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Table of contents
What are Infrared Sensors?
Working on Infrared Sensors
Types of IR Sensor
Active IR Sensor
Passive Infrared Sensor
Quantum Infrared Sensor
Application of IR Sensor
Frequently Asked Questions
What are infrared sensors? 
Write one tangible example of infrared sensors?
What are the advantages of infrared sensors?
What are the disadvantages of infrared sensors?
Last Updated: Mar 27, 2024

Infrared Sensors

Author Saumya Gupta
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The importance of data has significantly increased, with many experts saying “data is the new oil.” Sensors are devices that detect superficial data, replacing it with a signal that humans and machines can differentiate.

Sensors made it viable to gather information in almost any situation and are now used in medical care, nursing care, industrial, logistics, transportation, agriculture, disaster prevention, tourism, regional businesses, etc. With the expansion of the fields in which sensors play an essential role, the market is still growing with various sensors.

                                                                   Infrared camera

                                                                   Source: Allied 

This article will discuss infrared sensors and their characteristics, how they support IoT ( Internet of things), and relevant information.

What are Infrared Sensors?

An infrared sensor is an electronic gadget used to compute and detect infrared radiation in its nearby domain. Infrared radiation, also known as infrared light - refers to electromagnetic radiation with wavelengths longer than visible light. It is said to surround wavelengths from around 1 millimeter to approximately 700 nanometers (the theoretical red edge of the clear spectrum). It is thus discreet to the human eye but can be discovered as a commotion of heat on the skin.

Infrared radiation (IR) was fortuitously discovered by the astronomer William Herschel in 1800. As he deliberated the temperature of each color of the light (separated by a prism), Herschel observed that the temperature just past the red light was the highest. It is prime to note that although the infrared wavelength is longer than that of visible light, it is very much on the same electromagnetic spectrum. Anything that sends out heat has a temperature above five degrees Kelvin and gives off infrared radiation.

An infrared sensor is a radiation-sensitive optoelectronic device with spectral sensitivity in the infrared wavelength range of 780 nm to 50 µm. IR sensors are used in motion detectors, building services to switch on lamps, or alarm systems to detect unwelcome guests. The sensor elements detect the heat radiation (infrared radiation) that occurs over time and space due to the movement of people. Infrared sensors meet relatively low requirements and are affordable, mass-produced items. InfraTech develops, produces, and sells pyroelectric detectors.

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Working on Infrared Sensors

An infrared sensor's working fundamental is similar to the object detection sensor. This sensor includes an IR LED and an IR Photodiode, so combining these two can form a photo-coupler or optocoupler. The physics laws used in this sensor are planks radiation, Stephan Boltzmann & weins displacement.

An infrared LED is a transmitter that releases IR radiation. This LED looks like a standard LED, and the radiation caused by this is not evident to the human eye. Infrared receivers mainly detect the radiation regulating an infrared transmitter. These infrared receivers are obtainable in photodiode form. IR Photodiodes are dissimilar to standard photodiodes because they see IR radiation. Different kinds of infrared receivers mainly exist depending on the voltage, wavelength, package, etc.

                                                                             Source: electricalfunda

It is used to combine an IR transmitter & receiver. The receiver's wavelength must equal the transmitter. The transmitter is an IR LED, whereas the receiver is an IR photodiode. The infrared photodiode is responsive to the infrared light caused via an infrared LED. The resistance of the photodiode and the change in resulting voltage is in proportion to the infrared light obtained. The above paragraph depicts the  IR sensor's fundamental working principle.

Once the infrared transmitter generates emission when it arrives at the object & some of the emission will reflect toward the infrared receiver end. The sensor result can be decided by the IR receiver depending on the intensity of the response.

Types of IR Sensor

The classification of IR sensors can be done based on the application, including the following.

Active IR Sensor

This type of sensor includes both the emitter & the receiver, which are also known as transmitter & receiver. A laser diode or LED is used as a source in most situations. LED is used for non-imaging infrared sensors, whereas laser diode is used for infrared imaging.

The working of an infrared sensor can be done through radiating energy, detected and received through the detector. Further, it is processed through a signal processor to fetch the required data. The best examples of active infrared sensors are reflectance & break beam sensors.

Passive Infrared Sensor

Passive Infrared Sensor (PIR) includes detectors only, and this kind of sensor uses targets like infrared transmitters or sources. Here, the object will radiate the energy & detects it through infrared receivers. After that, a signal processor is used to understand the signal to obtain the required data.

The best examples of PIR sensors are bolometers, Pyro-Electric detectors, Thermocouple-Thermopile, etc. 

PIR sensors are available in two types: thermal IR and quantum IR.

These sensors are independent of wavelength and utilize heat-like energy sources. These are slow along with the response time as well as detection time.

Quantum Infrared Sensor

These types of sensors depend on wavelengths and the response time and detection time they have are high. These kinds of infrared sensors need repeated cooling for exact measurement.

Application of IR Sensor

The use of infrared sensors to precisely measure the chemical composition of materials or gases in military applications is well known. With their rapidly declining price tag, these IR sensors are gaining traction in IoT M2M applications, including medical diagnostics, imaging, industrial process controls, fire detection, remote gas leak detection, pollution monitoring, and real-time combustion control.

Some of the essential mechanisms for preserving a clean, secure, and healthy environment are sensors, sensor systems, and sensor networks that detect and appraise the quantity of particular chemical trace gases. Once the origin is located, monitoring also provided by sensors supports mitigation and compliances.

 Source: electricalfunda 

IR sensors are also valid for industrial processes and automotive monitoring and health, especially breath analysis. Today's standard expensive and cumbersome medical tests will give way to breathalyzers to diagnose medical conditions immediately. Medical care will become more dynamic and remote care more exact for today's society.

Infrared vision has various uses. It can envision heat discharge in homes, help doctors keep an eye on blood flow, identify environmental chemicals in the environment, allow art historians to see under layers of paint, and integrate it with contact lenses or wearable electronics.

Frequently Asked Questions

What are infrared sensors? 

The Infrared sensor is a device that uses infrared waves to sense the characteristics of surroundings.

Write one tangible example of infrared sensors?

Televisions, for example, use an infrared detector to interpret the signals sent from a remote control.

What are the advantages of infrared sensors?

  • Secure communication
  • Long-lasting battery life
  • Small size and affordable
  • Good stability
  • Fast response time

What are the disadvantages of infrared sensors?

  • Infrared radiation is harmful to the eyes.
  • Shorter-Range
  • Control one device at a time
  • Lower data rate transmission
  • Affected by hard objects 


This article extensively discusses Infrared sensors and their purpose. We have also discussed the working, characteristics, advantages, and disadvantages of Infrared sensors.

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