Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR DETECTING
TRANSDUCER FAILURE IN REFRIGERANT SYSTEMS
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to detecting transducer failures. More
particularly, the present invention relates to detecting transducer failure in
refrigerant systems.
2. Description of the Related Art
[0002] Refrigerant systems typically have multiple installed pressure and
temperature transducers. These transducers are used to measure pressure and
temperature characteristics in various locations within the refrigerant
systems.
The outputs of these transducers are then used to control operation of the
refrigerant system, as well as to verify that the refrigerant system is
operating
within manufacturer's specifications. Furthermore, these transducer outputs
are
used to adjust operating parameters and to change modes of operation of the
refrigerant system in response to varying environmental conditions.
[0003] However, due to such factors as improper handling practices, exposure
to
harsh environments, manufacturing defects, inappropriate installations
techniques,
wear and tear, and so forth, these transducers may be damaged, and therefore
fail
to function properly. This damage results in a transducer malfunction, or
otherwise readings that noticeably deviate from factory specification. This,
in
turn, will cause system malfunctioning, since refrigerant system controllers
relying
on faulty transducer readings will have a faulty feedback.
[0004] Detecting a transducer failure, however, can be a time consuming and an
effort intensive process. For example, in some test scenarios, each transducer
is
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tested separately for a plurality of known operating conditions, and the
output of
each transducer is then compared against manufacturer's specifications to
determine if the transducer is working properly.
[0005] Therefore, there is a need for a system and a method to verify proper
operation and test transducers in a refrigerant system that addresses at least
some
of the concerns associated with conventional refrigerant transducer
technology.
SUMMARY OF THE INVENTION
[0006] In one embodiment, there is provided a refrigerant system. A first
transducer and second transducer are provided for measuring a characteristic
associated with a first component and a second component of the refrigerant
system. A compressor is connected to the first and second components. A
controller is connected to the first and second transducers. The controller
has a
timer that determines that a shutdown has occurred for a specified period of
time;
and a comparator that compares an output of the first transducer to an output
of
the second transducer and determines whether the outputs of the first and
second
transducers are within a desired tolerance band of each other.
[0007] In another embodiment, there is provided a method for detecting
transducer failure. A compressor is shut down. Then, a specified time period
is
elapsed. A first output of a first transducer connected to a first component
is
measured. A second output of a second transducer connected to a second
component is measured. The first output and said second output are compared to
determine whether the first and second outputs are within a desired tolerance
of
one another. In yet another aspect, the first and second outputs are compared
by
utilizing conversion equations or correlations when different transducer types
are
used.
[0008] It is an object of the present application to detect transducer failure
with
less cost and time-consumption.
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[0009] It is a further object of the present invention to timely detect
transducer
failure to prevent system malfunction and potential failure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates a controller according to the present invention for
a
refrigerant system that tests transducers for failure.
[0011] FIG. 2 is a method according to the present invention for testing
transducers for failure in a refrigerant system.
DESCRIPTION OF THE INVENTION
[0012] FIGURE 1 illustrates a refrigerant system ("system") generally
represented
by reference numeral 100 that has a first transducer 150 and a second
transducer
160. System 100 also incorporates a first refrigerant system component (or
component) 110, such as, for example, a condenser, a second refrigerant system
component (or component) 120, such as, for example an evaporator, an expansion
device 130, a compressor 140, a controller 165, and a data storage media 185.
[0013] An output of first transducer 150 is connected to a first input of
controller
165. An output of second transducer 160 is connected to a second input of
controller 165. An output of the first transducer 150, associated with the
component 110, is connected to a controller 165. Similarly, an output of the
second transducer 160, associated with the component 120, is also connected to
the controller 165. A first transducer 150 is located on the high-pressure
side of
the compressor 140 and refrigerant system 100. A second transducer 160 is
located on the low-pressure side of compressor 140 and refrigerant system 100.
First transducer 150 and second transducer 160 are pressure transducers.
Controller 165 may be connected to storage media 185. Controller 165 has a
shutdown logic 170, a timer 175, and a comparator 180. In one further
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embodiment, controller 165 is also connected to a human-machine interface(s),
such as a keyboard/mouse 187 for input, and a monitor screen 190 for output.
