Are infrared visual thermometers good for measuring temperature on heat sinks?

JohnInTX

Joined Jun 26, 2012
3,940
Have you ever used infrared visual thermometers to check temperature on heat sinks for transistors?
I use one of those pistol grip IR thermometers with a laser LED for aiming and it works great for quick tests. For detailed thermal analysis, I use a thermocouple in a drilled heat well under the device itself. But you could get away with the IR gun for most things I would think. They’re pretty close.
 

JohnInTX

Joined Jun 26, 2012
3,940
There is no denying that the video is way cool and I can think of lots of ways that it’s better than an IR gun. It would show the heat flows, how well your convection cooling works etc. It would also be useful around the house to find insulation deficiencies. If you have the scratch go for it. Tools like that have a way of getting more useful over time as you work with it and figure out more uses for it. I use my IR gun after getting burned on a stepper motor and now use it to sweep the smoker to know when it’s evenly preheated. The video would be awesome for that. And most importantly.... TOYS!

But the cheaper IR gun is OK for general use too.
 

Vinnie90

Joined Jul 7, 2016
86
Just a quick heads up. Metals are refractive for IR...if you want to an accurate measure of the temperature it is best if you put a small piece of Kapton tape for example and measure the temperature of that ;)
 

Son Gạo

Joined Jun 23, 2019
6
Just a quick heads up. Metals are refractive for IR...if you want to an accurate measure of the temperature it is best if you put a small piece of Kapton tape for example and measure the temperature of that ;)
hi guy,

i really want to know " what is "Kapton tape "

i hope you will be posting PHOTO about it as well,
 

DickCappels

Joined Aug 21, 2008
6,086
At one company in which I worked the test engineers used a nice pyrometer to measure component temperatures. To get predictable emissivity they dusted the circuit with baby powder. The Kapton trick is a new one to me.
 

Vinnie90

Joined Jul 7, 2016
86
You want to use Kapton, or as @DickCappels suggests baby powder, becuase you want to have known emissivity to measure the temperature of the surface you are measuring. I use Kapton just because it's thin enough to reach the same temperature of the underneath surface and it's very resistant at high temperatures. But in principle you could use everything, even paint.
 

SamR

Joined Mar 19, 2019
1,622
I thought you were going to say use Kapton to hold a thermocouple with a dab of paste onto the heat sink which also works. Years ago when IR thermal scanners first came around, some yo-yo young engineers at the home corporate office convinced their superiors that it was imperative that they go to all of our plant locations and scan their electrical panels for hot spots (Electricians always work in pairs for safety). Talk about a free globe-trotting mini-vacation... And NO they did not find any at our locations and were probably using it to test the temperature of the beer in the bar at the beach after work.
 

Sensacell

Joined Jun 19, 2012
2,544
Google "IR Emissivity" to learn more.

This is essential to understand before trying to use an IR thermometer.
Most IR imagers have some settings to adjust for target emissivity, but it's much smarter to coat the target with a substance of known emissivity to eliminate the errors.

I just use some flat black spraypaint applied with a Q-tip
 

DickCappels

Joined Aug 21, 2008
6,086
During the 1970's kapton film was used to insulate and wrap wiring harnesses in fighter planes being built at that time. Sometime in the 1980's it was discovered that the kapton was breaking down with use, causing current leakage and thereby heating of the harnesses, causing crashes. While solutions were being researched, as a temporary precaution thermocouples were inserted into the harnesses and connected to a small computer with a speech synthesizer card to alert the pilot in the event of overheating being detected. The synthesizer would announce "This is your kapton speaking..."

Apolgies are offered.
 
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