Capacitance coupled sensor and substance detecting method using capacitance-coupled sensor

Abstract

To allow a DC voltage to be obtained as an output signal for higher versatility. A sensor unit 400 has three electrodes: a transmission electrode 401, a reception electrode 402 and a shielding electrode 403. The shielding electrode 403 shields the transmission electrode 401 and the reception electrode 402 from each other in terms of high-frequency and is constantly earthed. A high-frequency voltage is applied to the transmission electrode 401 from a high-frequency oscillation circuit 410. A high-frequency voltage depending upon the magnitude of the electrostatic capacity between the electrodes 401 and 4023 is outputted from the reception electrode 402. The high-frequency voltage outputted from the reception electrode 402 is converted into a DC voltage by a detection circuit 420. The presence or absence or the amount of a substance is determined based on the magnitude of the DC voltage produced in the detection circuit 420.

Description

technical field [0001] The present invention relates to a capacitive coupling sensor device and a substance detection method using the capacitive coupling sensor device. Background technique [0002] Among the sensor devices, there is a capacitive coupling type sensor device, that is, a capacitive coupling type (capacitance type) sensor device using a capacitor (capacitor). Japanese Unexamined Patent Application Publication No. 2000-80703 discloses an invention in which a capacitive coupling type sensor device is used to detect that a human body is seated on a toilet seat of a body part washing type. In the invention described in this publication, in addition to a detection electrode and a ground electrode for capacitive coupling, the sensor section is constituted by a guard electrode provided between the two electrodes, and the electrodes are insulated from each other. Then, the oscillation frequency in the high-frequency oscillation circuit is set using the electrostatic ...

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Problems solved by technology

[0003] However, in the device described in the above publication, the output signal obtained is not a general output signal like the so-called change in frequency, so there is a problem that a special device for detecting the frequency is required.

In addition, in the device described in the above publication, only the presence or absence of the substance of the human body is detected, and there is no attempt to detect the capacitance of the substance in a continuously variable manner like, for example, the capacitance change of a liquid.

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