How does a digital thermometer works?
Usually, the sensor is of a type called a thermistor, which is derived from “thermal resistor”. There are several types, some packaged as thermometers, others are sensors wired to network controllers and other application devices.
It is a resistor that has a very precise relationship in Ohms resistance at a specific calibration temperature.
The higher the Ohm rating, the more precise and accurate the sensor is.
When activated, a small electrical current is applied across the thermistor and the Ohms resistance is read. The corresponding temperature is then displayed digitally. The thermometers have the tables in resident non-volatile memory.