spectral emissivity

[samot61]

Hi
Where can I get the spectral emissivity of materials like water, glass,asphalt, etc?
Thanks

 

[IRstuff]

There are websites:

http://www.electro-optical.com/bb_rad/emissivity/matlemisivty.htm

which can be found through websearching.

TTFN

FAQ731-376

 

[samot61]

Thanks, for your quick answer.
My question is referred with emissivity vs wavelenght for the 3 to 5 and 8 to 14 micrometers atmospheric windows

 

[IRJohn]

Please be aware that emissivity tables are often inaccurate, due especially to variations in waveband, material temperature and an inexact description of surface condition (what does "oxidized" really mean?!). All to often the source of the data is also not adequately referenced. Do a web search and compare the results and this is obvious.

The most important thing to remember, however, is that radiometric measurements made under field (rather than lab) conditons are typically HIGHLY inaccurate when the emissivity correction is below approximately 0.6, i.e. all metals that are not coated or extremely oxidized. Unfortunately camera manufactures are not forthcoming with this fact.

If you need to convince yourself of what I am suggesting, take any coins you have in your pocket, put them in pan and heat them to approximately 100C. Try to measure their temperature from several different vantage points using the emissivity correction values you've found in the tables. It is hopeless.

Another great site for information about this topic is:

http://www.temperatures.com

If I can be of further assistance, please feel free to contact me.

If I can be of further assistance, please feel free to contact me.
John Snell
Snell Infrared

http://www.snellinfrared.com

 

[Lucitano]

I completely agree with John Snell. The emissivity tables that you can find in hundreds of places, sometimes even in the internal memory of the infrared camaras, are not reliable. If you need accuracy you better measure the temperature with a contact thermometer and adjust the emissivity in the camara to reflect the same temperature.

So far is the best methot I personally know to meter temperature in metals and some polished surfaces.

A nice place (in Spanish) to get information is:

http://www.amperis.com/productos/camaras-termograficas/

I hope it helps,

Lucitano