Autonics Capacitive Sensors

Capacitive proximity sensors are capable of detecting any material with dielectric different from air. The sensors can detect conductive and non-conductive materials including metal, iron, stone, plastic, water, and grain. Some models come with built-in sensitivity adjuster allows easy configuration of detecting distance, making it ideal for application in various environmental settings.

Capacitive sensors have the ability to adjust the sensitivity or the threshold level of the oscillator. The sensitivity adjustment can be made by adjusting a potentiometer, using an integral teach pushbutton or remotely by using a teach wire. If the sensor does not have an adjustment method then the sensor must physically be moved for sensing the target correctly. Increasing the sensitivity causes a greater operating distance to the target. Large increases in sensitivity can cause the sensor to be influenced by temperature, humidity, and dirt.

Principle of operation

A capacitive sensor acts like a simple capacitor. A metal plate in the sensing face of the sensor is electrically connected to an internal oscillator circuit and the target to be sensed acts as the second plate of the capacitor. Unlike an inductive sensor that produces an electromagnetic field a capacitive sensor produces an electrostatic field.

The external capacitance between the target and the internal sensor plate forms a part of the feedback capacitance in the oscillator circuit. As the target approaches the sensors face the oscillations increase until they reach a threshold level and activate the output.

Capacitive sensors have the ability to adjust the sensitivity or the threshold level of the oscillator. The sensitivity adjustment can be made by adjusting a potentiometer, using an integral teach pushbutton or remotely by using a teach wire. If the sensor does not have an adjustment method then the sensor must physically be moved for sensing the target correctly. Increasing the sensitivity causes a greater operating distance to the target. Large increases in sensitivity can cause the sensor to be influenced by temperature, humidity, and dirt.