Linear and Sensitive Detection Electronics for Capacitive Sensors

摘要

This paper presents a linear, sensitive and simple signal conditioning circuit for capacitive sensors. The proposed two stage circuit comprises a capacitance to voltage conversion circuit then voltage to frequency converter. The capacitance to voltage conversion circuit is designed to compensate initial offset sensor capacitance. It is a challenge to measure small capacitance change in capacitive sensor with large initial offset capacitance. Therefore, compensation of initial offset capacitance of capacitive sensor based instrumentation system is demanded. The proposed linear and sensitive signal conditioning circuit effectively compensates initial offset capacitance of the capacitive sensor. The circuit is tested for a wide range of capacitance (57.74 pF-1050.9 pF) which gives adjusted R-squared equal to 0.99901 for a linear fit response characteristic. The sensitivity of the circuit is 71.24 Hz/pF. However, there is a trade-off between sensitivity and working range of the circuit.