CA2033860A1 - Diagnostic interpretation of connected sensors - Google Patents
Diagnostic interpretation of connected sensorsInfo
- Publication number
- CA2033860A1 CA2033860A1 CA 2033860 CA2033860A CA2033860A1 CA 2033860 A1 CA2033860 A1 CA 2033860A1 CA 2033860 CA2033860 CA 2033860 CA 2033860 A CA2033860 A CA 2033860A CA 2033860 A1 CA2033860 A1 CA 2033860A1
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- Prior art keywords
- signal
- sensor
- electrical property
- condition
- basic electrical
- Prior art date
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- Indication And Recording Devices For Special Purposes And Tariff Metering Devices (AREA)
- Feedback Control In General (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A control system receives a condition signal from a sensor specifying by the value of a basic electrical property derivable from the condition signal the level of a preselected condition in a controlled apparatus, and responsive to the condition signal provides a control signal to the controlled apparatus to control the level of the preselected condition. To permit malfunctions in either the control system or the sensor to be efficiently isolated the control system further includes: an encoder which receives the condition signal and provides a signal digitally encoding the value of the basic electrical property in the condition signal, a display which receives the digitally encoded signal and provides a visible display of the digitally encoded value, and a manually operable selector allowing the operator to gate the signal from the encoder to the display by properly manipulating an element of the selector. When a malfunction is suspected, the operator manipulates the selector element to gate the signal from the encoder to the display and notes the value of the basic electrical property. (S)he then measures the basic electrical property in the sensor using an appropriate meter, detaching the sensor from the control system if appropriate. If the basic electrical property noted in the display is substantially unequal to the basic electrical property measured using the meter, this implies that the sensor is operating properly and the malfunction is probably in the control system. If the basic electrical property displayed by the display is substantially equal to the basic electrical property measured using the meter, then it is likely that the sensor is malfunctioning. In a preferred embodiment, the basic electrical property involved may be either electrical resistance or voltage.
A control system receives a condition signal from a sensor specifying by the value of a basic electrical property derivable from the condition signal the level of a preselected condition in a controlled apparatus, and responsive to the condition signal provides a control signal to the controlled apparatus to control the level of the preselected condition. To permit malfunctions in either the control system or the sensor to be efficiently isolated the control system further includes: an encoder which receives the condition signal and provides a signal digitally encoding the value of the basic electrical property in the condition signal, a display which receives the digitally encoded signal and provides a visible display of the digitally encoded value, and a manually operable selector allowing the operator to gate the signal from the encoder to the display by properly manipulating an element of the selector. When a malfunction is suspected, the operator manipulates the selector element to gate the signal from the encoder to the display and notes the value of the basic electrical property. (S)he then measures the basic electrical property in the sensor using an appropriate meter, detaching the sensor from the control system if appropriate. If the basic electrical property noted in the display is substantially unequal to the basic electrical property measured using the meter, this implies that the sensor is operating properly and the malfunction is probably in the control system. If the basic electrical property displayed by the display is substantially equal to the basic electrical property measured using the meter, then it is likely that the sensor is malfunctioning. In a preferred embodiment, the basic electrical property involved may be either electrical resistance or voltage.
Description
DIAGNOSTIC INTERPRETATION OF CONNECTED SENSORS
BACKGROUND OF INVENTION
Control systems which control the level of a preselected condition in controlled apparatus, typically receive the level of the preselected condition in the controlled apparatus in a condition signal from a sensor which specifies the level of the preselec.ted condition by the value of a basic electrical property of the sensor and which is derivable from the condition signal. There is a functional relationship between the value of the basic electrical property of the sPnsor and the level of tho preselected condition. The control system provides a control signal to the controlled apparatus which can cause the level of the preselected condition in the controlled apparatus to change as specified by the control signal. The control signal is changed by the control system responsive to the value o e the basic electrical property in the condition signal in a manner which shifts the level of the preselected condition toward a set point value for the preselected condition which has been established ~or the controlled apparatus.
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For example, the controlled apparatus may be a boiler and the preselected condition may be the temperature of the water in the boiler. The sensor selected then must provide an output which varies in a predictable fashion with water temperature. Such sensors may have as the basic electrical property their internal resistance or may provide a signal voltage, the level of either specifying the temperature sensed by the sensor.
