Measuring body temperature is the basic work in a clinic, and the accuracy of the temperature measurement results has an important impact on the doctor's understanding of the patient's condition, infrared temperature measurement not only reduces the chance of cross-infection but also avoids the contamination of mercury, so this method of temperature measurement is gradually being widely used. This paper will analyze the development status of various types of medical thermometers in detail, focusing on common infrared thermometers such as ear cavity thermometers, epidermal thermometers, medical infrared thermography, infrared temperature monitors, etc., and summarizing the advantages and shortcomings of various types of medical infrared thermometers.
The most common thing in clinical medical care is body temperature measurement, because body temperature is the most important symptom showing human vital signs, and its measurement results can help doctors understand the patient's condition and serve as a reference for subsequent treatment plans. There are currently two common methods of measuring body temperature:
1. Contact measurement represented by the mercury thermometer;
2. non-contact as represented by infrared thermometers
The infrared thermometer does not need to have direct skin contact with the person being measured, and it is more convenient and quicker compared with the mercury thermometer. Therefore, when some of the fever symptoms of infectious disease outbreaks, it is widely used in many public places such as stations, airports, and so on.
Development of infrared thermometry
Infrared light was first discovered in the 1800s when astronomers in England discovered that when the temperature of a thermometer changed, it would produce invisible radiation with a frequency below that of red light. This was followed by the discovery of the Seebeck effect by German scientists, and later by Kirchhoff's law of radiation by German physicists based on the theory of thermal equilibrium. These findings for the effective development of subsequent infrared technology provide the most favorable theoretical basis, infrared technology has been widely used and flourished.
At the beginning of infrared temperature measurement, the technology is not very mature, although its measurement speed will be relatively fast compared to other thermometers, its degree of accuracy for the temperature is more general. Therefore, it is only used in the general industrial field that does not require high-temperature accuracy. However, although mercury thermometers are more accurate, they also have potential mercury hazards, and many countries around the world have already banned the use of mercury thermometers. Therefore, after the SARS virus outbreak in 2003, infrared thermometers, a non-contact method of measuring body temperature, were rapidly developed in healthcare. The initial application of infrared thermometers in healthcare was to deal with the risk of virus transmission in an emergency, and therefore only a slight modification of the infrared thermometers commonly used in industry was put into use. In recent years, with the continuous efforts of various scholars, the degree of accuracy of infrared thermometers for medical use has been improved, and other functions have been gradually improved, and good results have been achieved in the subsequent outbreaks of the flu battle. However, because of this non-contact temperature measurement method is still subject to various external conditions, resulting in a certain degree of temperature accuracy being affected. Therefore, the state also on the medical infrared thermometer error value for a clear limit, limit the error value of ± 0.2 ℃.
Current status of infrared thermometry
The infrared temperature measurement technology applied to the medical field is not long, so if you want to distinguish from the various types of infrared thermometers, you can simply be divided into the following four kinds, they all belong to the infrared thermometer, but each has its advantages.
（1）Ear Cavity Thermometer
Generally speaking, the best place to assess a person's body temperature is considered by the medical profession to be the temperature of the eardrum, as its blood vessels are directly connected to the hypothalamus, which regulates the body's temperature. Initially, the eardrum temperature was measured by using a thermistor in contact with the eardrum, but due to the strong requirements for the operator's skills, the eardrum can be harmed if not careful. It wasn't until the introduction of the infrared thermometer designed for the ear cavity in 1986 that the measurement of body temperature through the eardrum became popular. However, the use of this device also requires a certain level of skill on the part of the operator, and since the probe is inserted into the ear cavity, it is necessary to have a disposable probe for testing to prevent cross-contamination.
（2）Epi-Thermometers
Also known as a forehead thermometer, this epidermal thermometer works by measuring the temperature of the human epidermis. The working principle of the forehead thermometer is similar to that of the ear thermometer, but it is not as accurate as the ear thermometer that measures the eardrum, because the temperature of the human epidermis will be affected by various external factors during the measurement of the forehead thermometer, resulting in a difference between the forehead temperature and the real body temperature. Therefore, the results of this measurement can not be used as a basis for clinical diagnosis.
（3）Medical Thermal Imaging Cameras
The principle of this measurement method is the same as the above, but the collection and processing of signals is relatively more complex than theirs, because this method is the whole person's body temperature directly with two-dimensional images of the way to intuitively present, so the use of this instrument is more costly, so its application range is also more narrow.
（4）Infrared Temperature Monitor
This instrument is widely used with the outbreak of various infectious diseases with fever characteristics in recent years, as it can not only quickly measure the temperature of each human body in a certain area, but also does not need to directly contact the target population, maximizing the avoidance of cross-infection. Therefore, it is widely used in major public places.
Factors influencing the application of used infrared thermometers
Any object with a temperature greater than 0, is constantly emitting infrared radiation to the surrounding area, the size of its energy the surface temperature of the object, and the wavelength distribution have a direct relationship, according to the object's infrared energy, you can determine the surface temperature, which is also the working principle of the medical infrared thermometer. On the one hand, the object temperature and object radiance, object emissivity, and Boltzmann's constant are related, the physical radiance will be affected by a variety of factors, such as dust particles, water vapor, and infrared radiation has strong absorption. Under the increase of the temperature measurement distance, the ability of the thermometer device the perceive radiation is also directly affected, if the temperature of the object to be measured is determined, under the influence of the measurement distance, the target object emissivity, the ambient temperature, the temperature of the object perceived by the thermometer will also be different, which will inevitably reduce the accuracy of the measurement.
Since infrared temperature measurement not only reduces the chance of cross-infection, but also avoids mercury contamination, this method of temperature measurement is gradually being widely used, but the disadvantage of temperature error in infrared temperature measurement should not be ignored as well. Therefore, under the premise of improving work efficiency and protecting the natural environment, the use of infrared temperature measurement is an inevitable trend, but in clinical medicine should be combined with mercury and infrared temperature measurement, only in this way can ensure the accuracy of the measurement results.
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