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Infrared (IR) thermometers have become an essential tool in industries ranging from manufacturing and food processing to electrical maintenance and HVAC service. Their biggest advantage? The ability to measure temperature from a safe distance without physically touching the object.
However, one critical factor determines how accurate those measurements will be: emissivity. Understanding emissivity and how to set it correctly in your IR thermometer is the key to getting precise results every time.
If you’re in the market for a high-quality non-contact thermometer, check out our Infrared Thermometer category, which includes models such as the Fluke 62 MAX+ IR Thermometer that allow adjustable emissivity settings for better accuracy across different materials.
What is Emissivity?
Emissivity is a measure of how effectively an object emits infrared energy compared to a perfect blackbody (which has an emissivity value of 1.0). It is expressed as a decimal between 0 and 1.
High emissivity (close to 1.0) – Materials like wood, water, and painted surfaces emit IR energy efficiently.
Low emissivity (close to 0.0) – Shiny or reflective materials like polished metals emit IR energy poorly.
An IR thermometer works by detecting emitted IR radiation and converting it into a temperature reading. If the emissivity is set incorrectly, the temperature reading will be inaccurate.
Why Emissivity Matters in IR Thermometry
The accuracy of non-contact temperature measurements depends on setting the emissivity value in the thermometer to match the material you’re measuring.
For example:
Measuring stainless steel at a default emissivity of 0.95 can lead to readings that are tens of degrees off.
Measuring a matte painted surface at 0.95 will likely produce accurate results.
Failing to adjust for emissivity can result in incorrect data, potentially leading to poor quality control, wasted materials, or safety hazards.
Common Emissivity Values for Materials
| Material | Typical Emissivity |
|---|---|
| Human skin | 0.98 |
| Wood (painted) | 0.90 – 0.95 |
| Aluminum (polished) | 0.05 – 0.10 |
| Stainless steel (polished) | 0.10 – 0.20 |
| Rubber | 0.90 – 0.95 |
| Glass | 0.85 – 0.95 |
Tip: Always refer to your IR thermometer’s manual and the material’s actual surface condition before setting emissivity.
How to Adjust for Emissivity in IR Thermometers
Check the manufacturer’s material emissivity chart – Many IR thermometers include a quick reference guide.
Use an adjustable-emissivity IR thermometer – This feature allows you to fine-tune settings for different materials.
Apply emissivity tape or paint – For shiny or reflective surfaces, using a high-emissivity coating can improve measurement accuracy.
Measure a reference point – If possible, measure a part of the object with a known emissivity (like a matte painted spot) and use that reading for calibration.
Best Practices for IR Temperature Measurement
Avoid measuring at an angle – IR thermometers are most accurate when used perpendicular to the surface.
Stay within the D:S ratio – The Distance-to-Spot ratio indicates how far away you can be while still measuring accurately.
Keep the lens clean – Dust or smudges can block IR radiation, affecting readings.
Account for environmental factors – Steam, smoke, or dust in the air can interfere with measurements.
Choosing the Right IR Thermometer
When selecting an IR thermometer for professional use, look for:
Adjustable emissivity settings for different materials
High optical resolution (D:S ratio) for long-distance accuracy
Wide temperature range for diverse applications
Rugged design for industrial environments
A great example is the Fluke 62 MAX+ IR Thermometer, which offers adjustable emissivity, IP54-rated dust/water resistance, and excellent optical resolution. For more options, visit our Infrared Thermometer category.
Conclusion
Understanding and correctly setting emissivity is the key to accurate non-contact temperature measurement. Whether you’re monitoring machinery, checking HVAC systems, or ensuring food safety, the right IR thermometer with emissivity adjustment can save time, prevent costly mistakes, and improve quality control.
Explore our Infrared Thermometers to find the right model for your needs — and ensure your measurements are always on target.