[0014] Generally, shutdown logic 170 shuts down compressor 140 that, while in
operation, circulates refrigerant through refrigerant system 100. Then, timer
175
clocks a given amount of time, and then sends a start signal to comparator
180.
Comparator 180 compares an output of first transducer 150 and an output of
second transducer 160 to determine whether the obtained output readings are
within a manufacture's specification of one another. In one embodiment,
storage
media 185 has computer instructions for accomplishing the above, specific
values
for the given amount of time that timer 175 is to wait, and the manufacturers
specifications for first and second transducers 150 and 160 (i.e., what the
various
electrical output characteristics of the transducers should be at various
pressures,
and so on).
[0015] In system 100, first transducer 150 is located on the high-pressure
side of
compressor 140, and second transducer 160 is located on a low-pressure side of
compressor 140. In one embodiment, both first transducer 150 and second
transducer 160 are pressure transducers. In another embodiment, first
refrigerant
system component 110 is an evaporator, and second refrigerant system component
120 is a condenser. First and second transducers 150 and 160 can be associated
with any other components of the refrigerant system 100 located on high and
low-
pressure sides.
[0016] If compressor 140 is operating, then first transducer 150 and second
transducer 160 will measure disparate pressures or other characteristics under
steady state or normal system 100 operation. During shutdown sequence of
system 100, controller 165, through shutdown logic 170, shuts down compressor
140, so compressor 140 is no longer operating. Timer 175 then waits a
specified
period of time to elapse and then issues a signal to comparator 180. The
waiting
period is used to equalize, as much as practical, the pressures measured by
first
transducer 150 and second transducer 160. In one embodiment, the specified
time
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period for waiting is one minute (60 seconds) but could be as long as a few
minutes, such as 3 minutes (180 seconds). Comparator 180 then compares an
output of first transducer 150 and second transducer 160 to one another to see
if
the outputs are identical, within the manufacturer's tolerance specification.
If they
are not identical within a manufacture's tolerance of one another, then at
least one
of first transducer 150 or second transducer 160 needs to be replaced.
Therefore, a
warning signal is sent to monitor 190 that informs an operator that an error
condition has been detected in either first transducer 150 or second
transducer 160
or otherwise alerts and alarms the operator that a fault condition has been
detected.
[0017] Determining the difference between the outputs of two transducers, such
as
first transducer 150 and second transducer 160, and comparing this difference
to a
manufacture's tolerance specification by comparator 180, as opposed to testing
first transducer 150 and second transducer 160 against their respective pre-
defined
transducer characteristics, will save troubleshooting time and effort as well
as unit
downtime. This determination can be performed in a number of situations, such
as either in the field or in a factory during assembly.
[0018] Furthermore, more than two transducers can be used in system 100. For
instance, the output of a third transducer (not illustrated) could also be
compared
against the output of first transducer 150 if the third transducer is located
on the
low-pressure side of compressor 140. Also, the output of the third transducer
could also be compared against the output of second transducer 160 if the
third
transducer is located on the high-pressure side of compressor 140. Also,
transducers positioned on the same side of the refrigerant system 100 but in
different locations, for instance for redundancy, can be compared one against
the
other.
[0019] In a further embodiment, a plurality of transducers 150 may be
connected
to high-pressure side of system 100 (e.g. connected to component 110), and a
plurality of transducers 160 may be connected to lower-pressure side of the
system
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100 (e.g. connected to component 120). With the plurality of transducers 150
and
160 one transducer can be, for instance, a pressure transducer 152, and a
second
transducer can be a temperature transducer 162. Alternatively, there can be
two
transducers of the same type (i.e., both transducers are pressure or
temperature
transducers).
[0020] In a further embodiment, a plurality of shutdowns occur over a
relatively
long period of time. In other words, shutdown logic 170 issues a plurality of
shutdown commands over such a period of time. Then, after timer 175 and
comparison logic 180 have both performed their respective functions, any trend
in
the measured deviation between first transducer 150 and second transducer 160
can be used as a diagnostics tool. Furthermore, the frequency of first and
second
transducer 150, 160 testing can vary as a function of the confidence in the
reliability of transducers 150 and 160, their criticality to system
functionality and
particular application.
