Many people ask us about how cold it can be and still have an imaging system do a good job. Even though we are nearing the end of winter, I wanted to address this as it has come up often in the past few weeks while I was at RESNET and other building-related conferences.
Two specifications are often given for an imaging system, operating temperature and measurement range. The first describes the temperatures in which the system can be reliably used, typically -15C (5F) or lower. I don't know exactly how this lower temperature is determined but I can tell you I've used systems rated like this at much lower temperatures. If I ever had a concern, I'd simply wrap the imager in some sort of insulating blanket. It has always continued to operate longer than I, the operator, could continue to operate!
The measurement range is defines the range of temperatures for which the radiometric calibration holds true. Temperatures can typically be measured outside this range, and usually quite accurately, the the manufacturer will not guarantee they meet the specified accuracy.
The bigger problem for any infrared system, especially the microbolometers that make up the vast majority of today's systems, is that they may not perform well at low temperatures because of reduced sensitivity. There is less radiation at lower temperatures. When I'm out at -30C (-22F) or lower (see attached), I don't have an expectation that the imagery will be as good looking as it is at freezing. If I'm looking at buildings, most will be somewhat warmer than air temperature but it can still be challenging to get an image that doesn't look noisy—it comes with the territory!
I hope this information helps folks as they are considering a cold weather system. My basic suggestion is that, with regard to cold weather operation, most of us have little to worry about most of the time even if all the images may not always be pretty.
Thermally Yours,
John
ASNT NDT Level III #48166
The Snell Group
www.thesnellgroup.com
www.thermalsolutions.org
800-636-9820