Microprocessor-based temperature indicator using thermocouple as the sensor

Abstract

A microprocessor-based thermocouple temperature indicator has been developed and described. For a k-type thermocouple, this indicator provides a linear performance over a Wide dynamic temperature range of 50 to lOOO QC with an accuracy of better than ± O.3°C. To carry out the linearization of thermocouple easily through software, the full-scale temperature range of the thermocouple IS divided into ten selectors and each is approximated by a fourth-order polynomial equation. The extract millivolt signal of the thermocouple from a high common-mode voltage (0 to ± 300 v peak),a flying-capacitor multiplexer to conjunction with drift-free dc amplifier is used us a signal conditioner. Test results are given to support the theory.