Capacitive Proximity Sensors:

Farnell offers commercial proximity sensors with detection ranges from 2 mm to 25 mm. These sensors are available in various output options and configurations, such as PNP and NPN, with supply voltages ranging from 2 V DC to 250 V DC and operating temperatures between -25°C and 80°C.

Capacitive proximity sensors are non-contact devices that work with both conducting and insulating (dielectric) objects, such as the unprepared surface of a mechanism or a moving conveyorized object. These sensors contain a high-frequency oscillator and a sensing surface formed by two metal electrodes. When the target approaches the sensing surface, it enters the electrostatic field of the electrodes and alters the oscillator's capacitance. Consequently, the oscillator circuit begins oscillating and changes the sensor's output state upon reaching a specific amplitude. As the target moves away from the sensor, the oscillator's amplitude decreases, returning the sensor to its original state. 

Capacitive proximity sensors can detect metal objects as well as non-metallic materials such as paper, glass, liquids, and cloth.  To learn more about proximity sensors for industrial applications, please read our comprehensive guide for proximity sensors.