Message Board Thread - "Temperature Differences at Different Emissivities"

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Temperature Differences at Different Emissivities shockwave48 4/18/2005
Assuming everything else is constant (reflected & ambient temperature, distance, etc.), is the temperature difference (delta T) between two points the same at different emissivities? I'm asking because if I'm only interested in temperature differences between two objects, I'd like to know how important it is to have the correct emissivity. I know the actual temperatures can vary unproportionally.
 
Re:Temperature Differences at Different Emissivities Manuel 4/18/2005
think on this ..
if emisitivy does not correspond to material under observation, temperature reading will not be acurate.

regards
 
Re:Temperature Differences at Different Emissivities Gary Orlove 4/19/2005
Using the proper emissivities DOES matter!

Look at the images below. On the left we have a cold can with high emissivity tape and on the right we have a warm can with high emissivity tape. Note that the apparent temperature differences are much greater for the high emissivity surface compared to the low emissivity surface. Also note that the apparent temperature differential read on a spot tool also show this same difference.

To read correct temperature differentials you must use the proper emissivity.

Gary Orlove
Infrared Training Center
 
Re:Temperature Differences at Different Emissivities TDLIR 4/19/2005
I am assuming that Shockwave is asking if E makes a difference with Delta-T if everything else remains the same. I guess that includes NOT modifying the surface such as the example above with the Electrical Tape.

The answer is YES it still makes a difference. Look at the attached image of a breaker. The 2 images are of the same breaker and same spots and everything else is the same. Left image is at E 1.00 and right image is at E 0.60.

As you can see the Delta-T is affected by Emissivity!

Regards,

Sonny James
http://www.tdlir.homestead.com
 
Re:Temperature Differences at Different Emissivities shockwave48 4/27/2005
Thanks for the replies. Yes, I was assuming the same surfaces as well. This settles a disagreement I had with a Level II thermographer hired by our insurance company to perform infrared surveys on our electrical substations. He did not think that emissivity matters since he is only looking for "changes" (I also disagree with that), and doesn't even analyze the images after the survey. I'm only Level I, but I know his report is worthless!
 
Re:Temperature Differences at Different Emissivities gagusherhe 11/24/2008
shockwave48 wrote:
for the replies. Yes, I was assuming the same surfaces as well. This settles a disagreement I had with a Level II thermographer hired by our insurance company to perform infrared surveys on our electrical substations. He did not think that emissivity matters since he is only looking for "changes" (I also disagree with that), and doesn't even analyze the images after the survey. I'm only Level I, but I know his report is worthless!
ok this emissivity is afected by the electrical tape for this material the emissitivy is 0.98.
 


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