sensors for proximity monitoring are devices that detect objects nearby, or within a set radius, without physical contact up to a nominal range or sensor vicinity. when an object – either person or equipment – enters into the determined range of the sensor, the associated method of detection will record the activity and send data back to the sensor, warning devices or platforms. ato proximity sensor is a common technology used for vehicle proximity sensing including infrared, radio frequencies, bluetooth and specialized lasers. the 120v, m8, 2 wire proximity sensors have the largest sales volumes. they include an oscillating circuit that generates an electromagnetic field. any metal part that approaches it is detected because it becomes the seat of induced currents and then reduces oscillations, which the detector notices. the 4 mm, npn proximity sensor is similar to that of inductive sensors. an electromagnetic field is generated by a capacitor located on the main site of the sensor. a nearby part changes the intensity and frequency of oscillations. unlike inductive sensors, capacitive sensors do not only detect metal parts but parts of all shapes and materials (solid, liquid, viscous, powdery, etc.). the 10mm ring type inductive proximity sensor is a high-quality proximity sensor at an affordable price, npn/ pnp/ 2 wire three output types for selection, embedded type installation, > 20mω insulation resistance and repeated accuracy ≤5%. these kinds of ato proximity sensors have a significant market share. it is based on an optical principle. it detects the object when the light beam is either reduced or interrupted by the object passing through it. depending on the object passing through the light beam and the detection distance, different configurations are possible.