Using a Thermal Gun / Infrared Thermometer for electronics

I have a friend who is an auto mechanic. He said that his shop recently bought a Thermal Gun, also called an Infared thermometer. He said it's quite handy, where it will detect coolant leaks, overheated parts of an engine, and even finds something like a hot connection in the wiring under a dashboard, and much more.

He is an expert with mechanics and has been in the business for over 30 years. He can repair auto wiring, but said he would not know the difference between a transistor or capacitor inside a car radio. Said he never learned electronics, just wiring.

Anyhow, I was telling him about my recent incident working on a preamp, and nearly burning my finger on an overheated IC chip. Almost immediately he asked me if I had a Thermal Gun. I had never even hear of them, but he explained how they work and said that it might be good for looking for hot components in an electronics device, in fact he said the manual said something about using it for that purpose.

RIght away I was thinking Big Money, but he said that they can be bought for as little as $35, but they bought one for around $120 because it had more features.

I asked how it works and he said you just point it at different parts of an engine or at a bundle of wires, or run it along an exhaust pipe to find leaks, and so on. And said there are ways to adjust its sensitivity, and it will locate clogged portions of a radiator and many more things.

This sounds like something that might be real handy for electronics work. Have any of you ever used them in this manner? If you have, are they worth the price to buy them for use on electronics?

Reply to
oldschool
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I don't know how well they would work for electronic testing, but you can get them on ebay for about $ 10 and up. Most have laser pointers on them, but for close in work the laser does not point to exectally the heat source.

Search for infrared thermometer.

Reply to
Ralph Mowery

There are other things to look for. There are two common viewing angles. 8:1 and 12:1. That means at 8 inches distance, the spot size is 1 inch. There's usually a chart on the side of the thermometer showing the spot size at various distances. You can see a smaller spot, at a longer distance with 12:1. Although the only real difference is calibration and the lens, prices on 12:1 are much higher than the more common 8:1. There are also some pocket IR thermometers with 6:1, which I consider almost useless.

The problem with using these to troubleshoot electronics is that there's no way you can isolate a fairly small component with a large spot size. You end up measuring the temperature of everything around it. If you're looking for a hot component, you'll do better with a cheap thermistor probe into a DVM. It does work well for large components, like power transistors, heat sinks, xformers, big electrolytics, etc. I just used mine to isolate the area on the case of an overheating ASUS RT-N66U. Works well on the large case area.

Also, watch out for the operating temperature range. I like to use mine for cooking, measuring soldering iron tip temp, automobile engine temp, exhaust manifold temp, and wood burner temp.

I bought 3 of these a few weeks ago after my Sears IR thermometer self destructed. The picture shows the backlighting display changing from green-blue-red with setpoints. This is NOT included in the model 981C but is a feature of the 981D, which seems to be unavailable.

Like all such cheap devices, the laser pointer is misaligned. One thing I like about it is that it does NOT have a rubberized paint coating on the handle, and will therefore not self destruct like the Sears version, where the rubberized paint turned to sticky goo.

When not measuring temperature, it's also useful for playing with the cat, who likes to chase the red dot.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

I use a basic one often enough to require bypassing the button cells and wiring out to an external bigger battery

Reply to
N_Cook

I bought one for under $25 shipped and I've seen them cheaper. How cheap does it need to be to pick up one?

I've used it for any number of things including measuring the temperature of the sky which can be so low the unit doesn't read a number at all. Now that's cold!

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Rick C
Reply to
rickman

On Monday, May 8, 2017 at 10:47:44 AM UTC-4, Jeff Liebermann wrote: but is a feature of the 981D, which seems to be unavailable.

Being ordinarily cheap, I nonetheless tend to buy quality tools (I hate to spend money, but I hate having to spend twice even more). I use a Raytek R aynger ST, and according to it's label, it was built in 2000. I can't beli eve I've owned this that long. It's a 12:1 and it does have some sort of ru bberized grip, but it's still pliable with no sign of returning to it's ori ginal chemical state.

I use this often and never had a problem with it. If it ever dies, I'll ge t another Raytek assuming it's still made somewhere other than China (this one is U.S. made).

