Message Board Thread - "T Reflected and T Ambient"

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T Reflected and T Ambient Dave 1/9/2004
These terms are tossed around constantly and I'm now doubting myself... T ambient I take to be the room or surrounding air temperature and T reflected is the amount of infrared radiation reflected to the camera lens from heat producing objects in the viewing area. If you take a piece of dull cardboard and glue aluminum foil on one side, you should be able to read T ambient from the cardboard side and T reflected from the foil side. Both measurments being taken with emissivity set at 1. Is this correct or have I confused the issue? Thanks, Dave
 
T Reflected and T Ambient jgagnon 1/12/2004
Your confusion is understandable and is a result of the misuse of the term "Ambient" in some of our older cameras and software products. If you are using the Thermacam Reporter or Thermacam Researcher software there is a field called “Ambient temperature” in the “Object Parameters” section. This refers to the reflected temperature that you would measure from the aluminum foil with the emissivity set to 1. There is also a field in the software called “Atmospheric temperature”. This is the temperature of the air surrounding the object you are measuring. With the newer cameras, such as the FLIR E4 and P60, the reflected temperature is correctly called “T reflected” in the camera. Older FLIR and Agema cameras such as the PM-695 and the 570 called this reflected temperature value “Tamb”. So, in relation to the FLIR cameras and software products, “T ambient” and “T reflected” refer to the same thing. I apologize for the confusion, our cameras and software products are gradually being changed to correct this problem. If you have any additional questions please let me know.

Jason Gagnon
FLIR Systems Technical Support
jason.gagnon@flir.com
 
re:T Reflected and T Ambient Gary Orlove 1/12/2004
You are right; this can be a confusing subject. There is no standard in the industry for these terms, so different camera manufacturers each can call them something different, and some don’t even allow a user to set the reflected parameter, you have to take what the camera thinks it is, right or wrong!

But you are essentially correct in that T ambient is the temperature of the surrounding air (sometimes called T atmosphere) and T reflected is the amount of infrared radiation that can be reflected to the camera from the surface of your target (the actual amount depends on the reflectivity of your target; for opaque materials this is 1 – emissivity).

“If you take a piece of dull cardboard and glue aluminum foil on one side, you should be able to read T ambient from the cardboard side and T reflected from the foil side. Both measurements being taken with emissivity set at 1.”

You are partially correct here. You set the emissivity to 1 to measure the reflected radiation from the foil side, but to be accurate on the cardboard side you have to set the emissivity of the cardboard (~0.92) and enter the T reflected parameter as well.
Hope this clears it up for you.

Gary Orlove
Infrared Training Center
 


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