Process variable transmitter with EMF detection and correction

摘要

A preexisting voltage across a sensor is latched to a storage capacitor prior to any excitation current being applied to the sensor. Once the excitation current is applied, the voltage on the storage capacitor is directly subtracted from a differential voltage across the sensor. The subtraction is done before a measurement is converted to a digital value and passed to a transmitter. The subtraction is performed in hardware, and a time required to sample and hold the preexisting voltage across the storage capacitor is within a settling time used for collecting any sensor measurements.

主权项

1. A process variable transmitter, comprising:
an analog-to-digital (A/D) converter that receives a sensor signal from a sensor indicative of a sensed process variable, the sensor being controllable to receive a control signal and output the sensor signal in response to the control signal, the A/D converter converting the sensor signal into a digital signal; a processor, that provides the control signal to the sensor and that receives the digital signal and provides a measurement output indicative of the digital signal; and a detection component receiving a preexisting input from the sensor, prior to the processor providing the control signal to the sensor, and providing a detection signal to the processor indicative of a level of the preexisting input.