Patent ID: 6903558

Claim:
A digitizing ohmmeter system comprising: a switched excitation circuit coupled to excite an impedance-varying input sensor for generating an input voltage step indicative of the resistance of said input sensor; and an analog-to-digital converter (ADC) circuit coupled to sample said input voltage step and generate a resistance output signal, said ADC circuit comprising: a modulator coupled to integrate charge associated with said input voltage step and balance said charge with charge associated with a fullscale resistance reference signal, said modulator generating a digital output signal, said digital output signal forming a digital data stream over a plurality of sampling cycles where said digital data stream has an ones density proportional to the ratio of the resistance of said input sensor to said fullscale resistance reference signal; and post processing circuit coupled to receive said digital data stream and generating a digital number indicative of the occurrence of ones in said digital data stream within said plurality of sampling cycles as said resistance output signal.