Message Board Thread - "Camera settings?"

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Camera settings? Pete 12/16/2005
I have a couple of questions for thermographers:

Do you change your default settings?

Do you care about quantative data?

Were you handed the camera, sent to Level I, and expected to be an expert when you got back?

The reason I am asking these questions is that there have been several images posted on these message boards that have been taken with the camera's default settings.

If the settings don't matter why is so much time spent teaching us about them and the effects settings can have on data?

For example: It concerns me to see am image taken outside in a switchyard appx. 30-40' with the default settings of dist=6', Tref=20 c, Tatm=20 c, and none of the more experienced thermographers speak up about the effect wind & distance can have on the data.

Maybe it is just the industry I am in but, if I went to management with an image taken with default settings I would have no credibility. we make our decisions based on actual delta T or rise on a trend.

Sorry to get on my soap box but, a thermographer always needs to push their learning curve and think about the "What effect"

What effect does:
emissivity play on my data?
reflection play on my data?
pressure, flow, level, current play on my data?
external influnces Play on my data?

I am not saying that the settings need to be set for every single image we obtain but, I do think we need to be in the ball park. Otherwise it is garbage in = garbage out.

Thanks for listening



 
Re:Camera settings? jdemonte 1/3/2006
"What effect does:
emissivity play on my data?
reflection play on my data?
pressure, flow, level, current play on my data?
external influnces Play on my data?

I am not saying that the settings need to be set for every single image we obtain but, I do think we need to be in the ball park. Otherwise it is garbage in = garbage out."

Pete,

Your question is a good one. A higher emissivity target will generally give you much better data since most of the radiation coming from the actual target surface is based on it's own temperature and NOT the reflected apparent temperature. What this means is that even an untrained thermographer who constantly gets qualitative data will be close to the real temps most of the time.

Does that mean that the untrained thermographers are in the ballpark when it comes to environmental influences? Sure, since the environment actually affects the real temps. The problem with that is when the untrained individual ONLY refers to a severity criteria of some sort and BELIEVES that the problem is of a less critical nature because they didn't understand the cooling nature of forced convection or the radiation heating from the sun resulting in lower contrast and temperature differences.

It is the mediocre emissivity (.5-.8) or low emissivity (<.5) that will prove costly when a thermographer leaves the emissivity and treflected (background or Tamb on some cameras) at camera default.

How much will atmospheric temp, humidity, and distance settings in the camera affect quantitative data? From the 30-40' that you mentioned, not much. To see a Distance setting stuck at 6' is usually not an issue for most images.

There are NO settings in infrared cameras that can accurately compensate for the effects of wind/forced convection, rain, steam plumes, etc.

An infrared thermographer should know all of those points stated above and more. You don't ALWAYS need quantitative data from the IR camera to do the job correctly as long as you have other technologies to find the root cause and define the severity. However, I have run into situations where a proper Treflected was absolutely necessary prior to adjusting emissivity...

Hope this helps a little, Pete. If you would need any more details, please feel free to e-mail me at joe.demonte@flir.com


Thank you,

Joe DeMonte
ITC Instructor
 


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