In modern control systems it is customary to use a microprocPssor with properly designed software to comprise a part of the control system. The microprocessor receives from one source or another the desired set po~nt for the preselected condition and compares this set point with the level of the preselected condition as specified by the condition signal and then in response to deviations from the set point, provides control signals to a burner's fuel valve to heat the water in the boiler. It is customary now for such control systems to include a display. Some of the important information which is provided for the operator in the display is the microprocessor's internally recorded level of the preselected condition.
When the level of the preselected condition deviates from what is .
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- ~3--known to be a reasonable value or some other nonstandard aspect of the controlled system's behavior occurs, then a malfunction in either the control system or in the sensor is frequently the problem.
S Heretofore it often has been difficult to determine the source of the malfunction as being in either the sensor or the control system. What the servicer has done in the past is to measure the basic electrical property derived from the condition signal using the appropriate meter and measure the preselected condition using the appropriate thermometer or pressure gauge. The servicer ~hen consults a table specifying the relationship established for the sensor between its basic electrical property and the level of the preselected condition. If the level of the preselected condition derived from the table by use of the value of the basic electrical property is substantially the same as the level of that preselected condition ~etermined by direct measurement, then the malfunction is most likely in the control system because the level measured by the sensor agrees with the directly measured level of the preselected condition. If the preselected condition's level as derived from the table does not agree with the directly measured level of this condition, then it is ', -, 2 ~ C~
likely that the sensor itself is malfunctioning and should be replaced. The difficulties that arise with this approach to troubleshooting include the requirement to have and use the conversion properly and the necessity of having and using the specialized instrument that duplicates the measurement of the sensor.
BRIEF DESCRIPTION OF THE INVENTION
These problems are avoided by an improved design of the control system which is in most part implemented by changes in the basic control software executed by the microprocessor. In this way the microprocessor is altered to provide the functions for a conversion means which receives the condition signal from the sensor and provides a signal which digitally encodes the value of the basic electrical property derivable from the condition signal. The internal computer memory includes memory means which receives the signal from the conversion means, stores the value encoded in the signal from the conversion means, and provides a memory signal digitally encoding the stored value of the signal from the conversion means responsive to a read request signal. The display which is typically associated with the control system receives :
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, -5 ~ 3 digitally encoded signals from the memory means and provides a visible display of the digitally encoded value. These control systems further typically include a keyboard which comprises, in this embodiment, a manually operable selactor means including at least one key comprising a selector element which the human operator can manipulate to cause the selector means to supply a read request signal to the memory means responsive to a predetermined manipulation of the selector element. That is, by pressing the appropriate keys in the keyboard the memory means is caused to send to the display so that the human operator or service person can use it, a memory signal which encodes the stored value of the basic electrical property derivable from the condition signal.
When a malfunction is suspected in the apparatus controlling the level of the preselected condition, the operator will manipulate the selector element to gate the signal from the conversion means and stored by memory means to the display means. Using an appropriate meter the operator measures the value of the basic electrical property of the sensor. When the basic electrical property displayed by the display means is substantially unequal to the basic electrical property 25, ,' ' ' ~
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measured using the device then the most reasonable conclusion is that the malfunction is in the control system, and at least a part of the control system should be replaced. This could be for example, the microprocessor or any separate module forming a part of the control system, such as the A/D converter or any separate memory module which forms a part of the microprocessor. I~, on the other hand, the basic electrical property displayed by the display means is substantially equal to the basic electrical property measured using the device, then it is likely that the malfunction is in the sensor and the operator then replaces the sensor. The basic electrical property will typically comprise either sensor resistance or electrical voltage provided by the sensor.
A first purpose of the invention is to permit one to isolate a malfunction in control apparatus without the use of a specialized device for measuring the controlled condition.
A second purpose is to permit such a malfunction to be isolated without the necessity of a separate table to convert the value of the sensor's basic electrical property derivable $rom the condition signal.
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A third purpose of the invention is to make tha basic electrical property derivable from the condition signal easily available to the system operator or service person.
Other purposes of the invention will beco~e apparent from the description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diaqram of the control apparatus implementing this invention.
FIGS. 2 and 3 show specific embodiments of sensors which may be used in apparatus of FIG. 1.
DESCRIPTION OF THE PREFE~RED EMBODIMENTS
FIG. 1 shows a functional block diagram of the elements involved in this invention. When one inspects apparatus incorporating the invention, one sees controlled apparatus 9 which has a preselected condition the level of which is to be controlled by a control system. The control system includes a microprocessor 10 which contains the elements necessary to perform this control as well as many of the elements necessary to implement this invention. The microprocessor 10 can be considered to include possible elements external to its ~' ' ~ ;''. ' '' '~ ' package such as additional memory and A/D converter circuitry.
