Abstract:
There is provided a refrigerant system. First and second transducers are positioned within the refrigerant system to measure respective operational characteristics. There is 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 after that specified time and determines whether the outputs of the first and second transducers are within a tolerance band of each other. If the readings are not within tolerance band, then the transducer failure is detected and a warning/alarm requiring operator attention is issued.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to detecting transducer failures. More particularly, the present invention relates to detecting transducer failure in refrigerant systems. 
         [0003]    2. Description of the Related Art 
         [0004]    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&#39;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. 
         [0005]    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. 
         [0006]    Detecting a transducer failure, however, can be a time consuming and an effort intensive process. For example, in some test scenarios, each transducer is tested separately for a plurality of known operating conditions, and the output of each transducer is then compared against manufacturer&#39;s specifications to determine if the transducer is working properly. 
         [0007]    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 
       [0008]    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. 
         [0009]    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. 
         [0010]    It is an object of the present application to detect transducer failure with less cost and time-consumption. 
         [0011]    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 
         [0012]      FIG. 1  illustrates a controller according to the present invention for a refrigerant system that tests transducers for failure. 
           [0013]      FIG. 2  is a method according to the present invention for testing transducers for failure in a refrigerant system. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0014]      FIG. 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 . 
         [0015]    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 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. 
         [0016]    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&#39;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). 
         [0017]    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. 
         [0018]    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 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&#39;s tolerance specification. If they are not identical within a manufacture&#39;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. 
         [0019]    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&#39;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. 
         [0020]    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. 
         [0021]    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  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). 
         [0022]    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. 
         [0023]    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. 
         [0024]    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  (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. 
         [0025]    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 fans  162  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. 
         [0026]    It is understood that the schematics shown in  FIG. 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 . 
         [0027]      FIG. 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. 
         [0028]    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 . 
         [0029]    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&#39;s specifications for tolerances for first and second transducers  150 ,  160  are also loaded into comparator  180 . Method  200  proceeds to step  225 . 
         [0030]    In step  225 , method  200  conveys manufacturer&#39;s tolerances for both first and second transducers  150 ,  160  to comparator  180 . Method  200  proceeds to step  230 . 
         [0031]    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 . 
         [0032]    In step  240 , timer  175  waits for the period of time specified in step  210 . Method  200  proceeds to step  250 . 
         [0033]    In step  250 , comparator  180  reads the outputs of first and second transducers  150  and  160 . Method  200  proceeds to step  260 . 
         [0034]    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 . 
         [0035]    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. 
         [0036]    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 . 
         [0037]    In step  280 , the user replaces either first transducer  150 , second transducer  160 , or both. Method  200  then stops. 
         [0038]    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.