🔬 Reverse Engineering the Reading: How IR Thermometers Work
Infrared (IR) thermometers provide instant, non-contact temperature readings, but how do they translate invisible energy into data? It all comes down to three key concepts:
1. Infrared Energy: The Invisible Signal
Infrared energy is a frequency of energy that sits outside the visable spectrum of light. However this energy is emitted by all objects.
When an IR thermometer targets a surface, it is designed to measure the intensity of the infrared wavelengths emitted by that surface. The hotter the object, the more intense the IR radiation it emits.
2. Emissivity: The Surface Factor
The amount of IR energy a surface emits is heavily influenced by its emissivity. This is a measure of a material's efficiency in emitting thermal energy.
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Low Emissivity (Highly Reflective): Surfaces that are polished or highly reflective reflect more IR energy from other sources and emit less of their own.
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High Emissivity (Non-Reflective): Dull or non-reflective objects absorb more energy and emit it more readily.
As a general rule, most non-metal surfaces have an emissivity of approximately 0.95. For maximum accuracy, it is essential to adjust your meter to the correct emissivity value for the material you are measuring. See our comprehensive Emissivity Guide below for specific material values.
3. Distance-to-Spot Ratio: Defining the Area
While IR meters are highly accurate, what exact area are they sampling? This is determined by the distance-to-spot ratio.
The distance-to-spot ratio relates to the distance between the meter and object to the diameter of the measured spot on the surface.
| Example Ratio | Distance | Measured Spot Diameter |
| 12:1 | 12 inches | 1 inch |
| 12:1 | 24 inches | 2 inches |
This ratio is critical: if you are too far away, you risk measuring a larger area than intended, potentially including surrounding (and cooler) objects. To ensure proper results, always observe the correct, sample distance, distance to spot ratio and emissivity settings.
*The above is guide only and values may vary
Testo 830-T2, 2 Laser Point Infrared (IR) Thermometer | IC-0560-8312
The IC-0560-8312 features a 12:1 Distance-to-Spot Ratio, ensuring you can accurately measure small targets from a safe distance. Its quick 2-second sampling time provides near-instantaneous surface temperature readings, minimising downtime on inspection routes.
This meter includes user-friendly features that enable rapid analysis and documentation. The Min./Max. Value Display allows you to instantly understand the temperature range of an area without manual data logging. You can also utilise the hold function to freeze the displayed value for easy note-taking, even in challenging environments.
Other features,
- Convenient one handed operation, with ergonomic gun type grip
- Visual and acoustic alarm if limit values are exceeded
- Option for contact measurement with additional temperature probe
HACCP Food Infrared & Probe Thermometer up to 330 Deg C | TCT303F
The TCT303F is an all-in-one temperature meter designed as a staple for food preparation and hospitality applications, ensuring both product consistency and safety compliance.
This meter combines the speed of an Infrared Thermometer for non-contact surface readings (ovens, hot plates) with a built-in fold-away probe for accurate internal food temperature measurement.
Other features,
- Rated IP67 to handle tough kitchen conditions
- Quick one second measuring response time for almost instantaneous results
- Integrated Safety System, Features a Go/No Go light system to provide immediate visual confirmation that food is safe to eat
Fluke 62 MAX IR Thermometer | FLUKE-62-MAX
The Fluke 62 MAX is engineered for industrial use, making it the most rugged and reliable mini IR thermometer available for professionals who work in challenging environments. It delivers the precise, repeatable measurements you expect from Fluke, combined with exceptional durability.
Key Features,
- Extreme Durability: IP54 rated for dust and water resistance while rugged enough to withstand a 3-meter drop test
- Precision Optics: Features a 10:1 Distance-to-Spot Ratio and precise laser technology for accurate, repeatable measurements of targets in the range of -30C to 500C
- Essential Data Functions: Includes Min/Max/Avg/Dif (Difference) display and Hi/Lo alarms to provide rapid data analysis and instant alerts for measurements outside of limits