Proximity Sensors

Proximity sensors are non-contact devices that detect the presence or absence of an object using light, sound or electromagnetic fields and transmit that information into an electrical signal. They can be used in industrial and manufacturing industries for inventory management and safety applications. In automated production lines, proximity sensors can be used for object detecting, inspecting, counting and positioning. Four commonly used types of proximity sensors are: ultrasonic, inductive, capacitive and photoelectric.

Ultrasonic proximity sensors consist of an ultrasonic transmitter and an ultrasonic receiver. The transmitter emits a high-frequency sound wave which, when it strikes the object, reflects back to the receiver. The distance of the object is calculated based on how long it took for the sound wave to travel back to the receiver. Ultrasonic proximity sensors can detect solid, liquid and granular objects.

Inductive proximity sensors utilize an electromagnetic field to detect the presence of metallic objects. When a metallic object enters the electromagnetic field, the inductive characteristics of the metal changes the field’s properties, alerting the sensor of the object’s presence. Inductive proximity sensors can only detect metallic objects.

Capacitive proximity sensors utilize the electrical property of capacitance and the change of capacitance in the electrical field around the face of the sensor to detect the presence of an object. They can detect solid, liquid or granular objects.

Photoelectric sensors are devices that use visible or infrared light to detect the presence of an object or its distance from the sensor. Photoelectric sensors consist of an emitter that sends the light and a receiver that receives the light. When the emitted light is interrupted or reflected by an object, it alters the amount of light that arrives at the receiver.