Diagnostics for resistance based transmitter

摘要

Transmitter in a process control system includes a resistance sensor sensing a process variable and providing a sensor output. Sensor monitoring circuitry coupled to the sensor provides a secondary signal related to the sensor. Analog-to-digital conversion circuitry coupled to the sensor output and the sensor monitoring circuitry provides a digitized sensor output and a digitized secondary signal. Output circuitry coupled to a process control loop transmits a residual life estimate related to residual life of the sensor. A memory stores a set of expected results related to the secondary signal and to the sensor. Diagnostic circuitry provides the residual life estimate as a function of the expected results stored in the memory, the digitized sensor output and the digitized secondary signal.