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https://www.senbasensor.com/temperature-measurement-accuracy-of-infrared-thermopile-sensor-at-different-distances.html

Infrared thermopile sensor combined with Fresnel lens can greatly enhance its detection range. In general, the maximum distance of detecting the surface temperature of human body can reach 6-10m under ideal conditions.

The distance coefficient ratio can be expressed as D:S, that is to say, if the object (eg: circle) is D away from the detector, the temperature measurement is accurate as long as the diameter of it is greater than S. If the diameter of the object is less than S or the shape of the object is irregular, part of the infrared signal received by the infrared thermopile sensor will show the ambient temperature behind the object, which will cause the obtained temperature to be lower or higher (usually lower). If the detection distance is less than D, it will be reduced according to the proportion of D:S. Therefore, the closer the detection distance is, the higher the probability of measurement accuracy is.

In general, as long as the object is large enough or the object is fully covered by detection spots, the detection accuracy will not be affected by the distance.

For the new thermoprobe, the detection accuracy is generally ± 1.5℃; for the internal sensor, if the influence of Fresnel lens, mounting cavity and subsequent circuit design is eliminated, the maximum detection accuracy is ± 0.1℃.

For ear thermometer, the detection distance between the sensor and the inner ear is very close, so it can be directly used for temperature measurement without adding Fresnel lens. At this time, the measurement accuracy is greatly improved. However, due to the different design structure of the ear thermometer probe shell, the temperature measurement accuracy will be different. Generally speaking, the temperature measurement accuracy of the ear temperature gun is within ± 0.2℃~ ± 0.3℃, while the detection accuracy of the sensor can still reach ± 0.1℃.

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