PWHT thermocouple attachment 1

[zibaeng]

Hi friends.
In separated junction method of attaching thermocouple wires (for PostWeld Heat Treatment), why do we attach (weld) each wire of thermocouple separately to the surface of the workpiece? Why not connected to each other? I know the wires of a thermocouple should be connected to each other and have electrical contact to produce a thermoelectric voltage.
According to AWS D10.10/D10.10M:1999, the wires should be in close proximity (6mm) to each other.
Thank you in advance.

 

[btrueblood]

If the ends are seperated physically, but connected electrically, they will measure the average of the temperatures at the ends. I think the purpose is to attempt to measure the bulk temperature of the part, rather than a single point.

 

[zibaeng]

Thank you, It seems to be my answer.