Abstract: An electrostatic capacity sensor includes an electrostatic capacity type detection element in which a detection electrode, a ground electrode and a charge plate interposed between the detection electrode and the ground electrode are arranged in a state that they are isolated to each other; a detection circuit for detecting changes in capacitance of the detection electrode caused by an object to be detected; and a power supply for supplying electrical power to the detection circuit. Since the electrostatic capacity sensor is provided with the charge plate between the detection electrode and the charge plate, it is possible to improve the sensitivity of the detection element, so that it is possible to increase the detection distance. In addition, the variations in the capacitance of the detection element due to the changes in the ambient conditions can be reduced.

Abstract: It is an object of this invention to provide a fence sensor which can achieve an excellent detection stability without using a current for generating an electric field nor infrared rays. The fence sensor comprises a detection electrode (8); a reference electrode (9) insulated from the detection electrode (8); a chargeable member (4) insulated from both of the detection electrode (8) and the reference electrode (9); and a detection circuit (20) for detecting a change in the electrostatic capacitance between the detection electrode and the reference electrode that is generated by the presence of an object to be detected within a detection region of the detection electrode. In this fence sensor, the chargeable member is arranged such that at least a part of the chargeable member is situated within the detection region of the detection electrode. Further, the chargeable member is formed from a conductor.

Abstract: An electrostatic capacity sensor comprises an electrostatic capacity type detection element in which a detection electrode, a ground electrode and a charge plate interposed between the detection electrode and the ground electrode are arranged in a state that they are isolated to each other; a detection circuit for detecting changes in capacitance of the detection electrode caused by an object to be detected; and a power supply for supplying electrical power to the detection circuit. Since the electrostatic capacity sensor is provided with the charge plate between the detection electrode and the charge plate, it is possible to improve the sensitivity of the detection element, so that it is possible to increase the detection distance. In addition, the variations in the capacitance of the detection element due to the changes in the ambient conditions can be reduced.