How Does a Thermometer Measure Temperature (Best of 2024)

Do you know how a thermometer measures temperature? A thermometer measures temperature through a glass tube sealed with mercury that expands or contracts because the temperature rises or falls.

How Does a Thermometer Measure Temperature

The tiny size of the bulb and micro-fine size of the tube help the mercury reach the temperature of what it’s measuring very rapidly.

Bulb Thermometers: Follow the straightforward principle that liquids change their volumes relative to their temperature. As temperatures rise, the mercury-filled bulb expands into the capillary.

Its rate of expansion is calibrated on the glass scale. Two different scales are often found on thermometers–the Fahrenheit scale and therefore the Celsius scale.

With the Fahrenheit scale, Daniel Fahrenheit decided that the freezing and boiling points of water would be separated by 180 degrees and he pegged freezing water at 32 degrees.

Thermometer Measure Temperature

A thermometer is a device used to measure temperature. It works by detecting changes in temperature and converting them into a numerical value, typically displayed on a digital or analog readout.

Different types of thermometers work based on different principles. For example, a mercury thermometer works by using the expansion and contraction of mercury in a glass tube to measure temperature, while a digital thermometer uses a temperature sensor and converts the detected temperature into a numerical value that can be displayed on a screen.

Temperature is a measure of the degree of heat or coldness of an object or substance and is typically measured in degrees Celsius (°C) or Fahrenheit (°F). Thermometers are used in a wide variety of applications, from measuring body temperature in medical settings to measuring the temperature of food during cooking to monitoring the temperature of industrial processes.

How Does a Thermometer Measure Temperature

So he made a thermometer, stuck it in freezing water, and marked the extent of the mercury on the glass as 32 degrees. Then he stuck an equivalent thermometer in boiling water and marked it 212 degrees. He then put 180 evenly spaced marks between those two points.

On the Celsius scale, Celsius decided that the freezing and boiling points of water would be separated by 100 degrees and he made the melting point of water at 100 degrees.

Bulb thermometers are most ordinarily found in two places outside on our porches measuring the temperatures outside or under our tongues measuring our bodily temperatures.

With the age, the technology came the invention of other sorts of thermometers. Each different sort of thermometer has its distinctive means of measuring or controlling temperature.

For instance, electrical device thermometers are extremely effective for controlling temperatures. Although bulb thermometers are good for measuring temperature accurately, they’re harder to take care of set temperatures.

While bulb thermometers measure our changing temperatures once we feel feverish, electrical device thermometers help us bake our favorite cakes by maintaining a group temperature in ovens.

Recent technology has created new ways to live temperatures with electronics. This sensor changes its resistance with temperature changes.

A computer or other electronic circuit measures the resistance and converts it to a temperature, either to display it or to make decisions about turning something on or off. Read how a thermometer measures temperature.

Why Should I Take My Temperature?

Checking your body’s temperature with a thermometer is simple thanks to seeing if a fever is present. Though fevers are often uncomfortable, they’re a symbol that the body is fighting off infection.

There are many various sorts of thermometers you’ll use to live temperature. When using any quiet thermometer, confirm you read and follow the instructions that accompany the thermometer.

If your thermometer uses batteries, check them. You might notice that weak batteries give inconsistent readings.

What is a Normal Body Temperature?

Normal blood heat is about 98.6 degrees Fahrenheit (°F) or 37 degrees Celsius (°C). The normal temperature often varies from 1° to 2°F (½° to 1°C).

A normal temperature is typically lower in the morning and increases during the day. It reaches its height in the late afternoon or evening.

What Temperature is Considered a Fever?

You can treat this at home with a fever reducer medication and fluids to make yourself more comfortable, or let it run its course. But if it reaches 102°F (38.8°C) or higher and home treatment doesn’t lower it, call your healthcare provider.

How Do I Take a Temperature with a Thermometer?

Using a Digital Oral Thermometer

1. Wash your hands with soap and warm water

2. Do not eat or drink anything for at least five minutes before you take your temperature because the temperature of the food or beverage could make the reading inaccurate. You should keep your mouth closed at this point

3. Place the thermometer tip under the tongue

4. Hold the thermometer within the same spot for about 40 seconds

5. Readings will continue to increase and the F (or C) symbol will flash during the measurement

6. If you’re keeping track, record the temperature and thus the time

7. Rinse the thermometer in cold water, clean it with alcohol and rinse again

How Often Should I Take My Temperature?

If you’re feeling ill or if your child seems to be ill, it’s likely that you simply will reach for your thermometer. Often one of the first questions a health provider asks is if you’ve taken the temperature of the one that’s ill. You may decide to take medicine to reduce fever.

If you do, there’s usually a period of your time on the instructions about when it’s safe to require the drugs again.

However, if the primary temperature is extremely high, you would possibly plan to recheck the temperature on a more regular schedule, maybe once or twice an hour.

You might decide to recheck temperatures when medicine doesn’t seem to be working, like when the illness isn’t recuperating, and you still have symptoms.

Your healthcare provider might recommend times to need your temperature, like mornings and evenings. You should keep a record of those temperatures to be ready to report back.


Q: How does a thermometer work?

A: A thermometer works by measuring the temperature of an object or substance by using a physical property that changes with temperature, such as the expansion or contraction of a liquid or a metal.

Q: What is the most common type of thermometer?

A: The most common type of thermometer is a digital thermometer, which uses electronic sensors to measure temperature.

Q: What is a mercury thermometer?

A: A mercury thermometer is a type of thermometer that uses mercury, a liquid metal, to measure temperature. The mercury expands or contracts as the temperature changes, which is then measured and displayed on a scale.

Q: Why are mercury thermometers not used anymore?

A: Mercury thermometers are not used anymore because mercury is a toxic substance that can be harmful to both humans and the environment.

Q: What is a non-contact infrared thermometer?

A: A non-contact infrared thermometer measures temperature from a distance by detecting the infrared radiation emitted by an object.

Q: How accurate are thermometers?

A: The accuracy of a thermometer depends on the type of thermometer and the calibration of the instrument. Generally, most thermometers have an accuracy of within one degree Celsius or Fahrenheit.

Q: What is the temperature range that a thermometer can measure?

A: The temperature range that a thermometer can measure depends on the type of thermometer. Some thermometers can measure temperatures from below freezing-to hundreds or even thousands of degrees Celsius.

Q: How do you calibrate a thermometer?

A: To calibrate a thermometer, it is necessary to compare its readings to a known standard, such as a thermometer that has been calibrated by a laboratory. If the thermometer’s readings are off, it may need to be adjusted or recalibrated.

Q: Can thermometers be used to measure the temperature of gases?

A: Yes, thermometers can be used to measure the temperature of gases as well as liquids and solids. However, different types of thermometers may be required depending on the specific properties of the gas being measured.


A thermometer measures temperature by detecting changes in the physical properties of a material, such as the expansion or contraction of a liquid or gas. This change in physical properties is then converted into a numerical value on a scale that is calibrated to represent temperature.

The most common types of thermometers are liquid-in-glass thermometers and digital thermometers. Regardless of the type, all thermometers rely on the principle of thermal expansion and contraction to accurately measure temperature.

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