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Capacitive Proximity Sensors

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Capacitive Proximity Sensors: Capacitive Sensors are very similar to inductive proximity sensors in shape and function. The difference is that the capacitive sensor can sense not only conductors/metallic but also nonconductors. Capacitive sensors are sensitive to all materials. Just like an ultrasonic sensors that is used as a limit switch, it can sense any substance, metallic or non-metallic close by. The sensing distance is dependent on the material but, at best it should not be expected to be more than 20 cm.

Description: Capacitive proximity sensor is non-contact sensing solution to metallic as well as non-metallic objects. With adjustable sensitivity almost any medium can be detected with desired reliability.

Design and Principal: The primary functional element of capacitive proximity switch is high frequency oscillator with floating electrode in the transistor base circuit. In non-activated state, noise field exists in region of base electrode which represents active area of proximity switch. When medium appears in active area, oscillations begin. The switching stage rectifies and switches high frequency oscillations, resulting DC signal triggers output stage. Switching stage includes signal feedback system, level of which can be adjusted by potentiometer, thus providing presentable response sensitivity of switch.



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