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What is a Proximity Sensor? How it Works? Types Advantages,Disadvantages &Applications

This blog covers the basics of proximity sensors, its working, applications, and advantages and disadvantages.

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What are Proximity sensors? Overview

A proximity sensor is a non-contact sensor that detects the presence of an object (also known as the “target”) when it enters the sensor’s field of view. The sensor may detect a target via sound, light, infrared radiation (IR), or electromagnetic fields, depending on the type of proximity sensor. Phones, recycling factories, self-driving cars, anti-aircraft systems, and assembly lines all employ proximity sensors. There are different types of proximity sensors, and each detects targets in a different way. The inductive proximity sensor and the capacitive proximity sensor are the two most often used proximity sensors.

Proximity sensors detect the movement or presence of objects without making physical touch and transmit the information in the form of an electrical signal. It can also be referred to as a proximity switch, which is a term used by the Japanese Industrial Standards (JIS) to describe all contactless sensing devices.

Where are Proximity Sensors used?

Proximity Sensors are widely employed in industrial and manufacturing applications, particularly in the areas of safety and inventory management. It is used for object identification, placement, inspection, and counting in an automated production line, for example. It’s also utilised in an industrial conveyor system to detect parts.

Proximity sensors are also used in consumer electronics. Proximity sensors in smartphones determine if a user is holding their phone close to their face. They’re also employed in consumer electronics as capacitive touch switches.

Features of Proximity Sensor:

  • Non Contact Detection

Unlike a limit switch, it detects an object without any mechanical contact. Hence, there is no likelihood of the sensing object or the sensor getting damaged by contact.

  • Usable in severe environment

Reliable sensing is possible even in adverse conditions where it can come in contact with water, etc. Most of the sensors have IP67 protection and oil resistant construction.

  • High precision

It is suitable for precise object positioning because of its very high repeatability.

  • Short response time

Stable detection is possible even with fast traveling objects because of its high response frequency (3.3 kHz max.).

  • Long life

Due to its non-contact output, it has a long life and requires practically no maintenance.

  • Short sensing range

Although there are several methods for improving the sensing range, such as increasing the detection coil size, using non-shielded sensor heads, etc., the sensing range is still smaller than that of photoelectric sensors.

  • Only metal detection

It cannot detect non-metals in which current cannot flow, since detection is based on thermal loss due to induced current.

(Also, metals such as ferrite, which do not allow current flow, cannot be detected.)

Types of Proximity Sensor:

According with the non contact object detection method, there are five types of proximity sensor. They are,

  1. Inductive Proximity Sensor.
  2. Optical Proximity Sensor.
  3. Capacitive Proximity Sensor.
  4. Magnetic Proximity Sensor.
  5. Ultrasonic proximity Sensor.

An inductive proximity sensor can only detect metal targets. This is because the sensor utilizes an electromagnetic field. When a metal target enters the electromagnetic field, the inductive characteristics of the metal change the field’s properties, thereby alerting the proximity sensor of the presence of a metallic target. Depending on how inductive the metal is, the target can be detected at either a greater or shorter distance.

Capacitive proximity sensors, on the other hand, are not limited to metallic targets. These proximity sensors are capable of detecting anything that can carry an electrical charge. Capacitive sensors are commonly used in liquid-level detection. Possible targets for capacitive sensors include but are but not limited to: glass, plastic, water, wood, metals, and a myriad of targets of other materials.

Another type of proximity sensor is called a photoelectric proximity sensor. There are two main types of photoelectric proximity sensors: reflective and through-beam. Reflective proximity sensors detect objects when the light emitted from the sensor is reflected back at the photoelectric receiver. Through-beam sensors detect targets when the target breaks the beam of light between the sensor’s emitter and receiver. 

Two other commonly used proximity sensors are the magnetic proximity sensors and ultrasonic proximity sensors. Magnetic proximity sensors are only used to detect permanent magnets. Ultrasonic proximity sensors emit a high pitch sound. The distance between the sensor and the target is determined by how long the sound takes to reflect back to the sensor.

Working principle of a proximity sensor

When a target enters the field of a non-contact sensor, such as a proximity sensor, it recognises its presence. The detection of a target can be done via light, sound, infrared, or electromagnetic fields, depending on the type of sensor.

Recycling facilities, phones, anti-aircraft systems, assembly lines, and self-driving automobiles all use these types of sensors. There are various types of proximity sensors available, each of which detects targets in a different way.

Advantages of proximity sensor:

  • It can detect both metallic and nonmetallic targets.
  • It has good stability.
  • High speed provided.
  • High switching rate.
  • Work in harsh environmental conditions.
  • Low cost and power consumption.
  • A capacitive sensor is good in terms of power usage.
  • They are useful and can help with many security problems.

Disadvantages of proximity sensor:

  • They are affected by temperature and humidity.
  • Difficulties in designing.
  • The operating range may be limited.
  • A capacitive proximity sensor is not as accurate to compare to the inductive sensors.
  • It detects only the metallic target.
  • They can be easily set off and cause a problem.
  • They are expensive than inductive and capacitive sensors.

Proximity Sensor Applications

Proximity sensors can be used in a range of environments and for many different applications. They are beneficial to any application where it is necessary to detect an object in a defined range. This could include:

  • Standard object position detection
  • Transportation, logistics, and supply chain
  • Inspection and quality assurance
  • Process control
  • Level detection
  • Food processing and manufacturing
  • Agriculture

They can also be employed in situations with oil or water, giving them a significant advantage over other detection technologies. Depending on the dielectric constant of the object, capacitive proximity sensors can detect media such as water, glue, and metal. As explained below, different types of sensors are better suited for detecting different objects:

  • Capacitive proximity sensors – metals, liquids, water, resin, powders
  • Inductive proximity sensors – metals including aluminium, copper, brass, and iron
  • Magnetic proximity sensors – magnets

Proximity sensors are also appropriate for usage in areas where temperatures fluctuate or where high temperatures are widespread. Although temperature compatibility varies by model, proximity sensors may generally be utilised in temperatures ranging from -50 to 100 degrees Celsius.

Hope this blog helps you to understand basics of magnetic proximity sensors, its working, applications, and advantages and disadvantages.We ,MATHA ELECTRONICS  will come back with more informative blogs.

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