Thermocouple color code standards... - Page 1
Forum section: electronics / projects

author: PKTKS
author_rank: Super Contributor
timestamp: February 22, 2022, 02:29:49 pm
content: I am replacing a thermocouple with a more robust shielded (in figure) with metallic braid ...but... after some long searches about POS/NEG color codes I got more confused than when started...I would expect that RED would be positive while BLUE negative.. but no thermocouple color code sheet can agree even in the colors used and while Japanese JIS stands RED positive nobody else does that...This is a default made in china "K" thermocouple ... with BLUE/RED wiring..Which is positive? any clue welcomePaul

author: jpanhalt
author_rank: Super Contributor
timestamp: February 22, 2022, 02:43:59 pm
content: On my K thermocouples, the colors are red and yellow. Red is negative. It's also magnetic. The positive is non-magnetic.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 22, 2022, 02:45:33 pm
content: I remember some confusion about color codes, but it seems simple enough to heat it up and measure it with a DVM. The signal is small, but there should be enough to tell. The magnetic clue is also excellent.

author: PKTKS
author_rank: Super Contributor
timestamp: February 22, 2022, 02:46:17 pm
content: I am building a vote list...so far RED is winning the NEGATIVE position...Paul

author: PKTKS
author_rank: Super Contributor
timestamp: February 22, 2022, 02:47:34 pm
content: Quote from: Conrad Hoffman on February 22, 2022, 02:45:33 pmYep.. that hint of heating it up with a dmm attach should do the trick...I was so deeply buried in searching color codes that forgot about simple testing....Paul

author: TimFox
author_rank: Super Contributor
timestamp: February 22, 2022, 02:53:08 pm
content: I have a cheap digital thermocouple meter where it is easy to invert the thermocouple plug into the meter (bad tolerancing on the slots). I checked the TC by sticking it under my tongue, then called the coroner to establish the time of death since my body temperature had fallen to 55oF.

author: PKTKS
author_rank: Super Contributor
timestamp: February 22, 2022, 03:02:06 pm
content: Quote from: TimFox on February 22, 2022, 02:53:08 pmI even tried to invert them on the PID controller ... just to test the PID itself..Funny thing that the PIDshouldbe able to detect the inverted thermocouple..So far it worked both ways...go figure..Paul

author: jpanhalt
author_rank: Super Contributor
timestamp: February 22, 2022, 03:13:13 pm
content: It all depends on where you put "zero". Most commonly, it is at +273°K.

author: jonpaul
author_rank: Super Contributor
timestamp: February 22, 2022, 03:56:54 pm
content: Used them for decades, type K TC USANuniversal code is yellow pos red negmany other types of TC exist eg iron constantan, with different color code.Codes vary in other countries.https://reotemp.com/wp-content/uploads/2015/12/thermocouple-wire-color-codes.jpgJon

author: bill_c
author_rank: Regular Contributor
timestamp: February 23, 2022, 12:47:21 am
content: Another info source:https://www.omega.com/en-us/colorcodesThey may be a bit expensive, but they do have some good info.