An electrostatic stray field of a capacitive

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Unformatted text preview: c GmbH & Co. KG • FP 1110 5. Capacitive proximity sensors 5.1 Function description The operational principle of a capacitive proximity sensor is based on the measurement of the change of electrical capacitance of a capacitator in a RC resonant circuit with the approach of any material. An electrostatic stray field of a capacitive proximity sensor is created between an "active" electrode and an earth electrode. Usually, a compensating electrode is also present which compensates for any influence of the proximity sensor through humidity. 6 Oscillator (1) Switching status display (4) Internal constant voltage supply (7) Demodulator (2) Output stage with protective circuit (5) Active zone (capacitor) (8) Triggering stage (3) External voltage (6) Switching output (9) Fig. 5.1.1: Block circuit diagram of a capacitive proximity sensor If an object or medium (metal, plastic, glass, wood, water) is introduced into the active switching zone, then the capacitance of the resonant circuit is altered. This change in capacitance essentially depends on the following parameters: • The distance of the medium fr...
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This note was uploaded on 11/01/2012 for the course CHEMICAL 102 taught by Professor Jamesrodriguez during the Spring '12 term at Universidad Politécnica de Cartagena.

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