Design and Performance Studies of a Simple Direct Digital Electronic Instrumentation System for Thermistor Interfacing

The paper proposes a direct-digital interfacing circuit for linearization of thermistors. The proposed circuit comprises a switched passive linearized network and a simple relaxation-oscillator circuit for digitization. The salient features of the proposed scheme include, 1) simple architecture for thermistor linearization, 2) direct-digital output, without requiring analog-to-digital conversion, 3) usage of a single (uni-polar) reference voltage. The working principle of the interfacing system is established using a detailed mathematical derivation. The efficacy of the proposed digitizer is evaluated using simulation and hardware experiment studies, over different range of temperatures. Results demonstrate that the interfacing system can work very well for the temperatures considered. This digital converter can find number of applications, in aviation, aerospace and other industrial sectors.