Research On Thermal Shock Effect And Preheating Compensation Method Of Non-contact Infrared Thermometer

Body temperature measurement is a basic method to check the health of the human body,and accurate measurement of human body temperature is an important basis for disease diagnosis.In recent years,with the continuous outbreak of large-scale febrile infectious diseases on a global scale,rapid and accurate body temperature measurement technology has received widespread attention.Traditional contact mercury thermometers have high measurement accuracy,but the measurement speed is slow,and there is a risk of cross-infection.Infrared thermometers have the advantages of fast response speed,simple operation,non-contact measurement,etc.,and the measurement accuracy is basically comparable to mercury thermometers in normal temperature working environment,so it is widely used in the occasion of rapid and efficient screening of fever population,such as epidemic prevention and control.However,when the internal temperature of the infrared thermometer is not balanced with the working environment temperature,it will form heat exchange,and even produce thermal shock,which will affect the measurement accuracy.In very special cases,the infrared thermometer even can not work normally.Especially when the infrared ear thermometer is inserted into the high-temperature ear canal from a low-temperature environment,thermal shock is inevitable.Therefore,it has important research value and practical significance to reduce or overcome the influence of thermal shock on infrared thermometer.Aiming at the thermal shock problem of infrared thermometers,this thesis proposes a hybrid warm-up compensation method that combines hardware and algorithms.The thesis analyzes the principle of infrared temperature measurement,the structure of infrared sensor and the causes of thermal shock.Designed an infrared sensor preheating device using integral separation PID(proportional,integral,differential)algorithm and PWM(pulse modulation width)technology.Through the device,the internal ambient temperature of the infrared sensor can be preheated to a set temperature before measuring the body temperature,and the temperature of the working environment can be kept relatively balanced,so as to achieve the purpose of eliminating the influence of thermal shock.Based on the theory of heat conduction,a preheating simulation model for the internal ambient temperature of the infrared sensor was established,and a simulation experiment was carried out using Simulink in MATLAB software to verify the feasibility of the preheating method.Then select the STM32 chip to design the infrared temperature measurement hardware system.Based on the Keil MDK u Vision5 software,the program of the preheating method is completed,and the experimental test is carried out on the hardware system to realize the PID control of the PWM waveform output and the precise preheating of the infrared sensor.The temperature function,and the body temperature measurement function under this condition.In order to verify the effectiveness of the method,an experimental environment was built based on a walk-in constant temperature laboratory and standard blackbody,and a series of test experiments were carried out.The results show that the method in this thesis can stably preheat the internal temperature of the infrared sensor to the set temperature within 3s under the initial ambient temperature of 5 ℃ to 15 ℃,and the measurement error of the standard blackbody temperature is only ±0.2℃,which effectively eliminates The thermal shock has reached the standard of JJG 1164-2019 infrared ear thermometer.