Speaking solely about K type thermocouples.
I have noticed widely varying temperature ranges, but generally speaking around -50 C is the low end. I was looking into installing screw-in ones on some of my pieces. However, what I am seeing is that the screw-in types mostly show 0 C, as their low end.
Why do these screw-in types have a reduced range? Would it be preferable to use thermowells, with nipples?
The Sub-zero Thermocouple Measurement Problem
By “sub-zero” I mean any temperature measurement that is less 0 °C. It is generally not possible for thermocouple manufacturers to provide alloys that operate both above and below zero in the same thermocouple wire. And since the vast majority of thermocouple applications are for measurements above zero, that’s where the bulk of thermocouples are guaranteed to operate. Thermocouples for the substantially fewer sub-zero applications must be ordered specifically for that purpose.
I started a thread on a similar topic.