Charge-transfer-based signal interface for differential capacitive sensors

Abstract

We propose a circuit to directly connect a differential capacitive sensor to a microcontroller unit (MCU), which is based on the charge-transfer method and does not need any calibration component. The performance has been tested by emulating the differential capacitive sensor with discrete components. The major uncertainty sources are residual stray capacitances. The maximal deviation obtained, referred to the Full Scale Span (FSS), is ±4 % for sensors with nominal capacitance C0 = 100 pF, and ±0,6 % for sensors with C0 = 1 nF.