Resistance based process control device diagnostics
First Claim
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1. A process control device in a process control system, comprising:
- an electrical element having an electrical resistance;
process control device circuitry coupled to the electrical element to perform a process control function;
self heating circuitry coupled to the electrical element providing a self heating signal related to a self heating index (SHI) representing an amount of degradation of the electrical element due to the electrical resistance;
circuitry coupled to a process control loop for coupling the device to the loop; and
diagnostic circuitry coupled to the self heating circuitry responsively providing a diagnostic output related to health of the electrical element as a function of the self heating signal.
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Abstract
A device in a process control system includes an electrical element which has a resistance. Self heating circuitry coupled to the element provides a self heating signal related to the resistance of the element. Diagnostic circuitry provides a diagnostic output as a function of the self heating signal output.
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Citations
38 Claims
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1. A process control device in a process control system, comprising:
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an electrical element having an electrical resistance;
process control device circuitry coupled to the electrical element to perform a process control function;
self heating circuitry coupled to the electrical element providing a self heating signal related to a self heating index (SHI) representing an amount of degradation of the electrical element due to the electrical resistance;
circuitry coupled to a process control loop for coupling the device to the loop; and
diagnostic circuitry coupled to the self heating circuitry responsively providing a diagnostic output related to health of the electrical element as a function of the self heating signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for diagnosing an electrical element in a process control device, comprising:
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obtaining a self heating index (SHI) representing an amount of degradation for an electrical element of the device, the electrical element having a resistance; and
providing an electrical element diagnostic output as a function of the SHI. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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26. A device for use in a process control system, comprising:
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I/O circuitry adapted to coupled to a process control loop;
an electrical element having a resistance;
a current source coupled to the electrical element to inject a current into the electrical element;
voltage measurement circuitry coupled to the electrical element providing an output related to voltage drop across the electrical element; and
diagnostic circuitry providing a self heating index (SHI) output representing an amount of degradation of the electrical element as a function of injected current and the voltage drop across the electrical element due to the resistance. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A process control device in a process control system, comprising:
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an electrical element having an electrical resistance;
process control device circuitry coupled to the electrical element to perform a process control function;
self heating circuitry coupled to the electrical element providing a self heating signal related to a self heating index (SHI) representing an amount of degradation of the electrical element due to the electrical resistance, the SHI defined as a change in resistance of an electrical element for a given change in power input to the element;
circuitry coupled to a process control loop for coupling the device to the loop; and
diagnostic circuitry coupled to the self heating circuitry responsively providing a diagnostic output related to health of the electrical element as a function of the self heating signal.
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37. A method for diagnosing an electrical element in a process control device, comprising:
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obtaining a self heating index (SHI) representing an amount of degradation for an electrical element of the device, the electrical element having a resistance, the SHI defined as a change in resistance of an electrical element for a given change in power input to the element; and
providing an electrical element diagnostic output as a function of the SHI.
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38. A device for use in a process control system, comprising:
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I/O circuitry adapted to couple to a process control loop;
an electrical element having a resistance;
a current source coupled to the electrical element to inject a current into the electrical element;
voltage measurement circuitry coupled to the electrical element providing an output related to voltage drop across the electrical element; and
diagnostic circuitry providing a self heating index (SHI) output representing an amount of degradation of the electrical element as a function of injected current and the voltage drop across the electrical element due to the resistance, the SHI defined as a change in resistance of an electrical element for a given change in power input to the element.
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Specification