Message Board Thread - "Emissivity problem"

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Emissivity problem Dominic 8/8/2007
Hi guys,
I have a little problem to get a temp. on 2 similar materials.
Is this possible that I am incapable to have the temperature of a material? I used the technique of electric tape and all has well worked on the other materials except two. Hereis one of the two IR images and real pictures.
 
Re:Emissivity problem Dominic 8/8/2007
Here the real picture.
 
Re:Emissivity problem IRJay 8/9/2007
What type of tape are you using? Using a less than high quality electrical tape will produce erroneous results. The cheap tape is partially transmissive which produces some inaccurate measurements.
 
Re:Emissivity problem Gary Orlove 8/9/2007
This is a very shiny low emissivity surface that is difficult to measure without extreme care. I have analyzed your image with the following results:

T reflected = 31.7 C from the cold area to the right of the tape. There was no other data to pull this from.

Tape temperature = 60 C using e=.95 and Tref= 31.7C

Emissivity of the spot 2 area calculated at 0.042 based on an assumed temperature of 60 C and Tref = 31.7 C

Gary Orlove
Infrared Training Center
 
Re:Emissivity problem Dominic 8/10/2007
Hi Gary, Thanks for the answer. If I understand correctly what you are saying is that it is almost impossible to get a GOOD reading due to the fact of the I reflexion of the metal. There is the same mechanical equipment behind me that creates more heat.
Are you telling me that the emissivity is around 0.042 for this material? This is really low isn't?

The possibility for me is to put a "screen" behind and each side of me to reduce de reflexion of all the things around.

IRJay-} I'll have a look on the type of tape to make sure it's a good quality.

Thanks again guys for all the info.
Dominic
 
Re:Emissivity problem Bob Berry 8/11/2007
Dominic wrote:
, Thanks for the answer. If I understand correctly what you are saying is that it is almost impossible to get a GOOD reading due to the fact of the I reflexion of the metal. There is the same mechanical equipment behind me that creates more heat.
Are you telling me that the emissivity is around 0.042 for this material? This is really low isn't?

The possibility for me is to put a "screen" behind and each side of me to reduce de reflexion of all the things around.

IRJay-} I'll have a look on the type of tape to make sure it's a good quality.

Thanks again guys for all the info.
Dominic
Screening the area around you will NOT help.

This is a highly reflective surface, it will reflect the screen, if you put up a screen. The only way to get a measurement on this is to change the surface emissivity. Even seeing a problem on a surface with an emissivity this low may not be possible.
 
Re:Emissivity problem Gary Orlove 8/11/2007
0.042 is EXTREMELY low. It means that the material reflects 96 % of any IR radiation impinging upon it from the environment, almost a perfect mirror. It also means that it will emit only 4% of the radiation that a blackbody at the same temperature would emit, hardly an efficient radiator. Since IR cameras depend on material emission in order to illustrate thermal patterns and measure temperatures, with only a 4% signal and 96% artifact, this material is not a great candidate for IR inspection.

How about wrapping some paper on the surface to improve emissivity and view the thermal patterns?

Gary Orlove
Infrared Training Center
 
Re:Emissivity problem Dominic 8/13/2007
Wow thank you for all the answer. I'm happy to read all your comments because I thought I did something wrong when I get my temperatures.

The thing is, I never had to get a temperature from a material like this (High emissivity) so that is why I'm asking here if I did something wrong.
Look at the other part, just for comparaison that has paint on it.

Everything is clear now.
Thank you Bob for the comment too.

Have a nice day.
Dominic

 
Re:Emissivity problem Dominic 8/13/2007
Real image
 


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