Kinds of thermometer

You are likely to meet two kinds of thermometer:

• Clinical thermometers measure human body temperature.
• Laboratory thermometers are used for many other purposes.

The clinical thermometer you may have at home shows the temperature as numbers on a small screen, so it is called a digital clinical thermometer. It runs on batteries. It measures the temperature when it touches the body, using heat sensors inside.

Earlier, mercury thermometers were used for body temperature. But mercury is extremely toxic (poisonous), and if the thermometer breaks it is hard to get rid of the mercury safely. Digital thermometers have no such risk, and their numbers are easier to read. So mercury thermometers are being replaced by digital ones.

During the COVID-19 pandemic, special thermometers were used that measure temperature from a distance. They are called non-contact or infrared thermometers. You point one at a person's forehead without touching them, so it reduces the risk of spreading disease.