What are Proximity Sensors, How They Work And Types?

what are proximity sensors

These days technology is advancing everyday with some kind of new inventions. Today One company launches a product with any new technology, several other starts booming up with different option in that same technology.

These days we are hearing of and using various kinds of sensors in our life. I’m here not talking about Human’s five sense organs, here we are talking about sensors. Sensors are also known as detectors which converts physical quantity and converts it to a signal. There are many types of Sensors invented for different type of particular work. Today our subject is Proximity Sensors, we gonna talk here about what actually it is, how it works and its types.  So without wasting any time let’s checkout

How Proximity Sensors Work?

When anything comes in the range of Proximity sensor it flash out infrared beam and monitors reflections. When sensor senses reflections it confirms that there’s an object nearby.


An Inductive Proximity Sensor consists of an oscillator, a ferrite core with coil, a detector circuit, an output circuit, housing, and a cable or
connector. The oscillator generates a sine wave of a fixed frequency. This signal is used to drive the coil. The coil in conjunction with ferrite core induces a electromagnetic field. When the field lines are interrupted by a metal object, the oscillator voltage is reduced, proportional to the size and distance of the object from the coil. The reduction in the oscillator voltage is caused by eddy currents induced in the metal interrupting the field lines. This reduction in voltage of the oscillator is detected by the detecting circuit.

What are Proximity Sensors

We can say that proximity sensor is a device which detects objects nearby without any physical contact up to nominal range or sensor’s vicinity. In brief we can also say that Sensors which convert information on the movement or presence of an object into an electrical signal are called proximity sensors.

In this there’s one more term you need to learn and that is sensing object – the object being sensed is defined as sensing object.

Types of Proximity Sensors

There are several types of proximity sensor which are used according to the need, material detection and many other things. To classify them here are its types:

Inductive Proximity Sensors 

inductive proximity sensors

Device which generates output signal or electrical signal when metal objects are either inside or entering into its sensing area from any direction. The metal objects above includes iron, aluminum, brass, copper, etc with varied sensing distances.

inductive proximity sensor range

Other factors which affect Proximity sensors: flat targets are preferable,  targets larger than the sensing face may increase the sensing distance. First inductive proximity sensor was introduced in the mid 60’s. 

Capacitive Proximity Sensors

conductive proximity sensors

It can also detect metals but along with it can also detect resins, liquids, powders, etc. This sensor working can vary accordingly covering material, cable longness, noise senstivity. Its sensing distance also vary according to factors such as the temperature, the sensing object, surrounding objects, and the mounting distance between Sensors. Its maximum range of sensing is 25 mm.

Magnetic Proximity Sensors

magnetic proximity sensors

Name is saying its sensing object – magnets. Magnetic Proximity Sensors have no electrical noise effect and it can work on DC, AC, AC/DC, DC. Again sensing distance can vary due to factors such as the temperature, the sensing object, surrounding objects, and the mounting distance between Sensors. This type of sensors have highest sensing range upto 120 mm.

These sensors has been used in various devices like mobile phones, tablets, security appliances, etc. These days its mostly used on mobile phones in order to make it more functional, responsive and useful.

What you say? Share your views via comments.

Image Courtsey: Inotek, Omron

Sources: Omron, Altechcorp, Penton Media

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