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Accuracy of IR Thermometer Easily Affected by External Environment
Added:2020-08-01     Views:    

A..The accuracy of the infrared thermometer is easily affected by the external environment

Popularization of infrared thermometers due to "epidemic"

Fever is an important first symptom of infectious diseases such as SARS, avian influenza, and H1N1 influenza, and body temperature testing is the first step in the diagnosis of such cases. Therefore, temperature measurement is very important in disease prevention and clinical practice.

After the SARS epidemic broke out in 2003, people modified infrared thermometers originally used in industry to measure human body temperature and quickly spread in the field of medical care.

In 2009, the influenza A H1N1 epidemic raged around the world. At this time, the inspection and quarantine departments of ports nationwide basically adopted new infrared temperature measuring equipment. In recent years, continuously optimized infrared temperature measurement technology has been used for the prevention and control of Ebola hemorrhagic fever, Zika virus disease, and yellow fever epidemics.

With the continuous increase in the variety of non-contact infrared human body thermometers, the scope of application is also expanding, and the accuracy of medical infrared thermometers has also been improved, but in life, we will find the measurement results of infrared thermometers and The actual body temperature sometimes varies greatly.

B..Accuracy is easily affected by the external environment

Any object with a temperature greater than absolute zero (-273℃) continuously emits infrared radiation to its surroundings. Its energy is directly related to the surface temperature and wavelength distribution of the object. The surface can be measured according to the infrared energy of the object itself. Temperature, this is also the working principle of the medical infrared body temperature measuring instrument.

Infrared thermometers are generally composed of optical systems, photodetectors, signal amplifiers, signal processing, and display output. The optical system condenses the infrared radiation energy of the target in its field of view. The infrared energy is focused on the photodetector and converted into a corresponding electrical signal. The signal passes through the amplifier and signal processing circuit and is corrected according to the algorithm and target emissivity in the instrument Converted to the temperature value of the measured target.

Among them, the infrared detector is a device that quantifies infrared radiation signals and is the core of the entire infrared temperature measurement technology. It is mainly used to collect and quantify infrared radiation signals. Its core component is an infrared focal plane array. After this array collects infrared radiation signals of varying strength, they convert them into electrical signals, and then undergo a series of processing such as voltage amplification and conversion to finally quantify different values.

But the physical radiance will be affected by many factors, such as dust particles, water vapor, and infrared radiation has strong absorption. With the increase of the temperature measurement distance, the ability of the temperature measurement device to perceive radiation is also directly affected. If the temperature of the measured object is determined, under the influence of the measurement distance, the emissivity of the target, and the ambient temperature, the thermometer The temperature of the object felt will also vary, which will inevitably reduce the accuracy of the measurement.

C..Measuring the forehead is not as accurate as measuring the wrist

First , the measurement accuracy of the thermometer is related to the accuracy of the instrument itself and the quality of the instrument itself;
Second, the difference in measurement standards between the calibration temperature of the measuring instrument in the laboratory and the actual measured temperature may also easily cause measurement errors;
Third, the current thermometers are measuring the forehead, palms, face and other parts of a person. The measurement result belongs to the body surface temperature of a person, and the body surface temperature may fluctuate due to the influence of the person's activity state, so it is not necessarily Can truly represent human body temperature.

For example, when a person is riding a bicycle against the wind, the result is that the forehead thermometer shows 34°C or the value cannot be displayed. There is also a reminder in the manual of the forehead thermometer that the user and the infrared forehead thermometer should be kept at a stable room temperature for at least 30 minutes before use. But during the epidemic prevention and control period, we cannot wait for 30 minutes to take body temperature again.

After repeated tests, the staff of the Medical Engineering Department of Ningbo No. 1 Hospital developed a trick to measure forehead thermometers. Ask the person under test to expose the part of the skin of the wrist that is covered by clothes and not exposed to the air, and measure it at a distance of 6-8 cm from the wrist, so that the measured temperature is closer to the real temperature of the human body.

来源:科技日报 Source: Science and Technology Daily

http://www.ce.cn/cysc/yy/hydt/202002/20/t20200220_34314230.shtml


 
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