Level Sensing 

A proximity sensor is a sensor which detects the presence of nearby objects without any physical contact. This can be done using the electromagnetic field or electromagnetic radiation beam in which the field or return signal changes in the event of the presence of any object in its surrounding. Proximity Sensors detect an object without touching it and therefore, they do not cause abrasion or damage to the object. The devices such as limit switches detect an object by contacting it, but Proximity Sensors are able to detect the presence of the object electrically, without any touch.