One thing a lot of people don't realize is that these work great, but won't work on reflective surfaces.

Reply to
ohger1s

It's not just reflective surfaces. The calibration of these things depends on the emissivity of the object being measured. Metallic surfaces are so low that they won't work at all, in fact, they reflect IR from the environment and so appear to read a valid number when they are just mimicking the environment. Other surfaces will read a lower temperature than accurate because their emissivity is lower than the unit is calibrated for.

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Rick C
Reply to
rickman

o spend money, but I hate having to spend twice even more). I use a Raytek Raynger ST, and according to it's label, it was built in 2000. I can't be lieve I've owned this that long. It's a 12:1 and it does have some sort of rubberized grip, but it's still pliable with no sign of returning to it's o riginal chemical state.

get another Raytek assuming it's still made somewhere other than China (thi s one is U.S. made).

't work on reflective surfaces.

Really? So if you waved it along a wall, it wouldn't let you know when a sh eet metal 2x4 was behind the wall or not? Or have you tried that?

Reply to
bruce2bowser

I had to figure out what y IR thermomometer would measure accurately by comparing measurements with an accurate thermometer that makes contact with the object or fluid being measured. I then amused myself for a little while measuring the temp of some aluminum surfaces. The reflected IR that you mentioned had me wondering for a bit because the temp indicated would change quite a bit depending on whether I was measuring the IR from the gas stove flame being reflected from the pot's surface into the IR sensor. Eric

Reply to
etpm

o spend money, but I hate having to spend twice even more). I use a Raytek Raynger ST, and according to it's label, it was built in 2000. I can't be lieve I've owned this that long. It's a 12:1 and it does have some sort of rubberized grip, but it's still pliable with no sign of returning to it's o riginal chemical state.

get another Raytek assuming it's still made somewhere other than China (thi s one is U.S. made).

't work on reflective surfaces.

Really? So if you waved it along a wall, it wouldn't let you know when a sh eet metal 2x4 was behind the wall or not? Or have you tried that?

Reply to
bruce2bowser

Google "cosmic microwave background"...

Mike.

Reply to
MJC

Hard to measure that with a thermal sensor. Too much air in the way. But on a clear night you get an average of sorts of the various layers of atmosphere and outer space.

That's a funny name, "outer space". We seem to have found names for all the atmosphere layers, I wonder why we didn't find a more formal name for outer space.

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Rick C
Reply to
rickman

This is a SEEK thermal picture of a quarter watt resistor dissipating a quarter watt. Background is 70F. Resistor is 113F according to the SEEK.

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You can see the heat conducted thru the wires into the alligator clips. There's also a slight temperature rise all along the cable to the power supply due to the 1/4 amp thru the wire.

On a dense surface mount board, you can easily tell if a part is getting hotter than the surroundings.

It'll cost you $200, but if your time is worth anything, it will quickly pay for itself.

If I pass my 12:1 IR temperature probe across the resistor, the highest reading I can get is 71F if I stick it as close as possible to the resistor. You really need the area being sensed to fill the whole field of view of the sensor. Pretty much useless for today's electronics.

The built-in laser pointer is useless for close up work. Parallax causes you to point to the wrong place.

Emissivity is a big deal if you want accurate temperature measurements. Back in the '80's, I used IR imagery to find shorts in prototype circuit boards. Ran some current thru the shorted traces. If you limited the voltage to something below half a volt, you couldn't hurt anything on the board. Most shorts were to one of the ground planes. I could see the inner layers and where the short was.

But, for accurate temperature measurements on a running system, I had to normalize the emissivity. Somebody suggested that spraying the board with spray-on foot powder would work. It worked great. But they forgot to tell me that you can't get the stuff off. I didn't have any solvents that could remove it without harming some components on the board. That limited its usefulness to destructive testing. ;-)

With the seek, you can find the shorted cap on your laptop board by putting a little current thru the power trace and see where the heat stops. I had one laptop that was driving me nutz. Turned out there was a cap hidden under some other component that was bad. It was a .1uF cap. Those rarely short. I would never have found it without the thermal imager.

