Choosing a thermal imaging camera: resolution, temperature range, emissivity?
A thermal imaging camera makes surface temperatures visible and reveals faults before they cause a failure. Whether you inspect electrical installations, mechanical hot spots or insulation, the decisive factors are detector resolution, thermal sensitivity, temperature range and a correctly set emissivity. This guide explains the key selection criteria and shows how to avoid common measurement errors from reflections and emissivity.
Explore measurementWhat resolution and sensitivity does a thermal camera need?
The detector resolution defines how many temperature measuring points the thermal image contains - from 160x120 on entry-level units up to 640x480 in the top class. Equally important is thermal sensitivity (NETD): it states the smallest temperature difference the camera can still resolve clearly. The lower the NETD in mK, the finer the visible detail.
More pixels mean more real measuring points per image and therefore sharper contours from a greater distance. Look at the native detector resolution, not interpolated figures. For small parts the geometric resolution (IFOV) also matters: it sets how small a reliably measurable spot can be at a given distance.
- 160x120: entry level, overview and larger objects
- 320x240: standard for electrical and maintenance work
- 640x480: detail shots and measurement from a distance
- NETD < 40 mK: fine temperature contrasts stay visible
Which criteria decide the purchase?
Besides resolution and NETD, the temperature range, field of view and the ability to set emissivity and reflected temperature all count. Also check whether the camera reports only a single spot value or evaluates the whole image - full-image analysis finds hot spots that a single point misses. The table below sums up the key criteria.
Match the temperature range to the task: electrical inspections usually need -20 to 150 °C, while mechanical or process hot spots call for 500 °C and above. Too wide a range costs resolution in the window that actually matters.
How do I avoid errors from emissivity and reflections?
Every material emits heat differently. Emissivity describes this on a scale of 0.1 to 1.0 - matte, dark surfaces sit near 1.0, bare metals well below. A wrong emissivity setting distorts the reading directly. In addition, the reflected temperature must be corrected so mirrored heat sources do not spoil the result.
- Set emissivity to match the material, do not leave it at a blanket 0.95
- Capture and correct the reflected temperature (radiators, sun)
- Do not measure through glass or polished surfaces
- Aim close enough and perpendicular to the object
Frequently asked questions
What does resolution mean on a thermal camera?
It states how many individual temperature measuring points make up the image, such as 160x120 or 640x480. More pixels give sharper contours and allow measurement from a greater distance.
What is the NETD value?
NETD (Noise Equivalent Temperature Difference) describes thermal sensitivity - the smallest temperature difference the camera can still resolve. The lower the value in mK, the finer the detail.
Why does emissivity matter so much?
It determines how much heat radiation a material emits. If it is set wrong, the camera reads a false temperature. Bare metals need special care or a matte reference surface.
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