4mm Inductive Proximity Sensors:

element14 offers a wide range of inductive proximity sensors with detection ranges from 0.6mm to 30 m. They are available in different output options and configurations, such as PNP and N. 

An inductive proximity sensor is based on the change of induction due to the motion of a metallic object in a magnetic field. An inductive proximity sensor consists of oscillators, demodulators, and level and switching amplifiers. If a metallic object enters the electromagnetic field of the oscillator coil, eddy currents are induced in this coil, which changes the amplitude of the oscillation. The demodulator converts the change in the amplitude to a DC signal, causing the trigger stage to trip and the semiconductor outpage stage to switch.

Inductive proximity sensors detect ferrous and nonferrous metals such as copper, aluminum, and brass). They are used in electromagnetic clutches and valves, as actuators in machine tool carriage, pneumatic cylinders, etc.  

To learn more about proximity sensors for industrial applications, please read our comprehensive guide for proximity sensors.