An infrared (IR) sensor is an electrical gadget that detects and measures infrared radiation in its surroundings. It was discovered in 1800 by accident by William hatchel. He found that the temperature just beyond the red light was the highest while measuring each hue of light (separated by a prism). Additionally, because the wavelength of IR is longer than that of visible light, it is invisible to the human eye (though it is still on the same electromagnetic spectrum). Therefore, Infrared radiation is emitted by everything that emits heat (anything with a temperature over roughly five degrees Kelvin).
IR sensors are categorized into two types. These include the active and passive IR sensors. Infrared radiation is emitted and detected by active infrared sensors. A light-emitting diode (LED) and a receiver make up active infrared sensors. When an object approaches the sensor, the LED’s infrared light reflects it and is recognized by the receiver. Active infrared sensors are often utilized in obstacle detection systems as proximity sensors (such as in robots)
Passive infrared (PIR) sensors do not emit infrared radiation; they detect it. Passive infrared sensors are made up of the following components; two pyroelectric material strips. Secondly, an infrared filter is a device that allows you to see infrared (that blocks out all other wavelengths of light).additionally, a Fresnel lens is a type of camera lens (which collects light from many angles into a single point). Finally, it has a housing unit (to protect the sensor from other environmental variables, such as humidity).
PIR sensors are frequently employed in motion-based detection systems, such as home security systems. The difference in IR levels between the two pyroelectric elements is monitored when a moving object that emits infrared radiation approaches the sensing range of the detector. After that, the sensor sends an electronic signal to an embedded computer, which sets off an alarm.
Listed below are some of the advantages of IR sensors.
- Because of the line of sight or point-to-point style of communication, it ensures secure communication.
- Because of the decreased power consumption, the battery in infrared gadgets lasts a long time.
- Infrared motion sensors reliably detect movements both during the day and at night.
- The sensor does not need to be in contact with the product to detect it. The infrared gadgets are better for targets that are in the dark.
- Soft objects that are difficult to detect with ultrasound can be measured with infrared instruments.
- They are physically smaller and more cost-effective.
- It has a faster response time than a thermocouple.
- It has a high level of long-term stability.
- The precision of the infrared sensor is unaffected by corrosion or oxidation.
- It has a high level of repeatability.
Some disadvantages include;
- Hard things (e.g., walls, doors), smoke, dust, fog, sunlight, and other factors alter infrared frequencies. As a result, it cannot pass through walls or doors.
- High-powered infrared rays can cause eye injury.
- It can only control one device at a time in the monitor and control application. Furthermore, managing items that are not in LOS is challenging (Line of Sight). Therefore, to communicate, the transmitter and receiver must have a clear line of sight.
- It only supports a small range; therefore, performance diminishes over more considerable distances.
- When compared to wire transmission, it allows for a lower data rate.
Factors to consider when buying infrared thermal sensors
1. Wavelength
When measuring temperature, wavelength is a critical factor to consider. The emissivity of the target item, which measures the effectiveness of the infrared radiation emitted by the surface, directly impacts the wavelength selection in an infrared sensor. When radiated energy is measured at different wavelengths, the emissivity of an item varies. Further, Adjustable emissivity correction is a feature of infrared sensors that allows for accurate temperature reading in various circumstances. As a result, the wavelength band of an infrared temperature sensor should be known while choosing one. In addition, the values of object emissivity must be determined and documented throughout a wide temperature and wavelength range.
2. Temperature range
Non-contact infrared sensors can detect temperatures as very low and very high. Infrared sensors specific to these conditions are available, for instance, if the measurement is required in chilling chains, laboratories, or even hot melting materials or blast furnaces. As a result, users should be aware of the necessary measures. As a result, users should have a thorough understanding of the needed measuring range before selecting the best option for their application. If the requirement is to monitor start-up or cool-down temperatures in a process, a sensor with a wide temperature range must be chosen. Infrared sensors with a narrow sensor, on the other hand, can achieve higher output signal resolutions while monitoring and managing temperatures.
3. Response time
Infrared sensors with fast response times are necessary when sensing moving or rapidly heating things. Sensors with response times configurable down to 1 millisecond are also available on the market for these applications. On the other hand, fast sensors may exceed the capability of present control instruments in particular applications when there is a considerable thermal lag in heating a process.
4. Application type
Dirt, fumes, water vapor, noise, electromagnetic fields, and vibrations, among other things, can lead to measurement errors or even the lens of the sensor being destroyed. Temperature sensors with characteristics like protective housing, air purging, or water cooling should be sought since they can protect the sensor from the environment while still providing accurate results.
5. Size
The region to be measured with an infrared sensor must fill the field of vision of the instrument. Sensors with a lot of views that are 50% smaller than the measurement target are generally suggested. Additionally, the impact of sensors with field views that are either too large or too small than the target on temperature readings is the rationale for this choice. Huge targets do not measure temperature variation outside the measurement area. As a result, the sensor and the target must have a clear line of sight. Various infrared sensors are available for small or moving objects in and out of the field of view, depending on the target size.
