A little vigilance will save you a lot of time and aggravation when making thermocouple measurements.
A common mistakes people make when using thermocouples to acquire temperature data is to assume that the red wire is positive. I know what you’re thinking, “Isn’t it?” Nope. Contrary to popular belief (and what you may have seen in the movies), the red wire isn’t always positive. Thanks to the American National Standards Institute (ANSI), in the case of thermocouples, the red wire is actually negative (in the U.S. and Canada).