Operation of the microprocessor 10 is under the control of software stored in a read only memory (ROM) associated with the microprocessor 10. It should be understood that the software causes the microprocessor 10 to perform the functions of the individual elements shown in FIG. 1. The individual circuits of the microprocessor 10 thus provide the functions of the individual elements of FIG. 1 and in essence serve as these elements when the microprocessor 10 executes their functions. It is believed that one having ordinary skill in tha art can with the description which follows either design a hard wired system which performs the functions of the apparatus shown in FIG. 1 or can use the functional block diagram of FIG. 1 as a software flow chart from which to develop software which implements the invention of FIG. 1 in a computer or microprocessor of the designer's choice.
There is in FIG. 1 a sensor 22 within or adjacent to controlled apparatus 9 which provides a condition signal specifying the level of the preselected condition by the value of a basic electrical property derivable from the condition signal. Microprocessor 10 :. :
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provides a control signal on path ~0 to which controlled apparatus ~ responds by changing the level of the preselected condition as specified by the control signal. There is also a keyboard 20 which can be manipulated by an operator to provide an input to the microprocessor 10 and a display 21 receiving an output from the microprocessor 10 and visually displaying the digitally encoded value in the signal from path 35.
Keyboard 20 includes one or more keys or switches 23 each of which comprise a selector element by which a human may manually provide input signals to microprocessor 10.
There are any number of different types of devices which can comprise the controlled apparatus 9.
one typical example may be a water heater or boiler in which case sensor 22 comprises a temperature or a pressure sensor. Controlled apparatus 9 can alternatively be a motor actuator whose angular orientation or translational position is sensed by sensor 22 whose output signal on path 26 specifies the linear or angular position of the actuator. These examples are most certainly not exhaustive.
Sensor 22 specifies the level of the preselecte~ condition of controlled apparatus 9 by the -10- ~ ~ s~ 4i~
value of a basic electrical property derivable from the condition signal. Typically, this basic electrical property will comprise either voltage provided by the sensor 22 or the internal resistance or impedance of sensor 22, either of which change in response to change in the preselected condition. If voltage, sensor 22 will take the general form shown in FIG. 2 where the sensing element 50 comprises a variable voltage source whose voltage depends on the level of the preselected 10 condition. If this condition is temperature, for example, element S0 may comprise one junction of a thermocouple. FIG. 3 shows a sensor 22 comprising a variable resistance 60, where the actual resistance value of element 60 varies with temperature. There are 15 other types of sensors as well whose output is derivable from a change in the sensor's voltage or in the sensor element's resistance or impedance. These devices are well know to those familiar with the design of control ~ystems.
The output of sensor 22 is provided on a signal path 26 which is connected to an input channel 11 of microprocessor 10 by a connector 27. Since the basic premise of this invention is that location of a malfunction should be limited to either the sensor 22 or ' ;':' ' ,-~ , the control system so that the malfunction~ ~ uh~ an be replaced, it stands ko reason that the sensor 22 will be easily detachable from the control system. The output of input channel 11 is provided on a path 28 to a conversion means comprising converter 12. Converter 12 receives the condition signal and provides two digitally encoded output signals on paths 29 and 30. Path 29 carries a signal which digitally encodes the value of the basic electrical property in tha condition signal on path 28. Path 30 carries a signal digitally encoding the level of the preselected condition in the controlled apparatus 9. This raquires that converter 12 have available to it the functional relationship be~ween the basic electrical property in the signal on path 28 and the level of preselected condition in controlled apparatus 9. This can be provided as data input forming a part of the software or as a separate input provided when a particular sensor 22 type is attached to the control system.
Memory 13 receives the two digital signals carried on paths 29 and 30 and stores them in memory locations shown diagramatically as elements 13a and 13b respectively. Memory 13 will typically comprise the random access memory (RAM) in or associated with ?~
microprocessor 10. Memory elements 13a and 13b may ~hus simply be storage locations in such a RAM or conceivably may comprise special arithmetic registers within microprocessor 10. A read request signal on path 33 specifies individual storage elements in memory 13 such as elements 13a and 13b, and causes a signal digitally encoding the values stored in the selected elements to be provided on paths 41. Similarly, a read request signal from the control algorithm element specifies a memory element in memory 13 whose contents are to be placed on path 42. It is convenient for this representation to assume that the digital value of the basic electrical property is provided on path 41 and the level of the predetermined condition is provided on path 42.
