초록 ▼

A temperature transmitter and a process control system includes a sensor input for coupling to a temperature sensor having a temperature dependent resistance. The resistance measuring circuitry couples to the sensor input and provides a resistance output related to resistance of the temperature depe

A temperature transmitter and a process control system includes a sensor input for coupling to a temperature sensor having a temperature dependent resistance. The resistance measuring circuitry couples to the sensor input and provides a resistance output related to resistance of the temperature dependent resistance. Analog to digital conversion circuitry couples to the sensor input and provides a digital output related to AC signals across the sensor input. Digital signal processing circuitry isolates a Johnson noise component of the AC signals and provides a digitized Johnson noise output. Temperature measurement circuitry provides a calibrated temperature output based upon the resistance output and the digitized Johnson noise output. Output circuitry transmits the calibrated temperature output over the process control loop.

대표청구항 ▼

[ What is claimed is:] [1.] A transmitter in a process control system, comprising:a sensor input for coupling to a temperature sensor having a temperature dependant resistance;resistance measuring circuitry coupled to the sensor input having resistance output related to resistance of the temperature

[ What is claimed is:] [1.] A transmitter in a process control system, comprising:a sensor input for coupling to a temperature sensor having a temperature dependant resistance;resistance measuring circuitry coupled to the sensor input having resistance output related to resistance of the temperature dependent resistance;an amplifier coupled to the sensor input providing an amplified output having an AC noise component and a Johnson noise component;analog to digital conversion circuitry coupled to the amplified output providing a digital output;digital signal processing circuitry coupled to the digital output for isolating the Johnson noise component and providing a digitized Johnson noise output;temperature measurement circuitry coupled to the resistance measurement circuitry and the digital signal processing circuitry providing a calibrated temperature output based upon the resistance output and the digitized Johnson noise output; andoutput circuitry for coupling to a process control loop and transmitting the calibrated temperature output over the loop.