[0021] Although for purposes of the above discussion, first and second
transducers 150 and 160 are described as pressure transducers, other types of
transducers, such as temperature transducers, can also be used. However, it is
noted that typically it takes a longer period of time for temperatures within
system
100 to substantially equalize as compared to pressure transducers. Also, some
precaution measures are to be taken if temperature transducers are utilized,
since,
under some circumstances, temperatures within system 100 could differ from one
.location to the other, which may cause first transducer 150 or second
transducer
160 to provide false readings. In one embodiment, controller 165 or storage
media 185 would have adjustments entered to account for such an offset.
[0022] In a still further embodiment, first transducer 150 is a pressure
transducer
and second transducer 160 is a temperature transducer. Once system 100 is
stabilized and it is believed that temperatures or pressures are equalized, an
output
of first transducer 150 and second transducer 160 are compared to each other.
However, the correlation between first transducer 150 and second transducer
160
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(i.e., that so many measured units of temperature characteristic equals so
many
measured units of pressure characteristic) is typically programmed into
controller
170 or storage media 185 ahead of time.
[0023] In a yet still further embodiment, comparator 180 operation can be
initiated
as part of system 100 startup logic, where first transducer 150 and second
transducer 160 outputs are compared with each other just prior to starting
compressor 140 and starting fans162 and 164. In this case, the time for
pressure
and temperature parameters to equalize is therefore effectively extended to
the
maximum time interval between compressor 140 shutdown and startup.
[0024] It is understood that the schematics shown in FIGURE 1 does not cover a
vast majority of potential system 100 configurations, but is exemplary of one
preferred embodiment. As shown, compressor 140 is connected to various
elements in system 100, either directly or indirectly through other elements
in
system 100. In the context of this disclosure, evaporator and condenser are
defined
broadly to include all associated piping that connects the main body of the
evaporator or condenser to the compressor or to the associated expansion
devices.
Thus, in one embodiment, transducers 150 and 160 can be placed at any location
in the system including the piping associated with an evaporator, condenser or
compressor, or other elements, such as expansion device 130.
[0025] FIGURE 2 illustrates a method 200 for detecting a failure of first and
second transducers 150 and 160. Generally, method 200 compares the output of
first and second transducers 150 and 160 to each other to determine if the
outputs
are identical, within manufactures specification (i.e., that they are
substantially
identical), or otherwise the outputs bear some acceptable mathematical
relationship to one another. If the comparison reveals that the relationship
is
violated, then it is determined that at least one of first and second
transducers 150
and 160 needs to be replaced.
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[0026] In step 210, the specified time that timer 175 waits after shutdown
before
issuing a signal to comparator 180 is determined or otherwise discovered by
controller 165. Method 200 proceeds to step 220.
[0027] In step 220, the mathematical relationship between first transducer 150
and
second transducer 160 is determined and loaded into comparator 180. This can
be
a 1:1 ratio in the case of substantially identical transducers, or some other
relationship, such as when first transducer 150 is a pressure transducer, and
second transducer 160 is a temperature transducer. Furthermore, manufacturer's
specifications for tolerances for first and second transducers 150, 160 are
also
loaded into comparator 180. Method 200 proceeds to step 225.
[0028] In step 225, method 200 conveys manufacturer's tolerances for both
first
and second transducers 150, 160 to comparator 180. Method 200 proceeds to step
230.
[0029] In step 230, shutdown logic 170 shuts down compressor 140 and other
components associated with refrigerant system 100. Method 200 then advances to
step 240.
[0030] In step 240, timer 175 waits for the period of time specified in step
210.
Method 200 proceeds to step 250.
[0031] In step 250, comparator 180 reads the outputs of first and second
transducers 150 and 160. Method 200 proceeds to step 260.
[0032] In step 260, comparator 180 compares the outputs of first and second
transducers 150 and 160 to see if the outputs of first and second transducers
150
and 160 are identical within the tolerances specified in step 225. If they
are, then
method 200 proceeds to step 265. If they are not, method 200 proceeds to step
260.
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[0033] In step 265, neither the first or second transducers 150 and 160 are
replaced, as an error condition has not been detected. Method 200 then stops.
[0034] In step 270, either first transducer 150, second transducer 160, or
both, are
not operating within manufacturing parameters. Therefore, the user is alerted
via
console 190.
[0035] In step 280, the user replaces either first transducer 150, second
transducer
160, or both. Method 200 then stops.
[0036] 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.
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