We presently have the Fluke 4181 for 35 to 500 degrees C. Other than the 4180-156 are there any other manufacturers making an IR Black body that goes below 0 C ?
You might want to look at Electronic Development Labs (www.edl-inc.com) we have two of their Ultra temp baths and their high temp blackbody source. They are a smaller company and have provided us great customer service.
I do not see a ton of these but I have not seen any that need below 0 degrees C. Is there much need for that?
We have customers that want the full range calibrated. Not sure they use it below 0 deg C. So I'm trying to figure out if I could put a target in the temp chamber and cool it down to -25 and monitor the target with a PRT or buy a different IR source.
Take a look at Santa Barbara Infrared, they might have what you need. http://www.sbir.com/