digital thermometer measuring 36.2 degrees celcius

9 Common Measuring Tools For Temperature

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Last updated on September 4th, 2023 at 03:53 pm

Recent world events remind us that accurate thermometer readings of human temperatures are critical to effective diagnoses. Those who enjoy time in the kitchen also know that precise thermometer readings can be the difference between a healthy meal and food poisoning.

The comparison below can help you better understand the function and uses of different temperature-measuring tools.

1. Thermometer

A thermometer is a glass tube that may contain mercury. Many modern thermometers that don’t include a digital readout contain alcohol or another chemical that expands when heated.

As the temperature impacting the bulb increases, the product inside the glass tube expands, and the reading changes. 

Traditional thermometers are practical, but they can be time-consuming to use and difficult to read. Additionally, conventional thermometers that need to be placed under the tongue can be dangerous for children and impacted by the temperature of the food and drink you’ve recently taken in.

glass thermometer with a sunny sky as a background

2. Digital thermometer

A digital thermometer can be placed in the mouth, under the arm, or in the ear. In addition to getting an effective and accurate reading, these thermometers don’t contain toxins. They read the temperature via an electronic sensor and give a clear reading on the display screen.

For example, you can find digital thermometers that read human fevers and meat’s internal cooking temperature on your grill.

Carefully review the instructions on your digital thermometer, especially if you’re using one to check the temperature of meat on the grill. Your most accurate readings can only be counted on after a certain number of seconds.

Leaving a thermometer in the meat long-term may lead to dangerous inaccuracies.

holding a digital thermometer reading 37.0 celcius

3. Infrared thermometer

An infrared thermometer scans a surface and reports results without having to make any contact at all. These thermometers have become extremely popular since the COVID-19 outbreak of 2020.

For example, your dentist may require you to come in masked and scan your forehead before you can be treated. Because a fever can indicate that you are a risk to other patients and office staff, this scan from a distance is critical to public health.

Such thermometers can also be used to have significant effects in industrial applications. For example, large copper pots, often used in industrial cooking and brewing, can easily be scanned by an infrared thermometer to ensure the safest temperature range has been met.

However, it should be noted that these are surface scans. An infrared thermometer cannot safely read containers with an insulating layer.

woman wearing a mask using infrared thermometer to check temperature of a woman wearing a mask

4. Liquid crystal thermometer

A liquid crystal thermometer is used to gauge the temperature of a surface. If you have ever used a forehead strip to check a child’s temperature, you may have waited for the black crystals to change color and give you an effective reading.

It should be noted that liquid crystal thermometers check the surface temperature rather than the internal temperature. These tools are also quite popular among home brewers and those that need to maintain a steady internal temperature of a cooking pot, such as those culturing their own yogurt. 

As a general rule, it is recommended that these tools be used in conjunction with another thermostat for checking body temperature, as they could be more accurate.

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For example, a high fever, read by a liquid crystal thermometer in a forehead strip, could indicate a much more dangerous situation.

It’s also common for these thermometers to be used to measure water temperature in a fish tank. These strips can easily be stuck on the outside of the aquarium glass and the change in color will represent the water temperature.

liquid crystal thermometer on a glass aquarium

5. Thermocouples

Thermocouples include the connection of 2 different types of metal. When heat passes from one metal to the next, an electric charge is created, and a reading is produced. Thermocouples are often used in applications that humans cannot safely access, such as industrial ovens.

Because the reading is of an electrical charge rather than an actual temperature, thermocouple temperature sensors can be used over a long distance.

For example, the readings gained from thermocouples can reduce the risk of foodborne illness in cooking and cleaning industrial ovens. Industrial food production that requires in-place cleaning, such as large mixing containers, can also be checked via thermocouple data.

thermocouple in heater

6. Resistance Temperature Detectors

To make a resistance temperature detector, you must work with a metal with either very little or no resistance at a stable temperature. As the temperature changes, the resistance of the metal changes.

Most resistance temperature detectors are made of platinum wire wrapped around another metal. These detectors are highly effective in industrial applications requiring high and low-temperature readings.

In applications that humans cannot safely get to for an accurate measure, the readings off of a resistance temperature detector can provide a safe data set.

Resistance temperature detector isolated on white. With clipping path
Resistance temperature detector isolated on white. With clipping path

7. Bimetallic Thermometers

A bimetallic thermometer measures temperature by tracking the flex or warping of each metal within the thermometer. Because both metals inside the thermometer have a different response to heat, the measuring tool checks the difference between the curves of the two metals and generates a reading.

These measuring tools are often used by those who grill or smoke meat and need to take an extended reading to ensure that the ultimately required temperature has been met over time.

The gauges on bimetallic thermometers are generally round, and they often feature a needle or piercing tool to get a deep reading of the item to be measured.

bimetallic thermometer - meat probe

8. Infrared Pyrometers

Pyrometers use the visual radiation generated by a hot object to get an accurate reading of the surface temperature. Because these tools don’t need to be applied to the object itself, they can be used in situations that could include risk.

For example, pyrometers are used to read the temperature of the air at the top of a hot air balloon. They are also used to read the surface temp of a boiler that may become dangerous over time.

These tools are pretty expensive, but they can mean the difference between life and death in the proper application.

infrared pyrometer measuring temperature of car engine

9. Thermal imaging cameras

Thermal imaging cameras can be used to find risks inside structures. For example, if a fire alarm is sounded, but no fire is visible, professionals can find the source of the alarm with a thermal imaging camera.

Likewise, if a structure suffers from a water leak, a thermal imaging camera can see the cool spots evaporation creates. Pest professionals can also use these tools to find animals that don’t belong and set the right traps.

chipmunk thermal image

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