A digitizing ohmmeter system for providing a digital resistance ratio measurement includes a high impedance current source providing a DC excitation current to an impedance-varying input sensor and a reference resistor and an ADC circuit including a charge-balancing modulator and a digital post processing circuit. The same DC excitation current passes through both the input sensor and the reference resistor. The system utilizes a switched capacitor input stage to sample the voltage across the input sensor and the voltage across the reference resistor to generate an input voltage step and a reference voltage step which are coupled to the modulator of the ADC circuit. The digitizing ohmmeter system thereby realizes fully ratiometric operation such that neither a precise current source nor a precise voltage source is required for accurate resistance ratio measurements and only a stable known reference resistor is necessary for accurate absolute resistance measurements.