Cheap ir thermometer for transistor checking?

[Solder_Junkie]

Apologies if this has already been asked, but are the low cost ir thermometers much use to check for overheating transistors? As far as I can ascertain, they are prone to averaging the temperature within their "viewing" cone, and while OK to measure something fairly large, such as a large heatsink, they are probably too broad to be reliable to check individual transistors.

I don't want to spend a huge amount, so am not looking for a thermal imaging camera. Would a Fluke 62, one of the many cheap Chinese units, be any use with through hole (TO92 and similar sized) transistors, or would it be money wasted?

[Kleinstein]

You named the problem: it's the viewing cone. So the important factor is the question how close you can get to the tip of the cone. The actual sensor is usually quite small, something like 2 mm diameter. How close you can get depends - some units use a sparate plastics lense and are this of no real use for anything smaller than TO3. Its actually those with a larger viewing angle where you have a better chance to get a really local reading.

Some in ear thermometers could work, if they also work in a larger than the small medical range.

[SeanB]

I bought the cheap in ear one ( $20) and it will do from -20C to 120C with reduced accuracy. Plenty good enough to see if a package is overheating, as no semiconductor package should be over 70C in any case for reliability. Over 100C it is being run way too close to cook.

[Solder_Junkie]

Thanks for the replies. I think I'll try one of the cheap Chinese ir thermometers from eBay that go to 500C or so. For less than 15 GBP they might be useful for other purposes if they struggle to measure small transistors up close.

The Fluke 62 Max+ looks interesting, but I'm not sure if the laser pointers are much benefit at half an inch range, so I'll save my pennies.

The ear thermometers I can find only specify limited temperature ranges and might not display outside "body temperatures", but thanks for the idea Sean.

[SeanB]

The cheap in ear ones use the same bolometer as the cheap IR ones, just that during manufacture of the bolometers they test them all, and those with good accuracy at 30-40C are marked as the in ear ones, the rest are graded into looser selections and the ones that are still functional but really poor go into the cheap IR guns. The more expensive IR sensors are used in the expensive units, where they actually come with a cal certificate and with a compensation table for the sensor built in.