How Thermometers Work: An In-depth Look

Written By caroline

Caroline is a freelance science writer with a PhD in physical chemistry. She has a particular interest in the area of temperature measurement and has written extensively on the topic for a variety of science-focused websites. Kittens, lego, and barbeques are some of her other passions. She currently resides in Boulder, Colorado with her two cats.





Have you ever wondered how a thermometer works? It’s actually a fascinating phenomenon that can help us measure temperature easily and accurately. To truly understand how thermometers work, you must first know the different types of thermometers and how they measure temperature.

This article will take an in-depth look at thermometers, how their measurements work and what types of thermometers exist. Read on to find out everything you need to know about thermometers and how they help us to measure temperature.

How does a thermometer work?

Thermometers are instruments that measure temperature. When the tip of the thermometer touches the material it is measuring, heat energy travels through it and into the mercury contained inside. This causes the mercury to expand and turn into a liquid, driving it up the tube within the thermometer. As the mercury continues to rise up, you can take a reading of the temperature when it stops on the scale.

To understand this process better, let’s take a look at what happens in greater detail. First, when heat energy from the material is conducted to the mercury, the metal begins to change state from solid to liquid. This thermal energy warms up and vaporizes some of the mercury making it a gas, while some remains as a liquid.

As more vapor is produced and pressure builds up, it forces some of the liquid mercury up the tube in droplets. This liquid then condenses back into its solid state as it cools down again and eventually reaches an equilibrium where it settles on the scale.

The reading taken directly corresponds to the temperature of the material being measured. It goes without saying that thermometers must be used with accuracy and care to get precise readings from your environment.

Using a thermometer properly

  • Be sure to read any instructions that come with your thermometer for proper usage.
  • Don’t insert a thermometer into any area of your body or any other warm material without first consulting an expert.
  • Make sure not to move or shake your thermometer while taking your measurement since this can lead to errors in accuracy.
  • Make sure that both ends of your thermometer are clean before use. Place a cap on one end after each use.
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The Science of Forehead Temperature Taking

When determining your child’s temperature, a forehead thermometer is an effective and easy-to-use tool. To use it correctly, follow these steps:

  • Slowly slide the thermometer across the forehead, making sure to keep it in contact with the skin all along.
  • Continue moving it from the forehead towards the top of the ear, until you reach the hairline.
  • Read the temperature on the display screen when you’re finished.

A forehead thermometer reads infrared heat given off by a person’s temporal artery. This provides an accurate temperature reading in a short amount of time.

This type of thermometer does not require any physical contact with your child — which can be extremely beneficial for kids who do not like to have their mouths or armpits touched. Also, you don’t need to be concerned about sterilizing tips or accidental contact with air.

The modern forehead thermometer has several advantages over old-fashioned mercury thermometers: they’re quick and accurate, emitting no hazardous material, they are equipped with fever alert indicators, and they come in multiple varieties such as digital displays or printed readouts.

By following the simple three-step procedure outlined above, you can use a forehead thermometer to read your child’s temperature easily and accurately without having to worry about any health risks.

how does a thermometer work

Measuring Temperature: A Quick Answer

Temperature is an important indicator of our health, so knowing how to take it correctly is essential for accurate readings. Depending on the age and size of the person, there are different methods for measuring their temperature.

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Mouth: For adults, the best practice is to place the probe under the tongue and close the mouth. It’s important to avoid breathing during this time, so breathing through the nose is recommended.

Rectum: This method should only be used on infants and small children, since they are unable to hold the thermometer safely in their mouths. It involves gently inserting a thermometer into the rectum.

Armpit: Taking a temperature reading under the arm is also a common way to check temperature. To ensure accuracy, it’s important to place it in the armpit and press the arm against the body while taking a reading.

In summary:

  • Mouth. Place the probe under the tongue and breathe through the nose.
  • Rectum. Use for infants and children who cannot hold a thermometer safely in their mouths.
  • Armpit. Place the thermometer in the armpit and press arm against the body.

Thermometers: 4 Variations to Master

If you are looking for the best way to measure someone’s temperature, one of the four types of thermometers can offer an ideal solution. From digital thermometers to infrared thermometers, there is a wide range of options available for home use.

Digital Thermometers are contact thermometers that measure temperature by reading heat from the forehead, armpit or mouth. They typically provide quick readings and can be used in infants, children and adults.

Ear Thermometers use infrared technology to detect heat generated by the eardrum and surrounding tissues. This type of thermometer is recommended for use in infants aged 6 months or older and older children.

Strip Thermometers detect heat emitted by the skin on the forehead. Easy to operate and convenient to use, this type of thermometer is an ideal option for children who may not be able to stand still while having their temperature taken.

Infrared Thermometers read temperature from the ear or forehead without any physical contact. While these thermometers provide accurate readings for all ages, they are particularly suitable for very young infants.

When selecting a thermometer, consider what age group it is suited for and what situation it will be used in. Depending on your needs, one of these four types of thermometers that could be suitable.

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What’s Inside a Thermometer – You’ll Be Surprised!

In the average mercury thermometer, you will find a small, silvery ball. Although mercury can be found in many everyday objects, it is hazardous if handled improperly. If a thermometer breaks and the mercury is not cleaned up correctly, it can evaporate and contaminate the air.

This vapor is toxic to humans and other wildlife. Each mercury thermometer typically contains anywhere between .5-1.5 grams of mercury. This small amount of mercury is the reason why proper disposal or clean-up is essential in the event of any breakage.

Mercury is often used for thermometers because it has a relatively low boiling temperature so it does not require much heat for evaporation and will quickly reach equilibrium in different temperatures. Additionally, mercury does not corrode or mix with other substances due to its non-reactive nature.

When dealing with any kind of mercury thermometer, safety should always be paramount. Dispose of expired thermometers properly and keep in mind that minor breakages should be immediately cleaned up. To protect yourself and your environment always take the extra time to dispose of hazardous material properly.

If you use a analog thermometer either for work or at home, make sure to read and follow all instructions thoroughly.

Mercury Thermometers Safety Tips:

  • Read all instructions thoroughly before handling any mercury thermometers.
  • If a thermometer breaks, immediately clean up any spills while wearing protective gear such as gloves and goggles.
  • Dispose of expired thermometers properly according to state laws.
  • Contact your local hazardous waste \recycling specialist for help with disposal if needed