Optimized Thermocouple Temperature Sensor using 555 Timer and ANN Based Linearization

Abstract

The presented work reports a low-cost, two-stage linearization scheme for thermocouple based temperature sensing. The first stage involves IC555 based astable multivibrator. An NTC thermistor is employed as a discharging resistor of multivibrator to facilitate reference junction compensation as well as the measurement of ambient temperature. The second stage of linearization employs ANN based fitting between the output of IC555 and true temperature. The linearization scheme uses a trade-off between the fast response of IC555 based arrangement and exorbitant accuracy of ANN-based arrangement, to optimize the performance of the sensor. The PSpice based simulation study is carried out with a T-type thermocouple for temperature range of 80°C to 125°C while the ambient temperature varies from 25°C up to 40°C. It offers absolute maximum full-scale error of 0.13%, as little as in the best existing literature, with a reduced computational burden upon the processing unit. Keywords—ANN, As table Multivibrator, IC555, Linearization, Temperature sensor.