  The non-contact infrared thermometer (NCIT) is an important basic tool for
fever screening and self-health monitoring. However, it is susceptible to the
thermal shock when working in a low temperature environment, which will cause a
time-consuming and inaccurate human body temperature measurements. To overcome
the effects of thermal shock, a hybrid temperature compensation method
combining hardware and algorithm is proposed. Firstly, the principle of
infrared temperature measurement is described and the influence of thermal
shock on infrared thermometer is analyzed. Then, the hybrid temperature
compensation scheme is constructed by mounting a heating ring on the infrared
sensor shell, and using the proportional integral derivative (PID) algorithm
and the pulse width modulation (PWM) technology to control it heating. In this
way, the internal ambient temperature of infrared sensor can be raised rapidly
closing to the external ambient temperature, and the stable outputs of the
infrared sensor are also accelerated. Finally, some experiments are carried out
in a laboratory. The results show that the proposed method can quickly and
accurately measure the temperature of standard black body when the ambient
temperatures are 5 , 15 and 25 Celsius respectively, the measurement error is
only 0.2 Celsius , and the measurement time is less than 2 seconds. This study
would be beneficial to improve performance of NCIT, especially the infrared ear
thermometer.
