{"id":4333,"date":"2019-02-20T20:00:15","date_gmt":"2019-02-20T19:00:15","guid":{"rendered":"https:\/\/msalamon.pl\/?p=4333"},"modified":"2025-12-27T19:57:52","modified_gmt":"2025-12-27T18:57:52","slug":"how-does-chuck-norris-measure-temperature-he-looks-at-it-mlx90614-on-stm32","status":"publish","type":"post","link":"https:\/\/msalamon.pl\/en\/how-does-chuck-norris-measure-temperature-he-looks-at-it-mlx90614-on-stm32\/","title":{"rendered":"How does Chuck Norris measure temperature? He looks at it! MLX90614 on STM32."},"content":{"rendered":"\n

This time we\u2019ll be like the titular Chuck Norris because we\u2019ll be measuring the temperature of objects without touching them at all. The distance temperature sensor MLX90614<\/a> will help us with that. <\/p>\n\n\n\n\n\n\n\n

MLX90614 Pyrometer<\/h1>\n\n\n\n

This is a pyrometer<\/a>, i.e., a sensor that measures temperature based on the thermal radiation emitted by an object. Every object emits such radiation. It is perceptible to humans (you feel heat as you approach a hot object). Above all, this radiation is emitted most strongly in the infrared range. This means it is not visible to the human eye (I wrote a bit about the spectrum of visible light here<\/a>). Of course, there are exceptions \u2013 bodies heated above 600\u00baC can emit waves short enough to fall within the visible range, specifically red. That\u2019s why highly heated metal glows red.<\/p>\n\n\n\n

The pyrometer\u2019s task is to analyze this radiation and, based on it, determine the temperature of the object. In practice, this will be the surface temperature.<\/p>\n\n\n

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Field of View \u2013 FOV<\/h2>\n\n\n\n

Such sensors have one basic drawback (or maybe an advantage for some?). They have a certain fixed field of view<\/strong>. Hence, their measurement area depends on the distance from the object under test. This is exactly the same behavior as an ultrasonic distance sensor (Cheap ultrasonic rangefinder HC-SR04<\/a>) \u2013 the farther the sensor is from the object, the larger the object should be for the measurement to be reliable.<\/p>\n\n\n\n

There are several versions of the MLX90614<\/a> with different FOVs. The ranges for different types are shown in the table below from the documentation.<\/p>\n\n\n

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We have sensors with one and two active areas at our disposal. The module I have from China GY-906<\/a> has a MLX90614ESF-BAA<\/a> mounted, so the field of view of my unit is 72\u00ba. This is a very wide angle, so remember to measure the temperature from the shortest possible distance to the object.<\/span><\/p>\n\n\n\n

Some key data from the documentation (
MLX90614 Datasheet<\/a>
):<\/p>\n\n\n\n