During normal operation the control algorithm element 35 provides a read request signal on path 43 causing memory 13 to provide the level of the preselected condition on path 42. Control algorithm element 35 also receives a set point value on path 44 ~nd other miscellaneous data values on path 45 necessary to implement an algorithm in element 35 which will efficiently control the level of the preselected condition. Responsive to these various inputs, element ` ~
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35 provides a control signal on path 3~ to an output channel 37. Channel 37 provides a further control signal on path 40 directing controlled apparatus 9 to change the level of the preselected condition to more closely match the set point sncoded in the signal on path 44.
During troubleshooting when malfunction of the system is suspected, an operator manipulates a keyboard 20 having one or more control keys 23. By properly manipulating keys 23 a signal is genera~ed on path 31 to channel 14. This signal is further passed on path 32 to an interpreter 15 which generates a signal on path 33 specifying the appropriate memory elements in memory 13 to be provided on path ~1 to output channel element 38.
Output channel 38 responds with a signal on path 39 causing display element 21 to provide a visual display of the digital value encoded in the memory element selected by the signal on path 33. It is possible by appropriately manipulating the keys 23 of keyboard 20 to cause either one or both of the values of the basic electrical property digitally recorded in memory e;ement 13a or the level of the preselected condition recorded in memory element 13b, to be provided on path 41 and displayed vi~ually by display element 21.
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When malfunction is suspected in this control apparatus, it will typically occur either in the sensor 22 or within the microprocessor lO. The operator manipulates the keys 23 on keyboard 20 to cause display 21 to visually display the value of the basic electrical property in the condition signal on path 26. An appropriate meter 45 is connected by signal path 26a to path 26 to measure the value of the basic electrical property independently. The value of this basic electrical property displayed by meter 45 is compared by the repair person wi~h the value displayed for the basic electrical property in display 21. If the values are substantially equal then it is likely that the control system is properly interpreting the value of the basic electrical property, and the implication is that sensor 22 is malfunctioning, so the repair person replaces sensor 22. If the value displayed by meter 45 for the value o~ the basic electrical quantity is substantially unequal to the value displayed by display 21 for the same quantity, then the implication is that there is a malfunction somewhere within microprocessor 10. The repair person then replaces all or individual replaceable modules of microprocessor 10, in essence replacing at least a part of the control system as each .,. . ~ , module is replaced.
The type of meter 4S required depends on the type of sensor involved. If the sensor 22 uses as its basic electrical property rasistance (FIG. 3) then it is necessary to disconnect sensor 22 from input channel 11 by removing connector 27 when measuring the value of its basic electrical property so as to isolate the sensor from the effect~ of the channel ll itself. If sensor 22 is one of the type which generates a variable voltage (FIG. 2) which specifies the level o~ thP preselected condition by the value of the voltage generated then there typically will be no need to detach connector 27 from input channel 11. Meter 45 in this case need simply be of a high enough impedance and employ suitably shielded cables so that attaching meter 45 will not affect the signal carried on path 26.
Havinq thus described my invention, what I wish to claim by letters patent is:
: ;
BACKGROUND OF INVENTION
Control systems which control the level of a preselected condition in controlled apparatus, typically receive the level of the preselected condition in the controlled apparatus in a condition signal from a sensor which specifies the level of the preselec.ted condition by the value of a basic electrical property of the sensor and which is derivable from the condition signal. There is a functional relationship between the value of the basic electrical property of the sPnsor and the level of tho preselected condition. The control system provides a control signal to the controlled apparatus which can cause the level of the preselected condition in the controlled apparatus to change as specified by the control signal. The control signal is changed by the control system responsive to the value o e the basic electrical property in the condition signal in a manner which shifts the level of the preselected condition toward a set point value for the preselected condition which has been established ~or the controlled apparatus.
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For example, the controlled apparatus may be a boiler and the preselected condition may be the temperature of the water in the boiler. The sensor selected then must provide an output which varies in a predictable fashion with water temperature. Such sensors may have as the basic electrical property their internal resistance or may provide a signal voltage, the level of either specifying the temperature sensed by the sensor.
