Direct interface for capacitive sensors based on the charge transfer method

We present the theoretical analysis and experimental performance results of a direct interface for capacitive sensors based on the charge transfer method when parasitic capacitances are included. The interface circuit implements a two-point calibration technique that makes measurement results independent from voltage-and temperature-dependent parameters. The measurement deviation is below 1 % FSR (Full Scale Range) for capacitances from 10 pF to 1 nF.