A Semicylindrical Capacitive Sensor With Interface Circuit Used for Flow Rate Measurement

In this paper, a semicylindrical capacitive sensor with an interface circuit used for flow rate measurement is proposed. The numerical analysis method to calculate the capacitance of the semicylindrical capacitive sensor is analyzed and discussed. The picofarad-range capacitive variation of the semicylindrical capacitive sensor can be detected and converted into voltage variation by the interface circuit. Besides, the interface circuit is compact enough to simplify the circuit complexity and could be easily implemented for flow rate measurement. All the functions of the capacitive sensing method of the semicylindrical capacitive sensor used for flow rate measurement are proved successfully through HSPICE simulation. Measurement results have successfully confirmed the correct functions and performance of the semicylindrical capacitive sensor with an interface circuit used for flow rate measurement, which ranges from 0.136 to 4.746 L/min, on the liquid crystal display panel coating machine