In modern control systems it is customary to use a microprocPssor with properly designed software to comprise a part of the control system. The microprocessor receives from one source or another the desired set po~nt for the preselected condition and compares this set point with the level of the preselected condition as specified by the condition signal and then in response to deviations from the set point, provides control signals to a burner's fuel valve to heat the water in the boiler. It is customary now for such control systems to include a display. Some of the important information which is provided for the operator in the display is the microprocessor's internally recorded level of the preselected condition.
When the level of the preselected condition deviates from what is .
.
".
~ ~ 5r~r ~
- ~3--known to be a reasonable value or some other nonstandard aspect of the controlled system's behavior occurs, then a malfunction in either the control system or in the sensor is frequently the problem.
S Heretofore it often has been difficult to determine the source of the malfunction as being in either the sensor or the control system. What the servicer has done in the past is to measure the basic electrical property derived from the condition signal using the appropriate meter and measure the preselected condition using the appropriate thermometer or pressure gauge. The servicer ~hen consults a table specifying the relationship established for the sensor between its basic electrical property and the level of the preselected condition. If the level of the preselected condition derived from the table by use of the value of the basic electrical property is substantially the same as the level of that preselected condition ~etermined by direct measurement, then the malfunction is most likely in the control system because the level measured by the sensor agrees with the directly measured level of the preselected condition. If the preselected condition's level as derived from the table does not agree with the directly measured level of this condition, then it is ', -, 2 ~ C~
likely that the sensor itself is malfunctioning and should be replaced. The difficulties that arise with this approach to troubleshooting include the requirement to have and use the conversion properly and the necessity of having and using the specialized instrument that duplicates the measurement of the sensor.
BRIEF DESCRIPTION OF THE INVENTION
These problems are avoided by an improved design of the control system which is in most part implemented by changes in the basic control software executed by the microprocessor. In this way the microprocessor is altered to provide the functions for a conversion means which receives the condition signal from the sensor and provides a signal which digitally encodes the value of the basic electrical property derivable from the condition signal. The internal computer memory includes memory means which receives the signal from the conversion means, stores the value encoded in the signal from the conversion means, and provides a memory signal digitally encoding the stored value of the signal from the conversion means responsive to a read request signal. The display which is typically associated with the control system receives :
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, -5 ~ 3 digitally encoded signals from the memory means and provides a visible display of the digitally encoded value. These control systems further typically include a keyboard which comprises, in this embodiment, a manually operable selactor means including at least one key comprising a selector element which the human operator can manipulate to cause the selector means to supply a read request signal to the memory means responsive to a predetermined manipulation of the selector element. That is, by pressing the appropriate keys in the keyboard the memory means is caused to send to the display so that the human operator or service person can use it, a memory signal which encodes the stored value of the basic electrical property derivable from the condition signal.
When a malfunction is suspected in the apparatus controlling the level of the preselected condition, the operator will manipulate the selector element to gate the signal from the conversion means and stored by memory means to the display means. Using an appropriate meter the operator measures the value of the basic electrical property of the sensor. When the basic electrical property displayed by the display means is substantially unequal to the basic electrical property 25, ,' ' ' ~
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measured using the device then the most reasonable conclusion is that the malfunction is in the control system, and at least a part of the control system should be replaced. This could be for example, the microprocessor or any separate module forming a part of the control system, such as the A/D converter or any separate memory module which forms a part of the microprocessor. I~, on the other hand, the basic electrical property displayed by the display means is substantially equal to the basic electrical property measured using the device, then it is likely that the malfunction is in the sensor and the operator then replaces the sensor. The basic electrical property will typically comprise either sensor resistance or electrical voltage provided by the sensor.
A first purpose of the invention is to permit one to isolate a malfunction in control apparatus without the use of a specialized device for measuring the controlled condition.
A second purpose is to permit such a malfunction to be isolated without the necessity of a separate table to convert the value of the sensor's basic electrical property derivable $rom the condition signal.
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A third purpose of the invention is to make tha basic electrical property derivable from the condition signal easily available to the system operator or service person.
Other purposes of the invention will beco~e apparent from the description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diaqram of the control apparatus implementing this invention.
FIGS. 2 and 3 show specific embodiments of sensors which may be used in apparatus of FIG. 1.
DESCRIPTION OF THE PREFE~RED EMBODIMENTS
FIG. 1 shows a functional block diagram of the elements involved in this invention. When one inspects apparatus incorporating the invention, one sees controlled apparatus 9 which has a preselected condition the level of which is to be controlled by a control system. The control system includes a microprocessor 10 which contains the elements necessary to perform this control as well as many of the elements necessary to implement this invention. The microprocessor 10 can be considered to include possible elements external to its ~' ' ~ ;''. ' '' '~ ' package such as additional memory and A/D converter circuitry.
