To provide a static capacitance proximity sensor capable of easily sensing an object to be sensed even when the object to be sensed is fertilizer or unhulled rice and sensing the object to be sensed being a sensing object without causing a malfunction even when a water drop or a solid matter is adhered to a sensing face.
The static capacitance proximity sensor is provided with: a sensing electrode 1 arranged in a sensor head; a shield electrode 2 provided to surround the surrounding of the sensing electrode 1; and an oscillation circuit 3 that oscillates a high frequency signal when the static capacitance of the sensing electrode 1 is changed by the approach of the object to be sensed and outputs the signal to a detection circuit of a signal processing circuit 4, wherein the oscillation circuit 3 connects the shield electrode 2 to the ground to bring the level of the electrode 2 to a zero level, the shield electrode 2 with the zero level increases the positive electric charge of the sensing electrode 1 by the application of a voltage and the increased number of the positive electric charge increases the static capacitance of the sensing electrode 1.
Kiyoshi Yasushima
Souji Sasaki
Noboru Omura
Takanashi Norio