Inductive sensor

Non-metallic substances, such as liquids or some kinds of dirt, do not interact with the magnetic field, so an inductive sensor can operate in wet or dirty conditions.

The coil may have a ferromagnetic core to make the magnetic field more intense and to increase the sensitivity of the device.

Another form of inductive sensor uses one coil to produce a changing magnetic field, and a second coil (or other device) to sense the changes in the magnetic field produced by an object, for example, due to eddy currents induced in a metal object.

Most often this is physically a number of turns of insulated magnet wire wound around a high magnetic permeability core, such as a ferrite ceramic rod or coil form, and the winding may or may not have a feedback tap some number of turns from one end of the total winding.

In conjunction with a voltage or current gain device like a transistor or operational amplifier, this forms a tuned frequency oscillator.

Common applications of inductive sensors include metal detectors, traffic lights, car washes, and a host of automated industrial processes.

Because the sensor does not require physical contact it is particularly useful for applications where access presents challenges or where dirt is prevalent.