Mike,

Thanks for the feedback. Another idea of mine that doesn't seem to be
working out. I did order the Fluke temp probe, but not the IR one. I
almost ordered the IR one but after reading your post I am glad I didn't. I
guess I will just use the probe for coffee and tea also.

Thanks
Russ
"mike" wrote in message
...
Russ wrote:
Mike,

Do you think any model will work or should I buy one of the expensive
ones? They have them from around $40.00 and up. It would be cool when
working on a pinball if I could point my thermal laser probe at all of
the transistors and find the one that isn't working.

Thanks
Russ

There are a bunch of issues.
The spot/distance ratio is critical. At the distance of measurement,
the spot size has to be small enough to measure just the thing you want.
But as it gets smaller, you have trouble aiming it. Even with a laser,
there's an offset that causes parallex error. The sense spot can't be
in the same place as the laser spot at all distances.

Emissivity relates to how well a particular material and surface treatment
radiates relative to a black body. Most cheapo units are
fixed at .95. More expensive ones have a calibration adjustment, but that
won't help if you don't know what to set it at.
Point it at a shiny aluminum heat sink and your reading won't be anywhere
near accurate. It's a relative measurement for similar materials only.

In most cases, you have no idea what 'normal' temperature is.
You can't tell if the problem is the device, a loose mounting bolt,
something else causing the overheat.

"back in the day" story alert....

Once tried to measure the temperature of a circuit board with an early IR
video scanner. Result was dismal because of the widly varying
emissivities.
Sprayed the whole board with spray-on foot powder.
Worked great cause it normalized emissivity.
Problem was that I couldn't wash the stuff of when I was done.
Ended up scrapping the board...very expensive temperature test.

Bottom line,
I use mine more to check the temperature of my coffee when I nuke it prior
to pouring it into the thermos. Fun toy, but relatively little used in
electronic diagnostics.
mike


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