Infrared thermometers have revolutionized how we measure temperature in various settings, from industrial to culinary environments. Understanding how to use an infrared thermometer effectively is crucial for obtaining accurate temperature readings. These devices offer a non-contact means of measuring surface temperatures, providing safety and convenience, especially when traditional thermometers are impractical or unsafe. This guide aims to demystify the process, ensuring you can confidently use an infrared thermometer.

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How Infrared Thermometers Work?

Infrared thermometers work by detecting the infrared energy emitted by objects. Every object emits a certain amount of infrared energy based on its temperature, and these thermometers translate this energy into a temperature reading. Unlike traditional thermometers, infrared can measure surface temperatures without touching the object. This feature makes them particularly useful for measuring the temperature of objects that are either too hot, dangerous, or difficult to reach. However, it’s important to note that they measure surface temperatures only and do not gauge the internal temperature of an object.

Preparing to Use an Infrared Thermometer

Before you begin to use an infrared thermometer, there are a few preparatory steps to ensure accurate readings:

Understand Emissivity

Emissivity refers to the efficiency with which an object emits infrared energy. It’s crucial to be aware that different materials have different emissivity values, which can affect the accuracy of the temperature reading. Most infrared thermometers are calibrated to an emissivity of 0.95, which is suitable for measuring the temperature of most organic, oxidized, or painted surfaces. It’s advisable to use an infrared thermometer with an adjustable emissivity setting for reflective surfaces like metals.

Distance-to-Spot Ratio

This is the ratio of the distance from the thermometer to the object being measured to the size of the area being measured. Understanding this ratio is important to position the thermometer correctly for accurate readings.

Powering On and Setting Up

Power on your infrared thermometer and adjust the settings according to your requirements, such as switching between Celsius and Fahrenheit. Ensure the device’s lens is clean to measure surface temperatures accurately.

someone holding a thermometer over a pot

How to Use the Infrared Thermometer

  1. Aim Correctly: Point the infrared thermometer directly perpendicular to the surface of the object you’re measuring. This ensures that the area in the thermometer’s “snapshot” is a tight circle, leading to more accurate results.
  2. Distance and Spot Size: Maintain the appropriate distance between the thermometer and the object to ensure the spot size is suitable for the measurement. This is crucial for getting a precise temperature reading.
  3. Steady Measurement: Hold the infrared thermometer gun steadily and aim it at the area where you need the temperature reading. If measuring an oven temperature, ensure you’re measuring the surface, not the air temperature inside.
  4. Reading the Temperature: Once aimed correctly, press the trigger of the infrared thermometer. Wait for a few seconds as the device measures the surface temperature. Infrared thermometers measure quickly, providing a temperature reading on the display almost instantaneously.
  5. Interpreting Results: Remember that infrared thermometers measure surface temperature only. They do not provide information about the internal temperature of an object. If you need to measure internal temperatures, a different type of thermometer will be required.

What Temperatures Can Infrared Thermometers Measure?

Infrared thermometers are designed to measure a wide range of temperatures, primarily focusing on the surface temperatures of objects. Here’s a closer look at the specifics:

Surface Temperatures

The primary function of infrared thermometers is to measure the temperature of an object’s surface. They do this by detecting and measuring the infrared energy emitted by the object. The amount of infrared energy emitted directly relates to the object’s surface temperature.

Range of Temperatures

Infrared thermometers typically have a wide temperature measuring range. Many models can measure temperatures below freezing to several hundred degrees Celsius or Fahrenheit. This makes them suitable for various applications, from checking freezer temperatures to measuring the heat of cooking surfaces or industrial equipment.

Non-Contact Measurement

A key advantage of infrared thermometers is their ability to measure temperatures without coming into contact with the object. This is particularly useful for measuring high temperatures or surfaces that are difficult to reach or hazardous to touch.


