期刊
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
卷 69, 期 8, 页码 5890-5899出版社
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TIM.2019.2962296
关键词
Capacitive sensors; Parasitic capacitance; Capacitors; Impedance; Sensitivity; Analog circuits; differential capacitive sensor; negative impedance converter (NIC); parasitic capacitance compensation
Capacitive sensors are popular, especially due to the possibility to be integrated together with the readout circuit. In particular, differential implementations are intrinsically insensitive to common-mode noise. Unfortunately, stray capacitances can significantly alter the sensor output value, worsening the performance. This article proposes a novel solution based on an autotuning feedback loop to compensate for parasitic effects, thus preserving measurement performance. In particular, a voltage-controlled negative impedance converter is driven by a feedback loop, in order to control the current flowing in the sensor. The proposed solution can work with the both linear and hyperbolic type of sensors and with any voltage-mode sensor interfaces. An experimental setup, comprising the proposed compensating circuit, a De-Sauty bridge-based sensor front end and an emulated sensor, has been arranged to evaluate obtainable performance. Results show that the linearity error is decreased from more than 10%, without compensation, to less than 1%, when the proposed system is applied.
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