Can someone please tell me what type thermocouple is used on standard home furnace control valves?
They are referred to as "30 MV Standard Thermocouple" and are used on home furnaces, water heaters, etc. of the standing pilot type. They usually have a 3/16" stainless alloy sheath about 3" long and are swaged in a copper tube about 1/8" diameter 18" to 120" long.
Robertshaw, Honeywell etc. make pilot type gas heating control valves. The specs imply they might be type K couples, but I don't know for sure.