A microcontroller sensor interface suitable for resistive sensors with large lead resistance

Abstract

A direct resistive sensor interface to a microcontroller reported earlier, works well only if the sensor element is very close to the micro-controller pins. If the sensor element is at a distance from the micro-controller then the lead resistance due to connecting wires between resistive sensor element and the micro-controller introduces appreciable errors in the output. A modified scheme of direct sensor interface to micro-controller is presented here. In the proposed scheme, the effect of lead resistances is compensated and thus the proposed direct resistive sensor interface to a micro-controller works well even if the sensor is kept at distance and connected through long connecting wires. Since the lead wire resistance is compensated, automatic temperature compensation (temperature effect of lead wires) is obtained. The results obtained from simulation and experimental results recorded from a prototype of the proposed scheme establishes the effectiveness of the proposed method in eliminating the effect of lead resistance in the output. Worst-case error noted in the simulation output was < ± 0.23 % and the worst-case error of the prototype unit was found to be < ± 0.33 %.