Using a Thermal Gun / Infrared Thermometer for electronics

[olds...@tubes.com]

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?

[Ralph Mowery]

In article <j370hc5nbfnvqp1mu...@4ax.com>,
olds...@tubes.com says...

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.

[Jeff Liebermann]

On Mon, 8 May 2017 10:00:00 -0400, Ralph Mowery
<rmower...@earthlink.net> wrote:

>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.

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.
<http://www.ebay.com/itm/222404502261>
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.

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[N_Cook]

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

[rickman]

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!

--

Rick C

[ohg...@gmail.com]

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.
>
> 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.

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 Raynger ST, and according to it's label, it was built in 2000. I can't believe 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 original chemical state.

I use this often and never had a problem with it. If it ever dies, I'll get 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.

[rickman]

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.

I can put mine up to my ear canal and read 96 °F.

--

Rick C

[et...@whidbey.com]

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

[bruce2...@gmail.com]

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

[MJC]

In article <oeq2tm$77p$1...@dont-email.me>, gnu...@gmail.com says...

>
> 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!

Google "cosmic microwave background"...

Mike.

[rickman]

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.

--

Rick C

[mike]

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.

http://i.imgur.com/jmDIdQb.jpg

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.

[Jeff Liebermann]

On Mon, 8 May 2017 11:46:44 -0400, rickman <gnu...@gmail.com> wrote:

>I can put mine up to my ear canal and read 96 °F.

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

(Sorry, I couldn't resist).

[rickman]

On 5/8/2017 9:39 PM, Jeff Liebermann wrote:
> On Mon, 8 May 2017 11:46:44 -0400, rickman <gnu...@gmail.com> wrote:
>
>> I can put mine up to my ear canal and read 96 °F.
>
> Are you sure that it's not reading the temperature of whatever is near
> the other ear?
>
> (Sorry, I couldn't resist).

Lol, that's a good one!

--

Rick C

[Jeff Liebermann]

On Mon, 08 May 2017 17:19:50 -0700, mike <ham...@netzero.net> wrote:

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

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

Before IR imagers, I used a liquid crystal sheet.
<https://www.teachersource.com/product/292/chemistry>
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.

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

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

>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.

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.

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

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.

>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.

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.

[rickman]

On 5/8/2017 8:19 PM, mike wrote:
>
> 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.

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.

--

Rick C

[mike]

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.

[mike]

On 5/8/2017 7:05 PM, Jeff Liebermann wrote:

>
>> It'll cost you $200, but if your time is worth anything, it will
>> quickly pay for itself.
>
> I have my finger on the buy it now button. Someone help me to resist
> the temptation.

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.

[gregz]

<olds...@tubes.com> wrote:
> 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.
>

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

[whit3rd]

On Monday, May 8, 2017 at 5:21:14 PM UTC-7, mike wrote:
> On 5/8/2017 10:24 AM, bruce2...@gmail.com wrote:
> > On 5/8/2017 11:36 AM, ohg...@gmail.com wrote in sci.electronics.repair:

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

> 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.

There is a valid use for blackstrap molasses!
... I'm sure the foot powder tastes better on pancakes, though.

[MJC]

In article <cd72hcdoq7eptg838...@4ax.com>,
je...@cruzio.com says...

>
> On Mon, 8 May 2017 11:46:44 -0400, rickman <gnu...@gmail.com> wrote:
>
> >I can put mine up to my ear canal and read 96 °F.
>
> Are you sure that it's not reading the temperature of whatever is near
> the other ear?
>
> (Sorry, I couldn't resist).

I believe you can keep the fluff out of the line of sight using mental
floss!

There was a quote from the Goon Show that Eccles (IIRC) didn't have a
light in his eyes - it was the sun shining through the back of his
head...

Mike.

[ohg...@gmail.com]

On Monday, May 8, 2017 at 8:21:14 PM UTC-4, mike wrote:

>
> 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.

I've seen a lot of those little smd film caps short recently on TV mains and tcons. I don't have an imager, but I give the circuit board a dose of freeze spray, feed in a limited current to the shorted line, and see where the white frost blanket thaws first. With any luck, it's the actual component that thaws first. Problems arise when the offending shorted is close to zero ohms and some feeding component gets hot.

[mike]

That's why it took me so long to find that one.
It was absolutely, positively zero ohms. It shut down the power supply
instantly.
I had to tap into the correct branch of the power distribution and
apply current there to generate any heat.