What are proximity sensors & their working principle

By | July 5, 2020

As the sensor name suggests, the Proximity sensor is a sensor that can detect other objects, which comes closer to it, up to a certain range of distance without any physical connection. The covering distance of sensor is called sensing range which varies according to size of the sensor, for example, an 18mm diameter inductive sensor will have a sensing range for 5mm to 8mm. See the datasheet here.

The maximum distance at which a sensor can sense other objects is called a nominal range, which also depends on the size of sensors. There are some sensors for which you can adjust their sensing and nominal ranges. You can see here how an adjustable proximity sensor works. A proximity sensor is a highly reliable and long functional life because of no mechanical parts and no physical contact between the sensor and sensed object.

How it works

Proximity sensor emits electromagnetic field or a ray of electromagnetic radiations, infrared, for instance, and wait for changes in these radiations or bounce back signals. The object which is sensed by a proximity sensor is often called the sensor’s target object. The target demand for different proximity sensors is different. For example , a capacitive proximity sensor or photoelectric sensor often demands a plastic target that is more suitable for them and an inductive proximity sensor always wants a metal object as sensor’s target.

what is proximity sensor

Proximity sensor types

There are different types of proximity sensors but mainly are two by which they known.

  1. Inductive type
  2. Capacitive type

Inductive type can detect metal objects and capacitive type can detect any object which comes closer to them. If you want to check other types you can view this link.

Proximity sensor applications

Proximity sensors have huge applications across every technological field. They finds application in industrial and manufacturing areas. They sense material and then respond to some type of action or simply tell about the presence or absence of that material. The most important feature of these sensors is that they don’t require physical connection with their target which is being sensed. That is why they are often called non-contact sensors.

Every type of sensor has its own technique of use for a specific operation in any device. Here I will tell you about the applications of proximity sensors in android and IOS.

How it works in mobile

I hope now you are known by this fact that proximity sensor works when anything comes close to it.

Large touch screen displays use huge battery power. So it should be turned off while it is not in use like calling someone or when the phone is in the pocket. In that case proximity sensors turn off your mobile screen, as in both cases mobile screen is close to your ear/cheeks or body in the pocket. In such cases, the proximity sensor activates sense objects and send a signal to the mobile processor to turn off the display.

There are some other techniques that are used for proximity sensing like detecting the change in capacitance, inductance, magnetic field, or even techniques like sonar. But, I doubt if they are used in cell phones. Thank you for your reading.

Please feel free to ask me anything about it.  

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