Infrared thermometer does not emit infrared rays to measure temperature?
What is blackbody radiation?
What exists in the world is reasonable, and what exists does not have its own meaning and value. It's rare to find infrared light. What can it do? We can use infrared rays as remote controls, and remote sensing technology takes advantage of the long wavelength of infrared rays. Of course, there is also the temperature measurement we are talking about. So how does an infrared thermometer use infrared rays to measure temperature? First, let's understand blackbody radiation. The so-called black body refers to a black object? A black body is actually an idealized object that can absorb all external electromagnetic radiation without any reflection or transmission. No matter what object, as long as its temperature is higher than absolute zero, it radiates electromagnetic waves. Electromagnetic waves are oscillating particle waves emitted in space by electric fields and magnetic fields that are in phase and perpendicular to each other. They are electromagnetic fields that propagate in the form of waves. A black body looks black when it is below 700K, but that is only because the radiation energy emitted by a black body below 700K is very small and the radiation wavelength is outside the visible light range. If the temperature of the black body is higher than the above temperature, the black body will no longer be black, it will start to turn red, and as the temperature increases, orange, yellow, white and other colors will appear. Taking steel as an example, according to the rising temperature process, it turns red, orange, and yellow respectively. When the temperature exceeds 1300 degrees Celsius, it starts to turn white and blue. When a black body turns white, it also emits a large amount of ultraviolet light.
Among them, the radiant power per unit area is called p, T is the absolute temperature, and σ is a constant. The sun can be approximately regarded as a black body. People have measured the radiant power per unit area of the sun's surface to be 6×10^7 watts per square meter. According to the above formula, it can be concluded that the sun's surface temperature is 5700 Kelvin, or 5153.7 degrees Celsius. This is the first time humans have calculated the sun's surface temperature. .
The surface temperature of the sun can be measured far away in the sky, so wouldn't it be easy to measure the surface temperature of the human body right in front of us? So that's what we saw. The staff fired at us with the infrared thermometer in their hands. The infrared thermometer can collect the radiation power per unit area on the forehead and get your body temperature. The human body temperature is around 37°C, and the radiated electromagnetic waves are mainly concentrated in the infrared band, so this method of temperature measurement is called infrared temperature measurement. Seeing this, we understand that the infrared thermometer does not emit infrared rays to measure temperature by itself, but our human body radiates infrared rays, and the infrared thermometer collects these infrared rays.
What did it take from firing the gun to showing the numbers?
Now we know that the infrared thermometer collects the infrared radiation power per unit area on the forehead, and we also know that the temperature can be obtained through the formula, so how can we get the temperature value displayed on the display? Infrared thermometer consists of optical system, photoelectric detector, signal amplifier, signal processing, display output and other parts. The optical system converges the target infrared radiation energy within its field of view, and the infrared energy is focused on the photodetector and converted into a corresponding electrical signal. The electrical signal is amplified, filtered, converted to analog-to-digital, and sent to the microcontroller (a small but complete microcomputer integrated on a silicon chip) for signal processing. The liquid crystal display unit displays the temperature value of the measured target.