Operation of the microprocessor 10 is under the control of software stored in a read only memory (ROM) associated with the microprocessor 10. It should be understood that the software causes the microprocessor 10 to perform the functions of the individual elements shown in FIG. 1. The individual circuits of the microprocessor 10 thus provide the functions of the individual elements of FIG. 1 and in essence serve as these elements when the microprocessor 10 executes their functions. It is believed that one having ordinary skill in tha art can with the description which follows either design a hard wired system which performs the functions of the apparatus shown in FIG. 1 or can use the functional block diagram of FIG. 1 as a software flow chart from which to develop software which implements the invention of FIG. 1 in a computer or microprocessor of the designer's choice.
There is in FIG. 1 a sensor 22 within or adjacent to controlled apparatus 9 which provides a condition signal specifying the level of the preselected condition by the value of a basic electrical property derivable from the condition signal. Microprocessor 10 :. :
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provides a control signal on path ~0 to which controlled apparatus ~ responds by changing the level of the preselected condition as specified by the control signal. There is also a keyboard 20 which can be manipulated by an operator to provide an input to the microprocessor 10 and a display 21 receiving an output from the microprocessor 10 and visually displaying the digitally encoded value in the signal from path 35.
Keyboard 20 includes one or more keys or switches 23 each of which comprise a selector element by which a human may manually provide input signals to microprocessor 10.
There are any number of different types of devices which can comprise the controlled apparatus 9.
one typical example may be a water heater or boiler in which case sensor 22 comprises a temperature or a pressure sensor. Controlled apparatus 9 can alternatively be a motor actuator whose angular orientation or translational position is sensed by sensor 22 whose output signal on path 26 specifies the linear or angular position of the actuator. These examples are most certainly not exhaustive.
Sensor 22 specifies the level of the preselecte~ condition of controlled apparatus 9 by the -10- ~ ~ s~ 4i~
value of a basic electrical property derivable from the condition signal. Typically, this basic electrical property will comprise either voltage provided by the sensor 22 or the internal resistance or impedance of sensor 22, either of which change in response to change in the preselected condition. If voltage, sensor 22 will take the general form shown in FIG. 2 where the sensing element 50 comprises a variable voltage source whose voltage depends on the level of the preselected 10 condition. If this condition is temperature, for example, element S0 may comprise one junction of a thermocouple. FIG. 3 shows a sensor 22 comprising a variable resistance 60, where the actual resistance value of element 60 varies with temperature. There are 15 other types of sensors as well whose output is derivable from a change in the sensor's voltage or in the sensor element's resistance or impedance. These devices are well know to those familiar with the design of control ~ystems.
The output of sensor 22 is provided on a signal path 26 which is connected to an input channel 11 of microprocessor 10 by a connector 27. Since the basic premise of this invention is that location of a malfunction should be limited to either the sensor 22 or ' ;':' ' ,-~ , the control system so that the malfunction~ ~ uh~ an be replaced, it stands ko reason that the sensor 22 will be easily detachable from the control system. The output of input channel 11 is provided on a path 28 to a conversion means comprising converter 12. Converter 12 receives the condition signal and provides two digitally encoded output signals on paths 29 and 30. Path 29 carries a signal which digitally encodes the value of the basic electrical property in tha condition signal on path 28. Path 30 carries a signal digitally encoding the level of the preselected condition in the controlled apparatus 9. This raquires that converter 12 have available to it the functional relationship be~ween the basic electrical property in the signal on path 28 and the level of preselected condition in controlled apparatus 9. This can be provided as data input forming a part of the software or as a separate input provided when a particular sensor 22 type is attached to the control system.
Memory 13 receives the two digital signals carried on paths 29 and 30 and stores them in memory locations shown diagramatically as elements 13a and 13b respectively. Memory 13 will typically comprise the random access memory (RAM) in or associated with ?~
microprocessor 10. Memory elements 13a and 13b may ~hus simply be storage locations in such a RAM or conceivably may comprise special arithmetic registers within microprocessor 10. A read request signal on path 33 specifies individual storage elements in memory 13 such as elements 13a and 13b, and causes a signal digitally encoding the values stored in the selected elements to be provided on paths 41. Similarly, a read request signal from the control algorithm element specifies a memory element in memory 13 whose contents are to be placed on path 42. It is convenient for this representation to assume that the digital value of the basic electrical property is provided on path 41 and the level of the predetermined condition is provided on path 42.
