Analysis of a sigma-delta resistance-to-digital converter for differential resistive sensors

A direct resistance-to-digital converter (RDC) that is suitable for differential resistive sensors is proposed and analyzed in this paper. The RDC presented here provides a digital output that is linearly proportional to the parameter being sensed by a differential resistive sensor possessing either linear or inverse characteristics. The RDC employs the sigma-delta analog-to-digital conversion (Σ-Δ ADC) principle and, hence, possesses all the advantages and limitations of such an ADC. Analysis shows that the proposed RDC has negligible sensitivity to variations in circuit parameters. Experimental results on a prototype built and tested gave a worst-case error < 0.15%, establishing the efficacy of the proffered RDC. © 2009 IEEE.