Introduction
An inductive sensor is a proximity sensor that detects ferromagnetic objects, such as steel or iron.
How it works
- the sensor has a wound coil next to a permanent magnet, in a housing
- when nothing moves, the flux lines do not move, so no voltage is induced in the coil
- when a ferromagnetic object enters or leaves the magnetic field, the inductance changes
- the change in flux induces a voltage pulse in the coil. Its amplitude and shape are proportional to the rate of change of the flux
- the voltage at the coil output tells you that an object is near
Limitation
The sensitivity falls quickly as the distance increases. The sensor works only at distances of fractions of a millimetre.