A thermometer is an instrument used for measuring temperature. This device measures temperature in degrees Celsius and can register temperatures of up to 200°C.

The thermometer consists of a glass tube with a small capsule at its tip containing mercury. A very thin opening at the end of the capsule leads into a narrow capillary tube. Mercury is highly sensitive to temperature changes: as the temperature rises, the mercury expands and moves upward through the capillary.

The scale marked on the thermometer is calibrated according to the distance the mercury travels for each change in temperature.

This type of thermometer is used primarily in industry.