If you're doing very hot or cold measurements, pay attention to the specs on your thermal device. Many have range limited to less than you need. My SEEK can easily see the heating element on my soldering iron, but the temperature readout is wrong. My 800F Weller reads 656F on the heating element and -40F on the tip. Below about 480F, it reads the element correctly against the background at 70F.

Reply to
mike

Are you sure that it's not reading the temperature of whatever is near the other ear?

(Sorry, I couldn't resist).

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

Lol, that's a good one!

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Rick C
Reply to
rickman

Thanks for all the good advice on IR guns and imagers.

Before IR imagers, I used a liquid crystal sheet. I have a small selection of various temperature ranges. Obviously, it won't work with non SMT PCB's that are full of "lumpy" components. While I can't really see individual tiny components, I can at least find hot spots. I used to call this my "poor mans" IR imager, except that liquid crystal sheets have gone up in price, while IR thermometers and imagers have gone down.

I have my finger on the buy it now button. Someone help me to resist the temptation.

Yep, and the further away you get, the worse the problem. For small parts, I use either a thermistor probe, or the cheap type K thermocouple probe that came with my DVM.

I once had a cheap IR thermometer that had two lasers. The idea is that it would bracket the spot allowing the user to better locate the spot. Unfortunately, this model had the lasers just as badly aligned as the models with a single laser. I ended up cracking the glue used to hold the lasers, and using hot melt glue to properly position them. Up close, the parallax problem made them useless, but at a distance, they were fine.

Nicely done. I'm still using the liquid crystal sheets, or putting the palm of my hand over sections of the PCB until I find the hot spot. However, I would never have found a shorted cap located under some other components.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

You can restrict the field of view with a straw. I haven't calibrated this approach, but it should work ok. The sensor element is very small and is at the base of a black cone which I believe is what establishes the field of view. As long as you are viewing hot items it shouldn't matter that the straw is not as black as the cone. Maybe I'll try this later if I can find my IR thermometer.

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Rick C
Reply to
rickman

Yes, that does work. It won't be accurate temperature, but you can tell relative temps if they're much hotter than ambient. Unless your straw is surrounded by a really good IR blocker, the radiation from the blockage might swamp the changes from the straw.

I once experimented with a PIR sensor attached to a an LED. I put a straw over the sensor to restrict the field of view. My expectation was that I could scan an area watching the LED and have my brain construct a rough image of what I was scanning. Alas, my brain was not up to the task. Then, I decided to rotate the assembly to scan a line and correct for angle and distance and put dots on the screen of my PDA according to position of the spinner and tilt of the whole assembly for the Y axis. Alas, my brain wasn't up to that task either.

Reply to
mike

If you wait more than four hours, you may have permanent damage.;-)

If it's the SEEK, make sure you're getting the right one with the variable focus. I prefer the narrower field of view to get more resolution up close, but that's a personal issue.

At the time I bought mine, I sent questions to all the cheap ebay vendors to verify that the one they were selling was the one I wanted. I never got a straight answer out of any of them. I expect they're all forwarders for a drop shipper somewhere and have never seen one up close. I decided to pay $20 more from a source that seemed more reputable...whatever that means. At least they gave me a straight answer that the were shipping the one I wanted. Can't remember who that was.

There were also warranty issues. If you didn't buy it directly from an approved SEEK reseller, the warranty was less or none at all.

A friend of mine dropped his 3 feet to the floor. A bunch of the bolometer stalks broke off. Looked like someone took a shotgun to the image. SEEK replaced it, no questions asked.

If your phone is on the supported list, you're good to go. Otherwise, it's a crap shoot. I use mine on a Motorola Moto G first generation. Also works on a Galaxy Note II Works on a ZTE Speed, but the connector is on the side, so difficult to get your head wrapped around what you're seeing. Fails on a Huawei Union (boost mobile $10 phone from Best Buy last year) even tho it has newer OS and passes the USB OTG test.

I'd do some googling to see if anyone commented on compatibility with your phone.

Reply to
mike

I have used one or more. I made a tube to cut down on beam width. You can get a pretty good idea of coverage. Reading may vary with reduced beam.

Greg

Reply to
gregz

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