During normal operation the control algorithm element 35 provides a read request signal on path 43 causing memory 13 to provide the level of the preselected condition on path 42. Control algorithm element 35 also receives a set point value on path 44 ~nd other miscellaneous data values on path 45 necessary to implement an algorithm in element 35 which will efficiently control the level of the preselected condition. Responsive to these various inputs, element ` ~
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35 provides a control signal on path 3~ to an output channel 37. Channel 37 provides a further control signal on path 40 directing controlled apparatus 9 to change the level of the preselected condition to more closely match the set point sncoded in the signal on path 44.
During troubleshooting when malfunction of the system is suspected, an operator manipulates a keyboard 20 having one or more control keys 23. By properly manipulating keys 23 a signal is genera~ed on path 31 to channel 14. This signal is further passed on path 32 to an interpreter 15 which generates a signal on path 33 specifying the appropriate memory elements in memory 13 to be provided on path ~1 to output channel element 38.
Output channel 38 responds with a signal on path 39 causing display element 21 to provide a visual display of the digital value encoded in the memory element selected by the signal on path 33. It is possible by appropriately manipulating the keys 23 of keyboard 20 to cause either one or both of the values of the basic electrical property digitally recorded in memory e;ement 13a or the level of the preselected condition recorded in memory element 13b, to be provided on path 41 and displayed vi~ually by display element 21.
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When malfunction is suspected in this control apparatus, it will typically occur either in the sensor 22 or within the microprocessor lO. The operator manipulates the keys 23 on keyboard 20 to cause display 21 to visually display the value of the basic electrical property in the condition signal on path 26. An appropriate meter 45 is connected by signal path 26a to path 26 to measure the value of the basic electrical property independently. The value of this basic electrical property displayed by meter 45 is compared by the repair person wi~h the value displayed for the basic electrical property in display 21. If the values are substantially equal then it is likely that the control system is properly interpreting the value of the basic electrical property, and the implication is that sensor 22 is malfunctioning, so the repair person replaces sensor 22. If the value displayed by meter 45 for the value o~ the basic electrical quantity is substantially unequal to the value displayed by display 21 for the same quantity, then the implication is that there is a malfunction somewhere within microprocessor 10. The repair person then replaces all or individual replaceable modules of microprocessor 10, in essence replacing at least a part of the control system as each .,. . ~ , module is replaced.
The type of meter 4S required depends on the type of sensor involved. If the sensor 22 uses as its basic electrical property rasistance (FIG. 3) then it is necessary to disconnect sensor 22 from input channel 11 by removing connector 27 when measuring the value of its basic electrical property so as to isolate the sensor from the effect~ of the channel ll itself. If sensor 22 is one of the type which generates a variable voltage (FIG. 2) which specifies the level o~ thP preselected condition by the value of the voltage generated then there typically will be no need to detach connector 27 from input channel 11. Meter 45 in this case need simply be of a high enough impedance and employ suitably shielded cables so that attaching meter 45 will not affect the signal carried on path 26.
Havinq thus described my invention, what I wish to claim by letters patent is:
: ;
Claims (7)
1. In a control system providing a control signal to controlled apparatus to control the level of a preselected condition therein and receiving at least one condition signal from at least one sensor specifying the level of the preselected condition by the value of a basic electrical property derivable from the condition signal, and responsive to the basic electrical property modifying the control signal, an improvement allowing efficient isolation of a malfunction occurring in either the control system or the sensor, comprising a) conversion means receiving the condition signal for providing a signal digitally encoding the value of the basic electrical property derivable from the condition signal;
b) memory means receiving the signal from the conversion means for storing the value encoded in the signal from the conversion means and for providing a memory signal digitally encoding the stored value responsive to a read request signal;
c) display means for receiving a digitally encoded signal from the memory means and for providing a visible display of the digitally encoded value; and d) manually operable selector means including a selector element for human manipulation for supplying a read request signal to the memory means responsive to a predetermined manipulation of the selector element.
b) memory means receiving the signal from the conversion means for storing the value encoded in the signal from the conversion means and for providing a memory signal digitally encoding the stored value responsive to a read request signal;
c) display means for receiving a digitally encoded signal from the memory means and for providing a visible display of the digitally encoded value; and d) manually operable selector means including a selector element for human manipulation for supplying a read request signal to the memory means responsive to a predetermined manipulation of the selector element.
