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Measuring water temp with infrared and some other questions

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pak

pak

Member
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Joined
Mar 21, 2005
Location
Tracy, ca
I got one of those infrered laser temp guns. I was wondering if this was an accurate way of measuring the water temp in my loop. The reason I ask, is because I want to see how close to ambient my water temp. Ideally, ambient is best correct? Or can you go a little lower. Is reaching ambient even possible with a conventional radiator and fans?

--pak
 
We know water boils at exactly 100 and turns to ice at exactly 0 (Must use pure water must be near sea level etc etc). Eg add impurities to water and it will only freeze at - 10 instead of at 0. If you live in the mountains water can boil in your hands. Another quick calibration point is the human body which is usually at about 37 degrees but can vary slightly between individuals.

I know my thermometer reads 0 in ice and 100 in boiling water so it's accurate (this is how we calibrate stuff in the lab). Probably a good way to test the accuracy of the infrared temp gun is to point it at a block of ice and then point it at some boiling water.

Yes you can get ambient temp = water temp (depends on your setup)
No you cant get ambient temp < water temp (unless TEC is used)

From my experience the water is nearly always = ambient temp. But then I have a monster water cooling setup.


 
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I am sorry. I should have stated my question more clearly. I know my gun is accurate, but is pointing the laser at the tubing accurate? I think the asnwer to my question is there are too many varibles now that I think about it more.

--pak
 
I have never used a gun to measure temps...

Pointing the gun at a tube probably measure the temp of the tube, not really the temp of the water.
 
pak said:
I am sorry. I should have stated my question more clearly. I know my gun is accurate, but is pointing the laser at the tubing accurate? I think the asnwer to my question is there are too many varibles now that I think about it more.

--pak
Click to expand...
What brand, model do you have? Is it 8:1, 30:1, 50:1?
 
IIRC the color of the material will affect the reading of the IR reader...

At least that's what the tech told me in our lab when it was calibrating it...
 
That is a 12:1 distance to spot meter which means that it shoots a one inch circle at a distance of twelve inches. That looks to be a re-branded Raytek. Just keep in mind that the air inbetween the two points does effect the outcome so put it up against the tube. Also the refectivity of the surface (emisisivity) will also effect the reading. Shiny is not good.
 
Take a temp probe, stick it to the top of your radiator (top, not side), and voila, insta water temp probe. Cover it with a piece of double stick tape and put some foam over it. I've been doing that for about 2 years now and it works great.

I wish heatercores could fit inside my case. My water is ~5-7 above ambient with BIP GTS 120+240 and 3 yate loons. With external box with 2 double heatercores and a single 120mm it was always ~1-2 above ambient.
 
How accurate do you think that is? I just happen to got a fan controller today that has two of those temp things on it.

--pak
 
That gun is like 300 bucks you must be keen to measure some temps!

How do people calibrate that gun to make sure its telling the truth?

Before I shoved a thermometer into my res I also used to put a thermal probe on the rad but this wasn't as accurate and somtimes the readings were a bit off.
 
I have the gun for work use and used it a lot for RC cars. So the $300 has been well spent and used. I would like to have something as accurate as your thermo set up, but with out the big res.

--pak
 
pak said:
If this method is accurate, I am ~1c above ambient.

--pak
Click to expand...

Actually, if you dont' have any TIM in between your probe and rad, you're probably .5 or less above temp. :beer:

Could use some ceramique. If you want something even more reliable use 2 part thermal epoxy and set it permanently on there. But I find that simply placing the probe on the rad and taping/covering with foam insulation a quite precise method of measuring water temp, not to mention inexpensive.
 
One problem you may run into is that water absorbs infrared light and transforms it into heat rather quickly. Red and Infrared light (Red having the longest wavelength of visible light and IR being ~3 times longer, I believe they are completely absorbed within a few feet) are absorbed moreso than blue light (shortest wavelength of light) and other colors. This is why a lake or the ocean appears blue and also part of why the sky has a blue tint (light refraction being the main reason iirc). For this reason i don't think you'll get a good reading unless you keep the travel time of the beam of ir through the water very small.

Also temp sensors can be rated from +/- 3° to +/-15°. You need to be sure to calibrate the thermistor (or test it against a real mercury or alcohol thermometer) before you deem it accurate.
 
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Maviryk said:
Actually, if you dont' have any TIM in between your probe and rad, you're probably .5 or less above temp. :beer:

Could use some ceramique. If you want something even more reliable use 2 part thermal epoxy and set it permanently on there. But I find that simply placing the probe on the rad and taping/covering with foam insulation a quite precise method of measuring water temp, not to mention inexpensive.
Click to expand...

I happen to have all of that. I don't want to use the permanent method though. Ill see if it changes temps at all.

--pak
 
Thermochromism....

You can buy temperature sensitive dyes that change colour as the water heats up!

So at room temperature the water is a cool blue colour but as the water heats up it turns into hot red, this would look quite neat and would be nice indication that things are getting too hot.

You could see the colour change as the water moves in the loop! Hot water goin into the rad is red cool water leavin the rad is blue!

All the water cooling additives should incorporate these kinda dyes insead of the yuck green colour...
 
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Well my goal is not to alarm me, it is more to tell me the current temp to get as closest to ambient as possible.

Thermaltake makes these. Sensor

Looks decent. I would question how much it restricts flow.


And an update on the temp on radiator idea. I scratched off a little bit of the paint and put some Thermalright ceramique on there directly on the copper. Right now, I am ~1.5c above ambient and have seen it as high as ~3c above ambient fully loaded.

--pak
 
Personally, I'd just paint a thin spot on my radiator end-tank flat black and read off of that, and call it a day.
Lab grade accuracy is an animal you'll chase a long time without success.

I use an Aerogate II to measure my temps using a thermocouple probe taped to my copper manifold on a dot of TIM...also not lab-accurate, but better than the "finger in the res" method. ;)
 
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