Automatic Bridge-based Interface for Differential Capacitive Full Sensing

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• 作者：G. Ferri ; ^{giuseppe.ferri@univaq.it} ; F.R. Parente ; V. Stornelli ; G. Barile ; L. Pantoli
• 关键词：Differential capacitance sensors ; bridge-based circuits ; analog circuits ; Wheatstone bridge ; electronic interface.
• 刊名：Procedia Engineering
• 出版年：2016
• 出版时间：2016
• 年：2016
• 卷：168
• 期：Complete
• 页码：1585-1588
• 全文大小：252 K
• 卷排序：168

文摘

The authors here propose, for the first time, an automatic analog interface for differential capacitance estimation, able to reveal and quantify both low and high (full-range) capacitive variations. The working principle is based on a modified De-Sauty AC bridge configuration where two differential capacitances and two resistances are employed, one of which is implemented by a Voltage Controlled Resistor (VCR). Through a suitable feedback loop, a very accurate estimation over the complete range of the differential capacitance variation is possible, while the bridge allows a continuous differential capacitance evaluation without the need of knowing the accurate value of the sensor baseline and/or its variation range. A general but very simple formula, considering both the “autobalancing” and the “out-of-equilibrium” ranges, is also given. Theoretical, experimental and simulated results are in a very good agreement. Sensitivity and resolution values, typical of sensors and their interfaces, have been determined in a practical case, showing satisfactory values.