UVVF Tuning Fork Level Switch probe is based on a tuning fork harmonic resonance. It utilizes piezoelectric devices to drive the fork to vibrate and detect the changes of vibration. The fork vibrates in resonant frequency when it does not contact with medium. Once the fork comes in contact with medium, vibrating amplitude of the fork will decrease substantially. Output from the detecting piezoelectric device will decrease accordingly. An integrated circuit is designed to analyze the amount of decrease and output a switch signal.