Re: anybody use infrared thermometers to check car?

Dec 08, 2010 3 Replies
E


I took my car to radiator service, and they had one of


> those infra-red remote thermometers with laser sights.
> So they could measure the temperature of the bottom
> radiator hose, transmission oil cooler and all sorts of
> stuff. I thought of getting one. It seems the good ones
> (with accuracy of 0.75 Celsius) are about $200.
> Any DIY car enthusiasts got one in their back shed?
>

I just picked up one of these units. I couldn't resist the sale at $19. Lots of uses around the house at this time of the year in finding air leaks, and checking out the cooling system on the old car. Can anyone shed some light on the theory behind what makes it work. I know that it measures the electromagnetic radiation coming from the surface aimed at to determine the temperature. I don't see how it works when the object surface is made of wood. Any takers?

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J

wood is not a good conductor, hence it's temperature to the touch always seems different from surroundings, but it'll be at ambient temperature if left alone, and thus emit radiation just the same as everything else.

the unit's sensor is just a "single pixel" sensor like those listed here:

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that does math based on black body radiation.

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the higher the temperature, the shorter the wavelength emitted.

presumably your reader assumes fixed emissivity. if so, this might help you get more accurate readings:

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P

Those IR thermometers are particularly good for quick tire temp checks when stopping for fuel on a long tow. They are also quite useful in the kitchen for the many applications where the surface temperature is sufficient, such as stirred liquids, and unlike probe thermometers they don't require cleaning after use.

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E

Solid info. Just what I was looking for. My search of Wiki was lousy. Thanks a bunch.

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