Contactless infrared temperature sensors – fast, easy, reliable, and ultra-hygienic

What is an infrared temperature sensor?

Everything in the universe that has mass emits a certain amount of energy in the form of heat. An infrared (IR) temperature sensor uses the difference between infrared rays coming off of an object and the surrounding environment to determine the surface temperature of an object. Let’s take a closer look at how this works…

Light coming from an object in the form of IR rays is funnelled into an electronics detector that converts thermal energy into electrical energy – also known as a thermopile. Inside this thermopile, the IR radiation is turned into heat. This is then turned into electricity that can then be measured and displayed. All of this takes place within a few seconds. The voltage output is directly proportional to the heat flux through the thermal resistance layer. Thermopile output is generally just tens or hundreds of millivolts and no external power source is required.

The performance of these sensors can be greatly enhanced by introducing filters that help the thermopile remain dirt free and ensures only the desired IR radiation reaches the absorber. Silicon, which can’t be penetrated by visible light but is transparent to wavelengths longer than 2μm is generally used for the lens.

Contactless Infrared Temperature Sensor image
Example of an infrared image taken by a infrared temperature sensor

Infrared Temperature sensor measurement principles

Infrared temperature sensors are often based on one of the following two working principles. Both principles have strengths and weaknesses.

Measuring temperature using thermopile sensors

Thermopiles are used in a wide range of applications, from industrial pyrometers to climate control devices. They’re commonly found in portable devices such as tablets, smartphones and laptops, in which they measure the case temperature. Device performance is optimized on the basis of this key input. They’re good for reading moving objects and don’t wear out as contact isn’t required. 

One of the most common uses is as part of a temperature measuring device. These include everything from infrared thermometers used by medical professionals to thermal accelerometers to measure the temperature profile inside the sealed cavity of the sensor.

Measuring temperature using microbolometer cameras

An alternative popular method to measure temperature over larger distances is by using a ‘microbolometer’ as a detector in a thermal camera. Infrared radiation with wavelengths between 7.5–14 μm strikes the detector material, heating it and thereby changing its electrical resistance. This resistance change is measured and processed into temperatures that can be used to create an image.

Camera-based temperature sensors based on the microbolometer principle have a high pixel resolution and good signal to noise ratio. However to arrive at truly accurate measurements frequent image correction recalibration is required. Therefore, most commercial higher end systems use an (expensive) temperature reference source (a so-called ‘black body’) to frequently recalibrate. This makes the complete setup for more accurate measurements relatively complex and expensive.

Benefits of thermopile based solutions compared to microbolometers

Thermopile-based solutions also offer excellent pixel resolution, and operate across a wide range of temperatures. However, compared to microbolometer-based solutions, they are also relatively affordable and do not require frequent recalibration.

In short: thermopile-based sensor solutions offer excellent resolution, operate in a wide range of temperatures and do not require frequent recalibration in the field. Infrared temperature sensors have a great reputation for accuracy – provided they’re used in the right way.

Rapid readings for different scenarios with 2Ms proven IR solutions

Contactless thermometers and sensors rely on infrared technology to safely take temperatures non-invasively, hygienically and rapidly without compromising on accuracy. They can be built into hand-held equipment, or integrated into devices such as kiosks. Used correctly, infrared or no-contact thermometers are approximately as accurate as ‘traditional’ thermometers – but offer many additional benefits. 

Besides providing rapid, accurate temperature measurements, using infrared devices eliminates person-to-person contact, and there is no need to touch the device. As a result, potential transmission of viruses is minimised. There are numerous applications for contactless solutions. For example, they can be used when larger groups of people need their temperature taken, for example at the entrance to a building or a counter.

2M engineering has developed a variety of solutions that rapidly provide thoroughly accurate readings. These are more hygienic than ‘traditional’ thermometers that require physical contact, and just as easy to use. Specially-developed algorithms that calculate the difference between measurements play a vital role in these solutions, which are based on 2Ms competences in all areas of sensor technology application – from consulting and R&D to prototyping and production. In addition, every sensor that 2M makes is calibrated device by device, so that the deviation from the ‘gold standard’ is minimal.

This approach has resulted in a range of successful certified and validated solutions. Our challenge is always to find the best compromise between technology, manufacturability and user benefit. Would you like to know more about any of the temperature measurement technologies, or discuss how these might be used in your own unique situation? Our experts are happy to help. Get in touch today!

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CIR100 infrared temperature sensor