Choosing the correct thermal imaging camera

Edited by the Engineeringtalk editorial team Jun 15, 2006

Probably the most important factor in choosing a thermal imaging camera is price, but this should not be the only criterion, says Impac Infrared Sales Manager Dennis Smith.

Buying a camera on price alone will almost certainly drive the buyer into selecting a low resolution, 160 x 120 pixel (or smaller) array model.

In many cases the user would quickly come to realise that important details were missing whilst performing thermography.

However the market is changing rapidly and now high-resolution 320 x 240 pixel cameras are available at prices not much higher than the low-resolution models, giving the buyer a better choice.

The next question of course is "why is high resolution important in thermal imaging?".

The answer: pixels are the data acquisition points for thermal measurement and are used to create a visual image from the thermal profile.

More pixels provide a more accurate thermal interpretation and higher resolution of the thermal image.

High-resolution is particularly important since it allows identification of smaller details in the image and consequently more accurate temperature measurements.

To make thermal imaging cameras more affordable to a wider market, many suppliers have introduced detectors with pixel counts of 160 x 120 and smaller, with or without interpolation.

However, their resolution is at best only one quarter that of a 320 x 240 detector, ie 19,200 pixel compared with 76,800 pixel.

These larger detectors produce images twice as wide and twice as high, with four times the data for the same field of view.

High-resolution cameras also allow users to work much farther away from a target without losing measurement accuracy.

To achieve good temperature measurement a target must cover at least 3 x 3 (9) pixel to be accurately resolved, otherwise the measurement will only be an average of the target and the background.

Low-resolution detectors interpolate a greater area between pixels and averages in temperature readings unrelated to the target.

For example, the temperature of a target can be measured as accurately at a distance of 10 metres by a camera with 320 x 240 pixel as a camera with a 160 x 120 detector at 5 metres.

Resolution in thermal imaging cameras affects temperature measurement accuracy, not just the visual image quality - a point often overlooked in choosing a camera.

A 320 x 240 detector with 76,800 temperature-measuring points can resolve an area of just 3mm x 3mm at a distance of 2 metres compared with a 160 x 120 detector, with just 19,200 pixel can only resolve an area twice this size.

Plus, with more background averaged into the temperature readings, the measurements are inherently less accurate.

In conclusion buying on price may not be the best solution, particularly if accurate temperature measurement is an important factor.

It may be better to spend a little more to get the performance offered by a high-resolution camera.

Impac Infrared specialises in temperature measurement and consequently only offers high-resolution thermal imaging cameras.

With a choice of two portable models, the IVN 770-P and the IVN 320-P, the user can be assured of clear images and accurate temperature measurements.

In particular the new IVN 770-P represents a breakthrough in the cost of a high-resolution thermal imaging camera, offering high performance at a price similar to a low-resolution camera.

With a temperature range of -20 to +250C and onboard storage of up to 400 thermal images, the IVN 770-P is the ideal camera for both process and maintenance engineers.