yes the infrared scanner have to be calibrated for the colour surface. I can't remember what the term is called but for dark surface we use a different coefficient compensation. For light surface, we use another coefficient factor to compensate for a more reliable reading.
For a metal surface that is hot, you would most probably get a red spot on the monitor screen with a temperature showing 40 deg plus.
Infrared scanner have been used widely in the power industry. They have been used to check for hot spot on high tension transformers and high tension line.
Loose connection on electrical installation have always been a problem in our power industry. It generate heat and will cause the connection to burn. Other than physically off the supply and retighten the connection, there is no way to do this. For high tension line, you can install the infrared scanner on a helicopter. By recording the images when the helicopter flied over the high tension cable, the data can be analysed later to determine any loose joint/connection.
and IR scanner cannot penetrate metal. The waveform is not ultrasonic.
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