurality of refrigerant flow control devices. The method is
performed individually and sequentially on each of at least two
selected refrigerant flow control devices of the plurality of
refrigerant flow control devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a diagram of an exemplary refrigerant system
including a diagnostic system according to the present
invention.
[0011] FIG. 2 is a graph showing changes in operational parameters
in response to turning a refrigerant flow control device on or
off.
[0012] FIG. 3 is a graph showing changes in pressure in response to
turning a refrigerant flow control device on or off.
[0013] FIG. 4 is a graph showing changes in pressure in response to
changes in the operational states of one or more refrigerant flow
control devices.
DESCRIPTION OF THE INVENTION
[0014] FIG. 1 shows a refrigerant system 100 including a diagnostic
system 105 according to the present invention. Refrigerant system
100 includes refrigerant lines 110 connecting system components,
condenser and evaporator heat exchangers 115 cooperating with
corresponding fans 150, expansion devices 120, compressor 145,
economizer heat exchanger 117, and a plurality of refrigerant flow
control devices 125 for regulating operational parameters of
refrigerant system 100. In one embodiment, refrigerant flow control
devices 125 are valves. Refrigerant system 100 may be a
single-circuit system or a multi-circuit system. The schematic
presented in FIG. 1 is purely exemplary; there are many possible
configurations and variations of the design of refrigerant system
100 that are not shown but fall within the scope of the
invention.
[0015] Diagnostic system 105 includes a controller 130, pressure
sensors 135, and temperature sensors 140. Also, additional electric
current sensors may be included. Sensors 135 and 140 are connected
at various points to refrigerant system 100, and, for simplicity
purposes, are preferably connected to lines 110. Sensors 135 and
140 assist in monitoring operational parameters, such as
temperature and pressure, of refrigerant system 100 by transmitting
electric signals indicative of temperature and/or pressure to
controller 130.
[0016] Controller 130 is connected to refrigerant flow control
devices 125 and sensors 135 and 140. Controller 130 can switch
refrigerant flow control devices 125 between at least two operating
states, such as "on", i.e., a completely open position, or "off",
i.e., a completely closed position. The operating state of
refrigerant flow control devices 125 may also be an intermediate
position, i.e., partially open or closed, or a plurality of such
intermediate positions (for example, if a refrigerant flow control
device is equipped with a stepper motor). A first operating state
is associated with a first position of refrigerant flow control
device 125, and a second operating state is associated with a
second position of refrigerant flow control devices 125.
[0017] Controller 130 receives electric signals from sensors 135
and 140, translates these signals into operational parameter
information, and compares received operational parameter
information with expected operational parameters. Controller 130
also separately observes a variation in at least one operational
parameter in at least a portion of refrigerant system 100 resulting
from switching of each refrigerant flow control device 125,
compares this variation with an expected variation due to the
switching, and determines whether each refrigerant flow control
device 125 is operating properly based on whether the actual
variation corresponds to the expected variation within a predefined
tolerance range.
[0018] Controller 130 may switch refrigerant flow control devices
125 into an "on" or "off" position, or move refrigerant flow
control device 125 to an intermediate position (if the refrigerant
flow control device is equipped with such capability), in response
to received parameter information, and may control the operation of
other components of refrigerant system 100, such as compressor 145.
Such actions performed by controller 130 may be required to prevent
malfunctioning and permanent damage to components of refrigerant
system 100. Also, controller 130 may provide information to a user,
such as expected and observed parameters, and, based on this
information, whether a refrigerant flow control device is in proper
working order or whether there is a malfunction.
[0019] Controller 130 determines that a refrigerant flow control
device 125 is operating properly if the observed variation is
substantially equal to the expected variation. Likewise, controller
130 determines that refrigerant flow control device 125 is
malfunctioning if the observed variation is substantially different
from the expected variation. In one embodiment, a tolerance value,
or minimum difference between the observed variation and the
expected variation can be predetermined, so that any difference
greater than the tolerance value will trigger a malfunction
determination.
[0020] In another embodiment, when more than one refrigerant flow
control device 125 is selected to be tested, controller 130
performs at least the switching and separately observing steps
individually and sequentially on each of the at least two
refrigerant flow control devices 125 to be tested. Each refrigerant
flow control device 125 is individually tested/diagnosed, one at a
time. During testing/diagnosis of each refrigerant flow control
device 125, the operating states of other refrigerant flow control
devices and other components that may have an effect on the
operational parameter are unaltered. In this way, the effect on the
operational parameter, if any, is known to be from the refrigerant
flow control device 125 that is under test. In another embodiment,
after a test of one refrigerant flow control device is completed,
that refrigerant flow control device is typically returned to its
normal operating state before a subsequent refrigerant flow control
device is tested.
