Infrared thermometers use infrared rays with a wavelength between 0.76 and 100 μm to scan and image objects to perform on-line fault diagnosis and safety protection of objects and save energy, etc. Therefore, infrared thermometers have always been countries Important research projects, including in daily life and even in the medical field, have played an important role. We have detected many unseen problems for us, but what is his working principle?
1. Theoretical principle of infrared temperature measurement
In the natural world, when the temperature of an object is higher than absolute zero, due to its internal thermal motion, it will continuously radiate electromagnetic waves to the surroundings, which includes infrared rays with a wavelength range of 0.75μm ~ 100μm. His biggest feature is that at a given temperature and wavelength, the radiant energy emitted by an object has a maximum value. This substance is called a black body, and its reflection coefficient is set to 1, and the reflection coefficient of other substances is less than 1. It is a gray body, because the spectral radiation power P (λT) of the black body and the absolute temperature T satisfy Planck's order. It shows that at an absolute temperature T, the radiation power of a black body per unit area at the wavelength λ is P (λT). According to this relationship, the corresponding relationship curve can be obtained, namely:
(1) As the temperature increases, the stronger the radiant energy of the object. This is the starting point of infrared radiation theory and the design basis of single-band infrared thermometer.
(2) As the temperature rises, the radiation peak moves to the short-wave direction (to the left), and satisfies the Wien displacement theorem, the wavelength at the peak is inversely proportional to the absolute temperature T, and the dotted line is the peak connection at. This formula tells us why high-temperature thermometers work mostly at short waves, and low-temperature thermometers work mostly at long waves.
(3) The rate of change of radiant energy with temperature, the short wave is larger than the long wave, that is, the pyrometer working at the short wave has a relatively high signal-to-noise ratio (high sensitivity) and strong anti-interference. This is especially important at wavelengths, especially in the case of small targets at low temperatures.
2. Working principle of infrared thermometer
Infrared thermometer is composed of optical system, photodetector, signal amplifier, signal processing, display output and other parts. The radiation of the measured object and the feedback source is modulated by the modulator and input to the infrared detector. The difference between the two signals is amplified by the amplifier and controls the temperature of the feedback source so that the spectral radiance of the feedback source is the same as the spectral radiance of the object. The display indicates the brightness temperature of the measured object.
3. Application of infrared thermometer
Infrared thermometers were generally used in meteorological departments and safety inspection departments before, to detect the real-time average temperature and city heat distribution of cities. With the rapid development of our science and technology in infrared thermometers, the functions continue to increase, the variety has become more and more, and the fields of application have gradually become wider. Now the market share of infrared thermometers is gradually increasing. Step by step in the home, monitoring the outdoor temperature in real time in the home, allowing users to change the clothes they wear in time to avoid the appearance of some diseases, and then being able to map the distribution of the home temperature in real time, which is conducive to us Change the problem of uneven temperature in the home in time. It can also be used in the field of human body or object temperature measurement, such as human body temperature measurement in medicine, industrial machine temperature measurement, etc., so its related price will also be different.
4. Precautions for using infrared thermometer
4.1 The infrared thermometer only measures the surface temperature of the object.
4.2 If we measure the temperature across the glass, it may cause the inaccurate reading of the infrared thermometer.
4.3 When using infrared thermometers, try to avoid using them in places where there is a lot of steam or dust. So as not to damage the instrument.
5. General performance parameters of infrared thermometer
The temperature range for professional use is between -50 degrees and 1600 degrees. The distance used is within 50 meters. The accuracy is 0.001, and the corresponding time is less than 1 second.
For human body temperature measurement, the normal body temperature can be measured from -10 degrees to 40 degrees through software algorithm and black body source calibration. When the temperature is lower than minus zero, the system needs to set the compensation temperature. For example, SA200P uses a medical-grade infrared temperature probe to accurately and quickly measure temperature for the initial screening of fever patients to prevent cross infection of epidemics. For more information, please pay attention to: https://www.securinadetection.com/product/Securina-SA200P-Portable-Infrared-Thermometer-for-Body-Temperature-MeasuringUnattended.html
