No, all thermocouples are not the same, there are many different types,
J,K,T,R,S, and so one. The difference is the materials used for the
wires. There must be 2 dissimilar metals for the junction to produce a
voltage. Some use iron/constintan, others use copper/ cupronickel,
others use different metals. They have different outputs at the same
temperatures and are not interchangeable. Most Tc's for home use will
be either J or K, and of those most should be J. You can tell by the
wire insulation colors. J is red and white, K is red and yellow. Red
is negative. As long as your wire color on the old one matches the new
one it will be ok.