Honeywell International Inc.
ENHANCING RTD MEASUREMENT ACCURACY BY MEANS OF VARIABLE EXCITATION CURRENT

Abstract:

A method, apparatus and system for measuring a temperature can involve measuring a voltage with a resistance temperature detector using a variable excitation current, and deriving a process temperature from the voltage measured by the resistance temperature detector. The process temperature can be further derived by applying a plurality of values of the variable excitation current, measuring corresponding values of voltage, and estimating a resistance by applying a least square estimation. The process temperature can also be derived by applying a different value of the variable excitation current at every iteration, using a recursive least square estimation to measure a resistance, and using confidence intervals for instrument diagnostics.