In the recent outbreak of covid-19, fever usually appears as the first symptom after infection, so measuring body temperature has become the main means of screening suspected cases, especially in hospitals, subway stations, railway stations and other crowded places.

At present, the most common tools for measuring body temperature on the market are divided into three categories: the first category is thermometer, including common mercury thermometer and electronic thermometer, which are mostly used at home; The second type is the temperature measuring gun, which relies on the sensor to receive the infrared ray of the human body to judge the body temperature, and converts it into the body temperature through the formula. Generally, a single person can complete the temperature measurement in 3-5 seconds; The third type is the infrared thermal imager temperature measurement, which has attracted much attention recently. By transforming the invisible infrared energy emitted by the human body into a visible thermal image, simply speaking, it makes the temperature change from a numerical value to an image full of temperature data. Efficiency is one of its biggest advantages.

How does infrared thermograph temperature measurement achieve accurate screening of human body temperature? Recently, Li Gongzuo, an application engineer, from the domestic listed company focic feijike, which has focused on the research and development of thermal images for 10 years, answered the technical questions.

First of all, Li Gong takes the temperature measurement demand of the crowded railway station as an example. The daily passenger flow is 100000 person times. If you use a temperature gun to screen everyone’s temperature, it takes 83 hours or about 3.5 days to measure 100000 person times according to the average 3 seconds of a person, which is obviously unreasonable.

Of course, multiple entrances can be opened to disperse passenger flow, but passengers still need to stop for 3-5 seconds to pass. However, if the infrared thermal image thermometer is set, the flow of people can be ensured to pass at normal speed without close contact between people.

Then, how to realize the accurate screening of human body temperature by infrared thermal imager temperature measurement, Li Gong of foctic flight Foundation Department analyzed from the following points:

1、 Why is infrared thermal imager the most efficient way to measure temperature at present

The reason why the infrared thermal imager can screen body temperature is that it can convert the temperature into a visual image. The pixels in each thermal image are temperature points, and the number of temperature points is related to the infrared pixels of the device itself. For example, the infrared pixels of the FOC 692 are 384*288, that is, there are 110000 temperature points in a thermal image, which is equivalent to using 110000 temperature measuring guns to measure temperature at the same time, and the efficiency will be significantly improved.

2、 The temperature difference between normal temperature and abnormal temperature of human body is very small. How to recognize it through thermal image

The higher the thermal sensitivity of the infrared thermal imager, the stronger the ability to distinguish small temperature differences, and the more accurate the temperature measurement. If the thermal sensitivity of an infrared thermal imager is 0.03 degrees Celsius, the thermal imager can distinguish the temperature difference of 0.03 degrees Celsius, which can well meet the demand for high accuracy of body temperature screening. Technical parameters such as thermal sensitivity can be launched only after obtaining metrological certification from national metrology institutions. The focus thermal imager has such qualification certification.

3、 For such an accurate temperature measurement demand, whether there are fluctuations in temperature measurement data that affect the temperature measurement results

If we deeply study the infrared thermal imaging technology, we will know that there are two very important indicators to judge whether an infrared thermal imager is professional and reliable, namely “temperature measurement stability” and “temperature measurement consistency”. For example, a focus thermal imager shows in the test report of China Electric Power Research Institute that the fluctuation of the test results is very small (the fluctuation value is between 0 ℃ -0.03 ℃) when the test target of 49.8 ℃ is continuously measured for 2 hours, and when measuring the same blackbody target, the values of 9 areas in the same picture are basically the same, It can be said that the stability and consistency of temperature measurement meet the requirements of accurate measurement.

4、 How to catch abnormal body temperature when using infrared thermograph to screen body temperature

If there are people with abnormal temperature in the crowd, the automatic infrared temperature screening instrument of NUTRIC will automatically send out a beep to give an audible alarm, and the over temperature part in the picture will automatically display in red, and lwlir temperature screening software will automatically capture a thermographic photo of the over temperature person, which is convenient for later staff statistics and analysis.

As a non-contact temperature measurement tool, infrared thermal imager has been widely used in daily inspection of power industry, troubleshooting of factory equipment, quality control of processing industry, safety production of steel and petrochemical industry, material research of biological research and other fields. Its non-contact, image temperature imaging, efficient screening and other characteristics have been concerned by large-scale body temperature screening sites, such as airports, railway stations Subway stations and other traffic hubs, hospitals, large enterprises and institutions, schools and other crowded social places have been widely used.

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