Temp probe for troubleshooting

This doesn't seem to be particulalry useful unless you have a reverence thermal map of a working unit. Some parts run hotter than others under normal conditions. And, what is going on in the electronics will also affect the heat generated.

Any significant overheating will be obvious to a reasonably well calibrated finger.

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Might wanna be careful about sticking that well calibrated finger into an off-line switching power supply...or Horizontal Output Transistor. I'll use my IR probe, thank you.

You might find other uses for an IR probe. I use mine to find heat leaks in the house, in cooking, auto repair etc. Handy little gadgets. mike

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Mike,

Do you th>> "Russ" writes:

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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Mike,

Thanks for the feedback. Another idea of m>> Mike,

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"Russ" bravely wrote to "All" (22 Apr 05 06:56:36) --- on the heady topic of "Re: Temp probe for troubleshooting"

Ru> From: "Russ" Ru> Xref: aeinews sci.electronics.repair:46218

Ru> A few times the finger thing worked real well for me. One was a Ru> pinball transistor It was so hot it burned my finger. I guess I was Ru> wondering if something more sensitive would be helpfull.

A wax crayon... Wax melts just under the boiling point of water around

180-200'F. IIRC there are even special wax mixtures calibrated for specific temperatures. These are used to calibrate furnaces, ovens, etc.

Many ceramic capacitors are highly sensitive to radiant heat and their capacitance value will drift according to temperature. When used in a bridge or a counter even the heat from a hand can be readily detected.

IR diodes are also sensitive to radiant heat but have to be compared to a known temperature.

A*s*i*m*o*v

... 'Keep the smoke inside.' -- 1st Rule of Electronics.