Inductive Proximity Sensor Principle of Operation

Written by: Jeff Himes

An inductive proximity sensor is a non-contact device that is used to detect a metal target.  When power is applied to an inductive proximity sensor the sensor’s coil will generate an oscillating electromagnetic field out of the face of the sensor.  This field will vary in shape and size depending on the diameter of the sensor and whether the sensor is a shielded or non-shielded model.  For example, a M12 size sensor will generate a smaller electromagnetic field than an M30 size sensor.   When the metal target gets close enough to the sensor’s face it begins to penetrate the electromagnetic field.  When this happens, eddy currents are generated on the surface of the metal target.  As the metal target gets closer to the sensor face – the eddy currents increase – which in turn decrease the amplitude of the electromagnetic field.  Once the electromagnetic field’s amplitude is reduced to a certain level – the sensor will activate indicating it has detected the metal target.

This explanation is a little wordy and, as in most cases, a visual demonstration can be of great help.  Watch this short video explaining the basic functionality of an inductive proximity sensor.

For more information on inductive proximity sensors, click here.