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A Complete Guide to Proximity Sensors

As their name suggests, proximity sensors are instruments that are used to detect the presence of an object without the need for physical contact. Using various methods, they can check for the presence of an object based on how it interacts with a projected field. As a result of this capability, the sensors are commonly employed in parking lots, mobile phones, conveyor systems, and more. Additionally, they come in several major types, including the magnetic, capacitance, photoelectric, and ultrasonic variations.

Four Major Types of Proximity Sensors - 

Inductive Proximity Sensor

Inductive sensors work under the electric principle of inductance, meaning that they create an electro-motive force by generating a moving magnetic field around an electric conductor, or conversely, by moving an electric conductor through a static magnetic field. In this case, the sensor uses an inductive coil to detect the presence of metallic objects. As such, they are often used to detect the movement of machines, such as forklifts and hydraulic actuators, in industrial environments.

Capacitive Sensor

These sensors detect metallic and nonmetallic objects in liquid, solid, and granulated forms by observing capacitance, or the capability of a material object or device to store electric charge. The device operates as an open capacitor as it incorporates two conduction locations positioned at the sensing head. The capacitance of these two plates changes when an object enters the sensing area.

Photoelectric Sensor

Photoelectric sensors are highly accurate and can sense a target that is less than 1 mm in diameter. Using a laser diode and a photodiode receiver, they can detect an object based on whether the light beam is interrupted. In addition, supporting electronics are designed to amplify the receiver so that it is highly sensitive and capable of observing faint changes in the transmitted beam of visible or infrared light. Within this category, there are two main types: through-beam and retro-reflective sensors.

Through-Beam: Through-beam sensors are a specific type of photoelectric sensor that provides a constant beam of light from an emitter to a receiver. Whenever an object passes between the two devices, it breaks the beam, creating an instantaneous response. These sensors are reliable to use and may be found in both commercial and industrial areas.

Retro-Reflective: Having the longest photoelectric sensing distance, retro-reflective sensors monitor a range of up to 10 meters. They work by incorporating through beam sensors, but the emitter and receiver are located in the same housing, facing the same direction. Within the device, the emitter produces a laser and projects it towards the reflector, which deflects a beam back to the receiver. This orientation ultimately saves on cost and time spent, but may not be appropriate for detecting reflective objects that can trick the receiver.

Ultrasonic Sensor

Ultrasonic sensors consist of three components: a transmitter, receiver, and trans receiver. When in operation, the transmitter converts an electrical signal into an ultrasound, followed by the receiver working to convert the ultrasound into an electrical signal. From here, the trans receiver then functions to transmit and receive the ultrasound. In addition to sensing objects, these sensors can also be used to measure a tank’s fluid level by measuring the distance of entry to the surface of the fluid. To do this, ultrasonic sensors determine a specified sensing distance by measuring propagation time, otherwise known as the amount of time it takes for a signal to reach its destination. This sensor is best suited for applications that require detection of a continuous object.


Overall, proximity sensors provide a way to sense the presence of objects using light beams, magnetic fields, and other techniques. If you are on the lookout for proximity sensors and other industrial components, Aerospace Domain is ready to support you with your fulfillment needs. As a leading distributor of industrial, defense, aviation, and electronic components, we provide a wide selection of quality-sourced items to choose from. Begin procuring the parts you need from our team of market experts when you submit a Request for Quote (RFQ) form on any item(s) of interest. With representatives on standby 24/7x365, you can expect a custom solution to your parts needs in 15 minutes or less!


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