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Temperature measurement in an inaccessible location [camera FLIR] ?
10-28-2016, 10:21 AM
Post: #1
Temperature measurement in an inaccessible location [camera FLIR] ?
Hi everyone,

This is my first message on this forum that i just discovered today, I hope it's the right spot to post. Smile
I hope I won't sound too dumb (i'm a beginner in infrared thermography) also english is not my native language.

So my problem. I have to realise a temperature measurement with no contact on a piece. I have at my disposal a FLIR camera ( http://www.flir.eu/science/display/?id=50093 ) that would be great for my tests.
Only problem : during the test it's impossible that the camera is perpendicular to the surface that I want to observe (which is important) due to the machine's congestion. Until a 20° angle it seems that it could be ok, but here it would be more like 45/50°.

So i'm looking for solutions, I don't know if there are some techniques to deflect (with mirrors?) the infrared radiation to get it to go on the camera? If it's simple to do or if it's more simple to use thermistors near the piece and calculate a field of temperature? Or others techniques to measure a field of temperature in an inaccessible location? I know there are some little carriageable camera, but they have to be used by hand and I can't be near the piece during the essay.

So here it is if someone know a technique to measure a field of temperature without contact or a trick to use a camera FLIR on those conditions. Sounds like using mirrors is a good idea, but I don't see anything on papers that I read, about using mirrors to measure with a FLIR temperature in an inaccessible location, so I wonder it's not that simple and multiply sources of uncertainties?


Thanks for reading me!
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10-28-2016, 01:22 PM
Post: #2
RE: Temperature measurement in an inaccessible location [camera FLIR] ?
Yes, mirrors is an option. Check Edmund optics, you are looking for a front surface mirror. You will need to measure the reflectivity of the mirror or with your camera and ResearchIR software you can do a user calibration with the mirrors in place as an alternative, this might be better.


Don't worry about English not being your first language, you probably put most people here to shame.
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11-02-2016, 04:05 AM
Post: #3
RE: Temperature measurement in an inaccessible location [camera FLIR] ?
Thanks, it's easier when you take time to write and use translation websites ^^"

I've checked Edmund optics, and from what I've understand, thoses mirrors are only for low temperatures? (Like < 200°C). I'll need to mesure temperature from ambiant to 500°C, so maybe a mirror to deflect the radiation won't do the trick?
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11-02-2016, 12:53 PM (This post was last modified: 11-02-2016 12:54 PM by Bobberry.)
Post: #4
RE: Temperature measurement in an inaccessible location [camera FLIR] ?
I'd imagine this means that the mirror itself needs to be below 200°C, but I see no issue with you measuring reflected temperatures above this.

You could also use a polished metal plate if this was a concern.
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11-02-2016, 06:24 PM (This post was last modified: 11-02-2016 06:27 PM by JKEngineer.)
Post: #5
RE: Temperature measurement in an inaccessible location [camera FLIR] ?
Without looking, I suspect that the T limit on the mirror refers to the ambient T for the mirror, not the reflection capability.
Also, I have had good results using a mirror finish aluminum plate as a reflector.
Jack Kleinfeld, P.E.
Kleinfeld Technical Services, Inc.

I see Bob Berry posted the same about the T limit. I loaded the page early this AM and then responded in the late PM, so did not see his.

Jack Kleinfeld, P.E.
Kleinfeld Technical Services, Inc.
1-718-884-6644
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11-03-2016, 06:33 AM
Post: #6
RE: Temperature measurement in an inaccessible location [camera FLIR] ?
Oh thanks that's a good news, I completely misunderstood the mirror's description!

As I was thinking it was not a solution I was wondering something else : could I do a "relative mesure" of the temperatures, using the camera from an angle?

To explain my thought : my "idea" is to observe only the differences of temperatures on the piece with the camera. And I'll mesure the temperatures with some pyrometers for exemples. After the essay, I will match the temperature measurement (obtain with pyrometers) and the images of the camera, so I'll have an image showing the temperature field of the piece. But I don't know if the image obtained with the camera from a 50/60° angle would be acceptable? (I can't try it on pieces as I don't have the camera or anything right now).


But I will check again mirrors too and maybe try both methods if I can.
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11-03-2016, 07:28 AM
Post: #7
RE: Temperature measurement in an inaccessible location [camera FLIR] ?
In order for your differences to be correct, each measurement would have to be correct, a error will not cancel out equally on two objects at different temperatures.

Emissivity varies with viewing angle, at 50-60 degrees of perpendicular the emissivity will not be the same.
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11-03-2016, 08:27 AM
Post: #8
RE: Temperature measurement in an inaccessible location [camera FLIR] ?
You mentioned comparing camera temperatures with pyrometer temperatures. Check the webinar with this link to see why they probably won't agree. http://www.flir.com/science/display/?id=55276
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11-03-2016, 10:04 AM
Post: #9
RE: Temperature measurement in an inaccessible location [camera FLIR] ?
Thanks for the webinar, it was instructive!

Mmh I think I may have poorly explain my thought here. I don't want to observe the differences between camera's temperatures and pyrometers's temperatures. I just want to mesure temperatures with pyrometers. But filming the essay with the camera too (from a 50/60° angle). And I will not take into account at all the measurement of the camera. But on the image of the camera I'll be able to see where my pyrometers are and I will say : "So there is my pyrometer n°1, the temperature of pyrometer 1 was XX°C, so this pixel of the image, which is of this color, is actually XX°C, etc..". And doing so, change the entire scale of the image of the camera. But i don't know if it's feasible.

I don't know if that was clear or if I just misunderstood your answer.
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11-06-2016, 09:42 AM (This post was last modified: 11-06-2016 09:43 AM by Bobberry.)
Post: #10
RE: Temperature measurement in an inaccessible location [camera FLIR] ?
If you set your camera up correctly, and enter all the parameters correctly, then I would expect the measurement with the camera to be better than the pyrometers. I don't see why you would need the pyrometers at all, and I would expect the setup suggested would lead to more questions than it will answer.
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