Owen Duffy wrote:
On 4 Dec 2006 06:07:44 -0800, "Denny" wrote:

...
So I purchased an Infrared measurement gun...

fascinating little instrument - did you know that on a clear day with
the air temperature +12.1 F and zero wind, that a 5 foot diameter
black rubber tractor tire facing the clear sky to the North can have a
surface temp of -2.6 to -3.0 F? I didn't but that is what I found...
OK, I digress again

It is not such a digression.

You should do make measurements of the temperature of different
materials that you know are at the same temperature, and see what
results you get from your non-contact thermometer.

The emissivity of the surface is an important factor that limits the
absolute accuracy of these things.

It is an interesting experiment that you have described, though I am
not sure that surface temperature (if it is accurate) alone is a good
indicator of the power flow to the air. For example, would you expect
that the temperatures of natural coloured and black aluminium heatsink
to be the same if dissipating the same (non zero) power in the same
environment? Extending that to your experiment, is dark enamelled
copper wire (as may be used in a coil) a better black body radiator
than bright aluminium (as may be used in a capacitor).

Owen
--

And of course, the magnitude of the surface area over which the power is
being dissipated will also influence the temperature rise of the small
area being measured by the instrument.

Measured temperature differences of the same material and at the same
distance (under different experimental conditions) are likely to be more
accurate than absolute measurements with unknown emissivity.

Chuck

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