The ear thermometer is a non-contact telemetry (although it may be less than one centimeter) temperature measurement instrument. It uses the infrared spectrum emitted by the eardrum (equivalent to the hypothalamus) to determine the body temperature. According to the black body radiation theory, it is different The infrared spectrum produced by temperature objects is also different. The thermopile infrared detector can be accurate to 0.1 ℃, and then converted by the microcomputer to display the reading.

There is a place called the hypothalamus in the deep part of the brain. There is a "set-point" structure that controls the human body's temperature. The hypothalamus is also the center point of the body's temperature. When the body has a fever, it is the result of a "fixed point" after receiving some inflammatory chemicals that patrol in the bloodstream. The hypothalamus is the place where the body temperature rises first, and the blood supply to the eardrum and the hypothalamus It happens that there is traffic with each other, so it is most appropriate to use the eardrum temperature to reflect the temperature of the human body. At the same time, the eardrum can also be the earliest place to detect whether the human body has a fever.