We developed a proximity sensor using coil windings to detect the magnetic field. When magnet or magnetic objects come near to the sensor, it changes the output signal of the sensor.
Coil based proximity sensors are popular because they can be easily made and sensitive to magnetic fields.These sensor are widely used in automation systems, vehicle detection, and industrial machinery etc.

Proximity sensor installed at field

Block diagram of Proximity Sensor.

Block diagram shows a proximity sensor with a coil winding as its sensing element, these sensor output is connected to a 3 pin connector.
the first pin supplies 24V power to the sensor, second pin is sensor signal its either active low or active high, and third pin is ground .