The principle and characteristics of infrared human body thermometer
The overall working concept of an infrared human body thermometer is that the heat radiated by the human body generates an infrared energy. The automatic thermometer can automatically measure the infrared energy radiated by the human body and convert it into temperature, which is displayed on the screen. The circuit of the infrared human thermometer is still quite complex. To simplify the problem, we use a principle diagram to illustrate its working process. Its overall structure consists of an optical structure part, a photodetector part, an amplifier part, and a signal processing part, such as the filter and integrator shown in the figure below, as well as a display output part. The main task of optical mechanisms is to capture the energy of infrared radiation on the surface of the human body, and then focus the energy of infrared radiation in photodetectors and convert it into electrical signals. In fact, it is also the thermal infrared sensor in our industrial control field. Because the electrical signal it converts is very weak, it needs to be amplified by an amplifier and used for the signal processing circuit of the next stage. The signal processing circuit mainly filters out some interference signals and adjusts the waveform of the signal, usually implemented by integrators and other circuits. Finally, the processed signal is converted into a digital circuit through an A/D converter and the human body temperature is displayed on an LCD monitor. The above is the general working process of this instrument.
Characteristics of infrared human thermometer
I think the main features of this infrared handheld instrument for human body temperature measurement are as follows: firstly, it can measure the temperature of the human body in a non-contact manner, which is safe and efficient; The second is high sensitivity and accuracy in measurement, generally accurate to 0.1 degrees Celsius. The third is fast response. The time from measuring to collecting the surface temperature of the human body is generally in the millisecond range, and some can reach the subtle level, which is thousands of times faster than the temperature measurement speed of our traditional thermometers.
The basic theory of infrared temperature measurement is that when a substance is above absolute zero (-273.15 degrees Celsius), its molecules undergo thermal motion and radiate infrared radiation outward from its surface, which increases with temperature.
There is a pyroelectric infrared sensor installed in front of the infrared thermometer. When the infrared sensor senses the heat radiated outward by the human body (infrared radiation with intensity corresponding to body temperature), an electrical signal is generated at the output of the sensor. This electrical signal representing temperature is then amplified and processed, and finally transmitted to the display screen, where we can see the temperature value.
