A Novel Capacitive Temperature Sensor for Real-Time Monitoring of Temperature in the Silicone Oil Fan Clutch

Abstract

This paper presents a novel capacitive sensor for real-time monitoring of temperature in the silicone oil fan clutch. The structure of the temperature sensor is designed and fabricated by the Silicon-On-Glass (SOG) process based on the bonding technology. The silicone oil is designed as the temperature sensing materials in the capacitive sensor. The capacitance of the embedded sensor is changing with respect to temperature of the silicone oil fan clutch. Experimental results show that the sensor provides a sensitivity of 27.3fF/°C in the -30 to 40°C range, 58.2fF/°C in the 50 to 110°C rang. It is also demonstrated that the temperature sensitive capacitor can be integrated with a copper inductance antenna and tests as a passive wireless temperature sensor. The resonant frequency of the inductor-capacitor (LC) resonator changes with respect to the changing capacitance. Then temperature changes can be remotely determined towards a frequency spectrum study. Experimental results show that the LC type passive wireless sensor provides a sensitivity of 6.35kHz/°C in the -30 to 110°C range.