Wednesday, January 20, 2016



Infrared Light that is invisible to the human eye, INFRARED SENSOR detect the infrared frequency(Light) , and make the work done.
In daily life we use many IR INSTRUMENTS 



DAFINATION :- 1. An infrared sensor is an electronic instrument which is used to sense certain characteristics of its surroundings by either emitting and/or detecting infrared radiation. Infrared sensors are also capable of measuring the heat being emitted by an object and detecting motion. Infrared Radiation.

2. An infrared sensor is a device that emits and/or receives infrared waves in the form of heat. While most infrared sensors transmit and receive infrared waves, some can only receive them. These types of infrared sensors are known as Passive Infrared Sensors (PIR sensors) or motion detectors.


Sensors are used to measure physical quantities such as temperature, light, pressure, sound, and humidity. They send signals to the processor. For example: A security alarm system may have an infrared sensor which sends a signal when the beam is broken. 

  Working of IR sensor

Principles of Operation

We have already discussed how a light sensor works. IR Sensors work by using a specific light sensor to detect a select light wavelength in the Infra-Red (IR) spectrum. By using an LED which produces light at the same wavelength as what the sensor is looking for, you can look at the intensity of the received light. When an object is close to the sensor, the light from the LED bounces off the object and into the light sensor. This results in a large jump in the intensity, which we already know can be detected using a threshold.
Depiction of the operation
of an IR Sensor

What is an Infrared Detector?

An infrared detector is a pyroelectric sensor that detects the light spectrum’s infrared wavelength. Infrared detectors are usually emitters as well, but this is not always the case. Infrared detectors can be made of a phototransistor, photodiode, or photoresistor as these are basically the same device. Infrared detectors have many uses and are essential to the transference of infrared light.

Advantages And Applications :-

Infrared sensors are used in a wide variety of applications.

-> Television Remotes emit infrared light in order to change channels

-> Infrared Detectors can detect infrared light from far distances over a large area

-> Infrared Detectors operate in real-time and detect movement, making them ideal for security purpose

-> Infrared sensors are also used as motion detectors i.e. Movement of people, animals, and moving objects

-> They are also used in night-vision applications, laser range finding, and heat-seeking missiles.

Radiation Thermometers

IR sensors are used in radiation thermometers to measure the temperature depend upon the temperature and the material of the object and these thermometers have some of the following features
  • Measurement without direct contact with the object
  • Faster response
  • Easy pattern measurements
-> Flame Monitors

These types of devices are used for detecting the light emitted from the flames and to monitor how the flames are burning. The Light emitted from flames extend from UV to IR region types. PbS, PbSe, Two-color detector, pyro electric detector are some of the commonly employed detector used in flame monitors.

-> The speed sensor is used for synchronizing the speed of multiple motors. The temperature sensor is used for industrial temperature control. PIR sensor is used for automatic door opening system and  Ultrasonic sensor are used for distance measurement.


Although infrared sensors have many advantages, they also have several disadvantages.

 -> They are incapable of distinguishing between objects that irradiate similar thermal energy levels. 

-> Infrared detectors are also rather expensive, so they are not as widely used as they could be.




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