[0021] Controller 130 preferably includes a computing platform,
such as a personal computer, a mainframe computer, or any other
type of computing platform that may be provisioned with a memory
device (not shown), a CPU or microprocessor device (not shown), and
several I/O ports (not shown). Controller 130 may also include a
display or other device for providing information, and a visual or
audio indicator to indicate a malfunctioning component. Refrigerant
system 100 may also include an interface 155 connected to
controller 130 for providing information related to the observed
variation and the expected variation, and for receiving input
related to the expected variation and to a selection of components
to be tested. The interface may also allow a user to set component
parameters and to directly control components of refrigerant system
100 and/or diagnostic system 105.
[0022] There is provided a method for diagnostic testing of
refrigerant system 100 having a plurality of refrigerant flow
control devices 125. The method includes switching at least one
refrigerant flow control device 125 from a first operating state to
a second operating state, in response to a diagnostic request from
controller 130. A variation in at least one operational parameter,
such as temperature or pressure, of at least a portion of
refrigerant system 100 is observed as a result of the switching of
each refrigerant flow control device 125. The observed variation of
the at least one operational parameter is compared via controller
130 with an expected variation. Based on the difference between the
observed variation and the expected variation, it is determined,
preferably by controller 130, whether refrigerant flow control
device 125 is operating properly. In another embodiment, the method
includes an initial step of observing at least one operational
parameter of at least a portion of refrigerant system 100 to
generate the expected variation.
[0023] Refrigerant flow control device 125 is determined to be
operating properly if the observed variation is substantially equal
to the expected variation. Likewise, refrigerant flow control
device 125 is determined to be malfunctioning if the observed
variation is substantially different from the expected variation.
For example, if refrigerant flow control device 125 is broken, no
change in operation occurs. If refrigerant flow control device 125
is functioning properly, then there is a step change in the
corresponding operational parameter as would be expected. If there
were a partial malfunction, a change or variation in the
corresponding operational parameter would be observed but would be
different than the expected change of this operational
parameter.
[0024] For example, when pressure sensor 135, for measuring
compressor suction or compressor discharge pressure, is installed
on line 110 associated with suction port or discharge port of
compressor 145 respectively, a change in refrigerant flow control
device 125 operating state would be expected to cause a step change
in pressure. If such step change is not present, refrigerant flow
control device 125 malfunction is detected. A piston or plunger of
refrigerant flow control device 125 can, for example, be stock or
"frozen in place" due to debris present that prevents its proper
movement. Likewise, a temperature step change can be detected.
[0025] A graph illustrated in FIG. 2, having a y-axis showing both
a temperature value, "T.sub.DISCHARGE", a pressure value,
"P.sub.DISCHARGE", and an x-axis indicating time, "t", reveals a
change in at lease one operating parameter in response to a
corresponding refrigerant flow control device being moved or
switched from one operating state to another. For instance, if a
vapor (or liquid) injection valve is shut down, i.e., closed, the
discharge temperature, shown in a solid line, should be expected to
increase by a certain amount above the measurement tolerance
threshold. If such a change is not observed, as shown by the dotted
line in FIG. 2, the vapor (or liquid) injection valve is not
operating properly and is thus not delivering enough vapor and/or
liquid to cool compressor 145. Analogously, if a compressor
unloading valve is closed prior to the system shutdown, a discharge
pressure increase will indicate proper operation of the compressor
unloading valve. The vapor injection valve and compressor unloading
valve are exemplary. The graph of FIG. 2 demonstrates similar
effects in other types of refrigerant flow control devices. As is
shown in FIG. 2, both properly operated valves are moved to their
original states at the end of the test.
[0026] Similarly, for example, partially closing a suction
modulation valve should be expected to cause a suction pressure to
decline. If such decline does not occur, the suction modulation
valve is not functioning properly. This is shown in FIG. 3, having
a y-axis representing decreasing suction pressure value,
"P.sub.SUCTION" corresponding to partial suction modulation valve
closure, and an x-axis representing time, "t". As shown in FIG. 3,
if the suction modulation valve is at least partially closed, the
suction pressure shown in a solid line is expected to decrease. The
observed P.sub.SUCTION, shown by a dotted line, represents a
malfunctioning suction modulation valve. Similarly, as shown in
FIG. 3, properly operating suction modulation valve is returned to
its original position after the test is complete.
[0027] Similar relationships can be established for many other
refrigerant flow control devices, including but not limited to
discharge valves, economizer valves, pressure regulating valves,
etc. FIGS. 2 and 3 demonstrate an instance where a refrigerant flow
control device is completely malfunctioning or entirely lost its
control. In other instances, a refrigerant flow control device may
be only partially malfunctioning, and thus a change in pressure or
temperature may be observed. However, such change in temperature or
pressure will not be equivalent or substantially equivalent to the
expected change.
[0028] FIG. 4 demonstrates additional embodiments, and includes a
y-axis representing stepwise increasing pressure value, "P", and an
x-axis representing time, "t". One embodiment includes a
refrigerant flow control device having a stepper-motor that changes
position of the refrigerant flow control device in a step pattern.
