I want to undo a mistake I've posted a few times in posts dealing with building PID controllers and the meaning of the wire color on thermocouples. Recently I have learned from three different projects that the tc's from China don't adhere to US/Canadian industry standards.
What's (sometimes) coming from China-
Red=positive
Blue=negative
This revelation, probably already well known by others, came from info from dikman, 3jimbo3, and bigarm.
That is bassackwards from ANSI standards-
http://www.omega.com/techref/colorcodes.html upper left corner
Fortunately nothing bad happens from connecting it backwards, the controller will show a stupid temp reading but that's all.
For those building a controller and including connectors to allow unplugging the TC from the enclosure, be aware the connectors chosen should be specifically made for type K tc's. The metal used for the contacts needs to be correct. Auberins is a great source.