The core element of the digital thermometer is the temperature sensor, which uses the temperature sensor to output electrical signals, directly output digital signals or convert current signals (analog signals) into digital signals that can be recognized by the internal integrated circuit, and then display the digital signals on the display. The temperature of the table. The resolution of currently used temperature sensors can usually reach ±0.01°C.

The familiar traditional mercury thermometer is made according to the principle of thermal expansion and contraction. At the same time, in order to keep the reading stable after the thermometer leaves the body, there is a narrow joint between the mercury glass bulb and the glass tube of the thermometer, which greatly increases the surface tension of mercury. So as not to retract the glass bulb and disconnect the mercury column when the temperature drops. This is why the thermometer must be shaken every time a problem is measured. The accuracy of mercury thermometers can reach 0.1°C, which is slightly lower than that of digital thermometers, but it can fully meet the needs of clinical use.