Bob Higgins wrote.
"Type B thermocouples are expensive; even for fine wire, short, uninsulated
couples, because they are made from platinum. They may be 10x more
expensive than type-K and extension wires are just as expensive.
Additionally the signal level is smaller with type-B which means more
noise in the measurement."
Type S is Platinum/Rhodium and has a higher output than type B that uses
platinum/with some Rhodium on the platinum side. This is more stable
for really extended times at high temperature as it reduces Platinum
diffusion to the Rhodium leg. It does have a lower output than type S.
We also found that the wire diameter needs to be >15 thou diameter as
the platinum forms crystals nearly that big, in say a year, that causes
failure.
