Self-Balancing Signal Conditioning Circuit for a Floating-Wiper Resistive Displacement Sensor

The limited operating life of conventional resistive displacement sensor is due to wear and tear because the wiper has to rub against the resistive element during operation. This problem can be eliminated by using a floating wiper. However, the absence of electrical contact between the wiper and the resistive element demands the use of complex signal conditioning circuitry to obtain an output proportional to displacement. We now propose a simple self-balancing signal conditioning circuit suitable for a floating wiper resistive displacement sensor that provides an output linear to the displacement. The proposed signal conditioning circuit employs only a single dc reference voltage and provides an output that is independent of the coupling capacitance that arises between the floating wiper and the resistive element. Hence, errors due to mismatch between reference voltages and variations in the coupling capacitance are completely eliminated. The results obtained from simulation studies and the tests conducted on a prototype built, establish the efficacy of the proposed method. Analysis of the proposed scheme presented here establishes the ground rules for avoiding pitfalls in the design stage itself.