Thermometer

A thermometer is a device that measures temperature. Read all about how different thermometers work and check out great thermometer resources!

How does a baby thermometer work?

A thermometer is a device that measures temperature. For example, you can measure the temperature of different objects with a thermometer to see how hot or cold a room is. Or cooked. Temperature is usually expressed in Celsius, but can also be expressed in Fahrenheit. Celsius and Fahrenheit are two different scales for measuring temperature. The main types of thermometers are modern digital thermometers, including infrared thermometers, and older mercury thermometers.

Mercury thermometer

A mercury thermometer looks like a sealed glass tube with a liquid inside and a number indicating the temperature on the side. The liquid is called mercury, and because it changes from solid to liquid very easily, it is ideal for temperature measurements and is the only metal that is liquid at room temperature. Mercury has a high boiling point, which makes it suitable for high-temperature measurements.

How does a mercury thermometer work?

When the tip of a mercury thermometer touches the material being measured, the material transfers heat energy to the mercury. The mercury then expands as it liquefies and begins to rise in the tube.

The point where the mercury stops on the scale is where the temperature can be read. It's comfortable! However, this thermometer is discontinued because mercury becomes toxic if the thermometer fails.

Digital Thermometer

Digital thermometers use electronic computer chips to measure temperature. The tip of a digital thermometer is sensitive to heat, so it can accurately measure the temperature and inform a computer chip of the reading. Digital thermometers, often used for medical readings, are the most accurate way to check a person's body temperature to determine if they are sick.

How does a digital thermometer work?

When the temperature changes, the sensor in the digital thermometer detects the difference in the electronic reading of the resistance (the part of the electrical circuit that limits the flow of electricity).

A change in this resistance becomes a temperature change. Digital temperature readings are shown as numbers on the display.

digital

The process takes about 30 seconds, which is very fast compared to a mercury thermometer as it takes 3 minutes to heat up and read!

Infrared thermometer

An infrared thermometer is a type of digital thermometer that can measure temperature from a distance. This can be used when the object to be measured is very weak or dangerous around it. Infrared thermometers can measure temperature from a few centimeters to kilometers.

How does an infrared thermometer work?

An infrared thermometer detects radiation from an object due to the object's molecules moving. The higher the temperature, the faster the molecules move and the more infrared they emit.

The radiant heat of an object is measured with an infrared thermometer and converted to heat. The heat is then converted to electricity and sent to a detector, which generates a number on the display indicating the temperature of the object.

This type of thermometer has been widely used during the COVID-19 pandemic to detect high temperatures from a distance so people don't stand too close.