Types of thermometers

Liquid thermometers
The principle of operation of such a thermometer is based on the expansion and contraction of the liquid that fills the bulb changes its volume when oscillating at its own temperature.
Mechanical thermometers
The principle of operation of such thermometers is also based on expansion. Such thermometers differ in the special accuracy of measurements.

Gas thermometers
In contrast to liquid thermometers in gas, some kind of inert gas is used.
Digital thermometers
These mercury free thermometers are easy to use and the reading is displayed in a more convient form.