An accurate interface for capacitive sensors

A new smart interface based on a first-order charge-balanced SC-oscillator is presented for capacitive sensors, which are shunted by a parasitic conductance. In the novel interface, the effect of shunting conductance is reduced by using the charge/discharge method. The effect of the stray capacitances is eliminated by using the two-port measurement. Moreover, all multiplicative and additive errors of the interface are also eliminated by using the auto-calibration technique and the chopping technique.