Why can't the temperature gun be measured? Maybe it was wrong in the first place...

"Your temperature is 36.2 degrees C" and "your body temperature is 35.3 degrees C" ... This is the normal way for journalists to measure their forehead temperature when they enter the workplace and return to their homes.We know that the body temperature of healthy adults is relatively constant, about 37 degrees C, due to the test site, time, season and individual differences and other factors slightly different, when the body temperature exceeds the normal value is called fever. During the prevention and control of the new crown pneumonia outbreak, 37.3 degrees Celsius of body temperature should be reported truthfully, and self-driving or contact 120 ambulances to the fever clinic.Are these infrared temperature tests reliable when we go out with this "gentle shot"? Is there an error? If the error is generally large, will it not be conducive to the prevention and control of the outbreak of neo-crown pneumonia? Where is the "one shot" aimed, and the data may be more accurate?Infrared thermometer because of the spread of "epidemic fever is SARS, avian influenza, influenza A H1N1 and other infectious diseases important first symptoms, and temperature testing is the first step in diagnosing such cases. Therefore, in disease prevention and clinical, temperature measurement is very important.At present, there are two common thermometers, one is a mercury thermometer as the representative of the contact measurement method, its measurement is more accurate, but there is a potential mercury hazard, there are many countries in the world have banned the use of mercury thermometers, and the other is the infrared thermometer as the representative of non-contact measurement, can greatly reduce the probability of cross-infection, and more convenient and fast. When some infectious diseases with fever symptoms occur, infrared thermometers are often widely used in hospitals, airports, stations, entry and exit quarantine sites and other public places where people gather.At first, because the technology is not mature enough, infrared temperature measurement technology is only used in the general industrial field, the temperature accuracy requirements are not high. At the same time, this non-contact temperature measurement method will be affected by a variety of external conditions, the accuracy of a certain impact. But after the SARS outbreak in 2003, infrared thermometers, originally used in industry, were slightly improved to measure human body temperature and quickly spread in health care.In 2009, the influenza A (H1N1) epidemic raged around the world. At this time, the national port inspection and quarantine departments have basically adopted a new type of infrared temperature measurement equipment. In recent years, the continuous optimization of infrared temperature measurement technology for Ebola haemorrhagic fever, Zika virus disease, yellow fever outbreak and other prevention and control work.With the increasing variety of non-contact infrared human thermometers, the scope of application is also expanding, the accuracy of infrared thermometers for medical use has also been improved, but in life, we will find that infrared thermometer measurement results and actual body temperature will sometimes appear large differences.Accuracy is susceptible to external environmental influencesInfrared was first known in 1800, when British astronomer William Herschel discovered that everything in nature that is above absolute zero (-273 degrees Celsius) radiates infrared light every moment. Then, in 1821, german scientist Sebeck discovered the Sebeck effect, and in 1859, German physicist Kirchhoff based his theory of thermal equilibrium on the law of Kirchhoff radiation. These studies provide the most powerful theoretical basis for the effective development of infrared technology, and infrared technology has been developed and widely used. Based on these principles, the infrared energy of an object's radiation can be collected, quantified, and then the temperature of the object calculated from the quantitative results.That is to say, any object whose temperature is greater than absolute zero is constantly emitting infrared radiation to the surrounding area, and its energy size has a direct relationship with the surface temperature and wavelength distribution of the object, according to the infrared energy of the object itself, its surface temperature can be measured, which is also the working principle of the medical infrared thermometer.Infrared thermostats are generally composed of optical systems, photodeters, signal amplifiers and signal processing, display output and so on. The optical system aggregates the target infrared radiation energy in its field of view, which is focused on the photoderactor and transformed into the corresponding electrical signal, which passes through the amplifier and signal processing circuit and is corrected according to the algorithm and target rate within the instrument and converted to the temperature value of the target under test.Among them, the infrared detector is a device for quantifying infrared radiation signal, is the core of the whole infrared temperature measurement technology, mainly used to collect infrared radiation signal and quantify, the core component of which is the infrared focal plane array. The array collects infrared radiation signals of varying strength and strength, converts them into electrical signals, and then processes them through voltage amplification, conversion, etc., and finally quantifies different values.However, physical radiation is affected by a variety of factors, such as dust particles, water vapor, and infrared radiation has a strong absorption. Under the increase of temperature measurement distance, the temperature measurement device's ability to perceive radiation is also directly affected, if the temperature of the object under test is determined, under the influence of measuring distance, target object emission rate, ambient temperature, the temperature of the object felt by the thermometer will also be different, which will inevitably reduce the accuracy of the measurement.Therefore, in order to get accurate measurement data, the core is to improve the quality standards of the product. One method is to calibrate the infrared thermostat, and the second method is to set the emission rate of the infrared thermostat correctly in practice. We still leave these tasks to the manufacturers because that's not what the average person or a community temperature measurement worker can do.The forehead may not be as accurate as the wristExperts from the China Institute of Metrology Technology said in a media interview that the accuracy of the thermometer is first related to the accuracy of the instrument itself and the quality of the instrument itself , it is also easy to cause measurement errors; third, now the thermometers are measured on the forehead, palm, face and other parts of the human body, the measurement results belong to the human body surface temperature, and the body surface temperature may be affected by the state of human activity fluctuations, so it does not necessarily represent the human body temperature. 　　For example, when a person rides a bicycle against the wind, the resulting thermostat measurement shows 34 degrees C or can not display a value. There is also a reminder on the instruction manual of the erythrine gun that users and infrared thermometers should be kept at a stable room temperature for at least 30 minutes before use. But during the outbreak prevention and control period, we were unable to wait 30 minutes before we could take our temperature. 　　After repeated testing, the staff of the Medical Engineering Department of Ningbo No. 1 Hospital developed a tip for measuring the thermostat. Ask the person to expose the part of the wrist covered by clothing, not exposed to the air, at a distance of 6-8 cm from the wrist measurement, so that the measured temperature is closer to the real temperature of the human body. (Science and Technology Daily)