Full range analog Wheatstone bridge-based automatic circuit for differential capacitance sensor evaluation

In this paper, an integrable novel fully analog Wheatstone bridge-based interface for differential capacitance estimation is presented. Its working principle takes advantage of the modified De-Sauty AC bridge configuration being employed only by two capacitors and two resistors. A feedback loop controls one of the resistors (e.g. a voltage-controlled resistor), to obtain an evaluation of the differential capacitance variation on a full range, thanks to a general but very simple formula that considers both the auto-balancing' and the bridge out-of-equilibrium' ranges. The proposed interface shows a satisfactory accuracy, being the percentage relative error within 0.45% for the experimental results. Copyright (c) 2016 John Wiley & Sons, Ltd.