A Resistance Deviation-to-Pulsewidth Converter for Resistive Sensors

A resistance deviation-to-pulsewidth converter is presented for interfacing resistive sensors. It consists of a ramp integrator, two resistance-tunable Schmitt triggers, and two logic gates. A prototype circuit built using discrete components exhibits a resolution as high as 14 bits and a linearity error less than plusmn0.06% when the output pulse is counted by a 10-MHz clock signal. The proposed circuit is applied to measure the temperature difference with the platinum resistance temperature detectors. The measured conversion sensitivity of the temperature difference-to-pulsewidth converter is 5.74 mus/degC, and its linearity error is less than plusmn1% in the temperature difference range of 0degC to 100degC.