Have you ever wondered whether your thermal camera actually gives you the correct measurement of temperature?
A thermal camera with 160x 120 pixels or less will normally give a correct measurement, but only up to about 5 or 7 meters against a target or spot size of 30 mm with a standard 15 mm lens
More advanced cameras have the option to enhance the range by adapting a tele-lens (70 mm)
First of all, do not be impressed by the visual improvement, you can see the problem, but how true is your measurement?
A tele-lens zooms in on your target and improves your visibility to see a problem. Despite this however, it still doesn't display the correct temperature.
The accuracy of your temperature reading depends on your 'detector spot ratio' (radiometric measurement).
In most cases, the manufacturers of the thermal camera often don't disclose the measurement ratio in their specification sheets.
You can usually rely on your thermal camera with a tele-lens for long distance applications; like searching for a hot spot on electrical contacts (30 mm spot size) on overhead transmissions and distribution lines (30 mm spot size) but if you need the true reading of temperature, you need a long range, high ratio IR thermometers such as Irtek LR 300 (up to 15 meters), LR 500 (up to 35 m) or LR 1500 (up to 80 m).
However, it would be ideal if you can afford to have the combination.