The 121 manual specifies operation temperature 0 - 50C, so -10C is outside this range. But the NTC sensor conversion routine seems to be limited to -25C to 85C so at least I hope it is reasonable accurate between 0 - 50C.
Wow, 0 C as a minimum operating temperature? That is extremely poor. I used to live in Canada, a meter that doesn't work below 0 C is garbage there, useless for anything but exclusively indoor work.
I looked up a Fluke 87 and they claim -20C as their minimum. That is reasonable, a lot of things start acting up at -20. But 0?
?
I would imagine that most functions on the 121 work fine well below 0C, perhaps that figure is primarily because of this specific thing. But still, wow, that is a very limiting specification.
Now I'm interested in seeing what functions of the meter don't work at -20.