Richard Crowley wrote:

"Mike Rivers" wrote ...
My father (before I was born) worked as an electrician in a shipyard,
and wired up a bunch of pyrometers backwards because his boss insisted
that the red wire was positive and told him to wire them that way. The
other (the real positive) wire was white. Didn't matter (to the boss)
what the instruction sheet said. He knew better.

The wire colors of traditional thermocouples indicate which
type they are (J, K, etc.) and coincidentally also the "polarity".
They have never followed the electronics tradition of black=
negative, red=positive.

And just to confuse matters, K type thermocouples have just changed from
brown and blue conductors with a yellow plug to green and white conductors
with a green plug !

What is all that about ?

Graham