Current excitation method for ΔR measurement in piezo-resistive sensors with a 0.3-ppm resolution

Abstract

This paper presents a new highly sensitive (10 $muhbox{V}/hbox{ppm}$) bidirectional current excitation method for piezo-resistive sensor measurements, through excitation of two half bridges for $Delta{R}$ measurement. The proposed circuit is insensitive to thermoelectric and stray noise effects since it measures the peak-to-peak value of the generated voltage. Measurement results using resistors show that variations as low as 0.3 ppm are measurable from 15 $^{circ}hbox{C}$ to 80 $^{circ}hbox{C}$ with resistors. As an experimental application, 40 parts per billion variation in gas concentration using piezo-resistive SU-8 microcantilevers is measured by the proposed circuit at room temperature.