It all start with the sensor. Unlike the liquid-filled thermometer and the bi-metal thermometer, a digital thermometer needs a sensor.
These sensors all produce either a voltage, current, or resistance change when there is a change of temperature. These are “analog” signals as opposed to digital signals.They can be used to take temperature readings in the mouth, rectum, or armpit.
Electronic thermometers work in an entirely different way to mechanical ones that use lines of mercury or spinning pointers. They're based on the idea that the resistance of a piece of metal (the ease with which electricity flows through it) changes as the temperature changes. As metals get hotter, atoms vibrate more inside them, it's harder for electricity to flow, and the resistance increases. Similarly, as metals cool down, the electrons move more freely and the resistance goes down.
The below is our high accuracy popular digital thermometer for your reference :