2. The apparatus of claim 1, wherein the basic electrical property is electrical resistance, and wherein the conversion means includes means for providing a signal digitally encoding the electrical resistance of the sensor.
3. A method employing the apparatus of claim 2, including the steps of:
a) manipulating the selector element to gate the signal from the conversion means to the display means;
b) detaching the sensor from the control system;
c) measuring the electrical resistance in the sensor using a resistance meter;
d) when the electrical resistance displayed by the display means is substantially unequal to the electrical resistance measured using the resistance meter, replacing at least a part of the control system;
and e) when the electrical resistance displayed by the display means is substantially equal to the electrical resistance measured using the resistance meter, replacing the sensor.
a) manipulating the selector element to gate the signal from the conversion means to the display means;
b) detaching the sensor from the control system;
c) measuring the electrical resistance in the sensor using a resistance meter;
d) when the electrical resistance displayed by the display means is substantially unequal to the electrical resistance measured using the resistance meter, replacing at least a part of the control system;
and e) when the electrical resistance displayed by the display means is substantially equal to the electrical resistance measured using the resistance meter, replacing the sensor.
4. A method employing the apparatus of claim 1, including the steps of:
a) manipulating the selector element to gate the signal from the conversion means to the display means:
b) measuring the basic electrical property in the sensor using an appropriate device:
c) when the basic electrical property displayed by the display means is substantially unequal to the basic electrical property measured using the device, replacing at least a part of the control system; and d) when the basic electrical property displayed by the display means is substantially equal to the basic electrical property measured using the device, replacing the sensor.
a) manipulating the selector element to gate the signal from the conversion means to the display means:
b) measuring the basic electrical property in the sensor using an appropriate device:
c) when the basic electrical property displayed by the display means is substantially unequal to the basic electrical property measured using the device, replacing at least a part of the control system; and d) when the basic electrical property displayed by the display means is substantially equal to the basic electrical property measured using the device, replacing the sensor.
5. The apparatus of claim 1, wherein the basic electrical property is electrical voltage, and wherein the conversion means includes means for providing a signal digitally encoding the electrical voltage of the condition signal provided by the sensor.
6. A method employing the apparatus of claim 5, including the steps of:
a) manipulating the selector element to gate the signal from the conversion means to the display means;
b) measuring the electrical voltage of the condition from the sensor using a voltmeter;
c) when the electrical voltage displayed by the display means is substantially unequal to the electrical voltage measured using the voltmeter, replacing at least a part of the control system: and d) when the electrical voltage displayed by the display means is substantially equal to the electrical voltage measured using the voltmeter, replacing the sensor.
a) manipulating the selector element to gate the signal from the conversion means to the display means;
b) measuring the electrical voltage of the condition from the sensor using a voltmeter;
c) when the electrical voltage displayed by the display means is substantially unequal to the electrical voltage measured using the voltmeter, replacing at least a part of the control system: and d) when the electrical voltage displayed by the display means is substantially equal to the electrical voltage measured using the voltmeter, replacing the sensor.
7. The improvement of claim 1 wherein the control system further includes means to provide a condition signal encoding the level of the preselected condition as a function of the basic electrical property; and wherein the conversion means further provides a units signal digitally encoding the level of the preselected condition in physical units; wherein the memory means receives the units signal, stores the value encoded in the units signal, and provides a units memory.
signal digitally encoding the stored value of the units signal responsive to a units read request signal; said improvement further comprising in the manually operable selector means, means for supplying a units read request signal to the memory means responsive to a predetermined manipulation of the selector element.
signal digitally encoding the stored value of the units signal responsive to a units read request signal; said improvement further comprising in the manually operable selector means, means for supplying a units read request signal to the memory means responsive to a predetermined manipulation of the selector element.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US47018190A | 1990-01-25 | 1990-01-25 | |
| US07/470,181 | 1990-01-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2033860A1 true CA2033860A1 (en) | 1991-07-26 |
Family
ID=23866590
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2033860 Abandoned CA2033860A1 (en) | 1990-01-25 | 1991-01-09 | Diagnostic interpretation of connected sensors |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2033860A1 (en) |
-
1991
- 1991-01-09 CA CA 2033860 patent/CA2033860A1/en not_active Abandoned
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