"China Metrology" magazine invited the main drafter of JJG1164-2019, Bai Chengyu, an associate researcher of China Institute of Metrology, to interpret JJG1164-2019.

In 2003, JJF1107-2003 "Infrared Thermometer Calibration Specification for Measuring Human Body Temperature" was promulgated and implemented; in 2008, GB/T21417.1-2008 "Medical Infrared Thermometer Part 1: Ear Cavity" was promulgated and implemented; in 2016, JJF1577-2016 "Infrared Ear Thermometer" was promulgated and implemented. In 2019, JJG1164-2019 "Infrared Ear Thermometer Verification Regulations" was promulgated and implemented, which together constitute a technical document system for ear thermometer verification, calibration, type evaluation test of measuring instruments and product inspection.

The direct measurement of the ear thermometer is the ear canal temperature. When outputting the measurement results, the data processing unit mathematically corrects the deviation of the emissivity of the measurement target (ear canal and eardrum combination) from 1. However, for a long time, people have been accustomed to use armpit temperature or oral temperature to represent human body temperature. temperature. In this adjustment, the data processing unit of the ear thermometer will introduce corrections for temperature differences in different parts of the human body. At present, there is no standard mathematical model for this correction. Usually, the ear thermometer manufacturer obtains or cites relevant literature data through experimental methods. The correction models of different products are quite different. Based on this working method of ear thermometer products, the management of ear thermometer accuracy in GB/T21417.1-2008 adopts a combination of "laboratory verification" and "clinical verification". Test the "laboratory error" of the ear thermometer under different temperature and humidity environments and mechanical environments, and test the "clinical repeatability" and "clinical deviation" under clinical conditions. The test data of the ear thermometer under laboratory conditions reflect the basic characteristics of the ear thermometer as a measuring instrument. "Accuracy is ±0.2°C, operating environment is 16°C ~ 35°C, humidity ≤ 85%RH" indicated in the ear thermometer product manual, it should be understood that the ambient temperature is 16°C ~35°C and ambient humidity ≤ 85%RH Under the conditions of , the laboratory error of a single measurement of the ear thermometer satisfies ±0.2°C.

The ambient temperature during verification is controlled within the range of 18°C ​​to 28°C, which is the same as the ambient temperature controlled during ear thermometer calibration according to JJF1107-2003. When conducting new product type evaluation of ear thermometers according to JJF1577-2016 or conducting product inspections according to GB/T21417.1-2008, the laboratory that tests the ear thermometers should be conducted under the ambient temperature lower limit, ambient temperature upper limit and damp-heat environmental conditions respectively. error.

Laboratory error is defined as the difference between the infrared ear thermometer indication and the black body temperature in the test mode. The test mode, also called the calibration mode, is a specific working state or mode of the ear thermometer. In this mode, the output result of the ear thermometer does not include the temperature correction of the body part. The laboratory error must be carried out in the test mode, and the setting method of the test mode is clearly described in the product manual. When there is no relevant information in the product manual, the manufacturer should be consulted to obtain the accurate calibration mode setting method.

JJG1164-2019 stipulates that the ear thermometer verification device is composed of ear thermometer black body cavity, liquid constant temperature tank, standard thermometer and supporting electrical measuring instruments. The black body cavity is located in the working area of ​​the liquid constant temperature tank, and the temperature control of the black body cavity is realized by controlling the temperature of the working medium in the working area of ​​the liquid constant temperature tank. The temperature of the black body cavity is characterized using the temperature of the liquid working medium measured by the standard.

Components, the structure, size and clear manufacturing process requirements of the standard ear thermometer blackbody cavity (model NIM G2) are given in Appendix A of JJG1164-2019. The emissivity of the blackbody cavity (8-14) μm wavelength range should not be lower than 0.999, and the opening diameter should be (8-10) mm. American Standard ASTM E1965-98 (2016) "Standard Specification for Infrared Thermometers for Intermittent Determination of Patient Temperature" and European Standard EN 12470-5 Final (E) 2003 "Medical Thermometers - No. Part 5: Infra-red ear thermometer performance requirements (Clinical thermometer-part 5: Performance of infra-red ear thermometers with maximum device) also released the structure size and process requirements of the black body cavity of the ear thermometer, as shown in Figure 2. These two ear thermometer cavities are used in ear thermometer manufacturers and measurement technical institutions in my country. Limited by the unsatisfactory level of direct measurement of cavity emissivity, the brightness temperature comparison experiment was used to determine the difference between the NIM G2 cavity and the cavity recommended by ASTM and EN standards in order to verify the NIM G2 cavity. Reasonableness of technical requirements. The experimental data showed no difference in the brightness temperature reproduced with the ASTM cavity and the NIM G2 cavity. Compared with the ASTM cavity, the size of the NIM G2 cavity is small, the cone apex angle (120°) at the bottom of the cavity is easier to process compared to the ASTM cavity’s 36.4°, the material cost is low and the machining difficulty is less. The NIM G2 cavity The advantages. The EN cavity reproduces the brightness temperature 0.01°C lower than that of NIM G2. Although 0.01°C is numerically equivalent to the display resolution of the brightness temperature comparator, considering the repeatability of the comparison experiment, the probability of the low emissivity of the EN cavity is relatively high, and it is recommended to use the EN cavity design with caution. In the measurement standard assessment, the device brightness temperature comparison method can be used to verify the device's ability to reproduce the value. It is recommended to carry out a brightness temperature comparison ability verification in the middle of the measurement standard review and assessment cycle.

The verification device adopts the second-class and above standard platinum resistance thermometer as the standard thermometer. The main reasons are the excellent stability of the standard platinum resistance thermometer, the mature verification technology, and the second-class standard platinum resistance thermometer in most provincial metrology technical institutions. The relatively complete and mature quantity traceability system can realize the stable and reliable traceability of the main standard.

In summary, JJG1164-2019 provides a clear solution for the realization of the ear thermometer verification device. This technical treatment is used to improve the feasibility of evaluating the performance parameters of the device, and to make full use of the existing mature measuring instruments and the perfect links in the traceability system to ensure the reliability of traceability. The expanded uncertainty of the reproducible value of the ear thermometer verification device specified in JJG1164-2019 is about 0.04°C. Compared with JJF1107-2003, JJG1164-2019 has stricter and clearer requirements on the metrological characteristics of metrology standards, and can meet the relevant requirements of JJF1107-2003, JJF1577-2016 and GB/T21417.1-2008 for standard devices.

3. Qualified determination of laboratory error

At the verification temperature points of 35 °C, 37 °C and 41.5 °C, the laboratory error of the three measurements at each verification temperature point does not exceed ±0.2 °C, and the laboratory error item is qualified, that is, the laboratory errors of the 9 measurements are qualified, the verification item qualified.