While infrared thermometers are highly accurate for surface temperature measurements, it’s important to note that they cannot measure internal temperatures. For example, they can tell you the surface temperature of a pan or a pipe but not the internal temperature of food cooking in the pan or the fluid flowing through the pipe.

Environmental Influence

The accuracy of an infrared thermometer can be influenced by the environment in which it’s used. Factors like dust, smoke, fog, or the object’s emissivity can impact the accuracy of the temperature reading.

Cleaning and Maintenance

  1. Regular Cleaning: To maintain accuracy, clean your infrared thermometer gun regularly. Dust, dirt, and other contaminants can affect the precision of the temperature readings.
  2. Cleaning Materials: Use a soft cloth or cotton swab moistened with water or medical alcohol for cleaning. Avoid using soap or harsh chemicals as they might damage the lens.
  3. Cleaning Process: Gently wipe the lens first and then the body of the infrared thermometer. Ensure that the lens is completely dry before using the device again.
  4. Avoid Obstructions: Make sure the path between the infrared thermometer and the measured object is clear of obstructions like glass, liquids, or transparent surfaces. These materials can interfere with the infrared measurement.
  5. Storage: Store the infrared thermometer in a clean, dry place to prevent damage. Avoid exposure to extreme temperatures or moisture.

Calibrating Your Infrared Thermometer

Understanding Calibration

Calibration is essential to ensure that infrared thermometers work accurately. Over time, the infrared energy detection mechanism may drift, leading to less precise temperature readings. Regular calibration ensures that the thermometer can accurately measure temperatures.

Using a Calibrator or Known Temperature Source

You can use a blackbody calibrator or a known temperature source, like boiling water. The idea is to compare the thermometer’s reading with the exact temperature of the calibrator to check its accuracy.

Calibration Process

Aim at the calibrator or known temperature source to calibrate your infrared thermometer gun. Adjust the thermometer accordingly if there is a discrepancy between the known temperature and the thermometer’s reading. This may involve adjusting settings within the device to align with the known temperature.

Frequency of Calibration

The calibration frequency depends on how often and in what environments the IR thermometer is used. In environments with extreme temperatures or high levels of infrared radiation, more frequent calibration may be necessary.

Practical Tips and Common Mistakes

Using IR Thermometers Correctly

  • For accurate readings, ensure the lens is clean and free of any obstruction.
  • Be aware of the field of view of your IR thermometer to ensure you’re measuring the correct area.
  • Remember that infrared thermometers measure the surface temperature, not the internal temperature of objects. This is particularly important when measuring body temperature or the temperature of food items.

Avoiding Common Mistakes

  • Misunderstanding Emissivity: Emissivity settings are crucial for accurate temperature readings. Incorrect emissivity settings can lead to inaccurate readings, especially when measuring shiny or polished surfaces.
  • Ignoring Environmental Factors: The presence of infrared light, smoke, steam, or dust in the environment can affect the reading. Always account for these factors when using an IR thermometer.
  • Incorrect Angle of Measurement: Always aim the infrared thermometer gun directly perpendicular to the surface for a more accurate reading. Angled measurements can distort the object’s temperature reading.

mother checking her son's temperature

Verifying Accuracy

To ensure your thermometer provides accurate readings, periodically test it against a known temperature source, such as boiling water or an oven temperature, and adjust as necessary.

Handling and Maintenance

Handle the thermometer with care to avoid damage to its infrared sensor. Regular maintenance and cleaning are essential for reliable performance.

What Next?

Infrared thermometers are invaluable for quickly and safely measuring surface temperatures in various settings. You can significantly enhance their accuracy and reliability by understanding how these devices work and adhering to proper usage and maintenance practices. Regular calibration is essential to ensure that you’re getting precise readings. Additionally, knowing their limitations and common pitfalls can help avoid inaccuracies. When used correctly, infrared thermometers can provide fast and accurate temperature readings, making them a versatile and essential tool in many industries and applications.

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