The development of high-accuracy microprocessor based thermocouple calibrator

Abstract

A high-accuracy thermocouple calibrator is proposed in this paper. The calibrator is made up of 8031 single-chip microprocessor and can realize the measurement and calibration of 8 types of thermocouples. By outputting a signal simulating the thermocouple e.m.f., it can also calibrate the thermocouple transmitters, or instruments. To obtain high accuracy, some special designs are applied to the system hardware, including micro-voltage amplifiers, ADC and input unit, DAC circuits and output unit. In addition, some functions are achieved by the software that is written using MCS-51 assembling language, e.g., internal self-adjustment for the input and output signals, nonlinear correction of 8 types of thermocouples, data processing and cold junction compensation. All the relative messages are displayed using a LCD module. The instrument accuracy is better than /spl plusmn/0.05% for simulant E.M.F output; /spl plusmn/0.08% for measuring input thermocouple E.M.F signal for the temperature range of 0/spl deg/C- 2000/spl deg/C.