Proper operation of the refrigerant flow control device produces
pressure values corresponding to the solid line in FIG. 4, and
representing proper operation based on pre-programmed values. The
dotted line shows an example of a malfunctioning refrigerant flow
control device and/or stepper-motor, illustrating step values that
are different than expected step values.
[0029] FIG. 4 also demonstrates an additional embodiment of the
method. In previous embodiments, each refrigerant flow control
device, e.g. valve, is returned to its original operating position
prior to testing of a next refrigerant flow control device. In the
embodiment represented in FIG. 4, each refrigerant flow control
device is not returned to its original operating position, but is
left in an operating position, e.g., the second operating state, at
which corresponding system operational parameters were observed
last. Each sequentially tested refrigerant flow control device
produces another step in the at least one corresponding operational
parameter, e.g., pressure value. In the present example, each valve
is, for instance, closed for a test, and remains closed as
subsequent valves are tested. The solid line shows proper step
increases in pressure value corresponding to the shutdown of each
valve. The dotted line represents at least one malfunctioning
valve, as the dotted line does not correspond to the expected
values as shown in the solid line. The refrigerant flow control
devices, i.e., valves in one embodiment, under consideration and
testing should be associated with the same at least one operational
parameter.
[0030] In the instance where at least two refrigerant flow control
devices 125 in refrigerant system 100 are tested, controller 130
performs the method on each designated refrigerant flow control
device, one at a time, i.e., individually and sequentially, to
verify the refrigerant flow control device's proper operation.
During the test of each refrigerant flow control device, the
operating states of all of the untested components and/or
refrigerant flow control devices, particularly those that would
have a potential effect on the at least one operational parameter
under consideration, are unaltered so that the individual effect on
the operational parameters of refrigerant system 100 by each
refrigerant flow control device can be detected. For example,
during a pre-shutdown diagnostic procedure, controller 130 steps
through the method wherein each refrigerant flow control device
under consideration is moved from an initial to a final operating
state, and the change in at least one of the corresponding
operational parameters is observed.
[0031] The frequency and sequence of such diagnostics for each
refrigerant flow control device may be based on confidence in
refrigerant flow control device reliability or criticality of its
functionality for the operation of refrigerant system 100. For
example, refrigerant flow control devices that have a lower
reliability may be tested more frequently than more reliable
refrigerant flow control devices. In one embodiment, under
practical circumstances, the method can be performed once per
day.
[0032] In another embodiment, in addition to the observed and
expected variation values being simple differences or step values,
the expected and observed variation may be a rate of change, i.e. a
derivative, of the observed variation and a rate of change of the
expected variation. Observing the rate of change would allow larger
magnitudes of the system characteristics under observation to be
registered, thus permitting detection of a malfunctioning
refrigerant flow control device sooner.
[0033] The method may be performed on refrigerant system 100, or on
each circuit of a multi-circuit system. The method may be performed
just prior to, i.e., very shortly before system shutdown. The
method may also be performed during normal operation of refrigerant
system 100. In this embodiment, controller 130 issues a signal to
change the position of refrigerant flow control device 125, the
test of the function of refrigerant flow control device 125 is
performed as described above, then refrigerant flow control device
125 is returned back to a position for normal operation of
refrigerant system 100.
[0034] In another embodiment, at least one refrigerant flow control
device 125 has more than two operating states, such as open,
closed, and one or more various partially open states. In this
embodiment, the method may be performed multiple times by switching
the at least one refrigerant flow control device 125 to a plurality
of operating states, and performing the steps of observing and
comparing actual and expected changes in at least one corresponding
operational parameter for each of the plurality of operating
states.
[0035] Although this method is the most beneficial in the field,
i.e., during normal use of refrigerant system 100, the method can
also be successfully employed at the factory, when refrigerant
system 100 is undergoing final run tests. Lastly, if performance
degradation of some critical refrigerant flow control devices is
monitored and recorded over a period of time, the method can form a
basis for a prognostic toolbox, in which the changes in variation
of at least one operational parameter corresponding to a particular
refrigerant flow control device are compared overtime or with
certain periodicity. Variation may be observed repeatedly over a
selected period of time, and changes in the variation are observed
to record and analyze degradation of at least one refrigerant flow
control device. This will allow preventive maintenance of
refrigerant system 100 and avoidance of undesired prolonged
shutdown intervals.
[0036] One advantage of the system and method of the present
invention is that it would not require any additional expenditures
on any additional components, as the diagnostic-method can be
accomplished simply through appropriate software changes.
[0037] It should be understood that various alternatives,
combinations and modifications of the teachings described herein
could be devised by those skilled in the art. The present invention
is intended to embrace all such alternatives, modifications and
variances that fall within the scope of the appended claims.
* * * * *