thermocouple wire 2

[Datech]

I need a 50 foot thermococple wire ANSI type J Iron/ Constantan.The book says the total resistance of the two leads shall be 2 ohms for correct temp indication. How would I determine the wire diameter?

 

[StoneCold]

I've done a bunch of these and I never measured the wire diameter. Just specify that you need thermouple wire for a type J thermocouple and there you go. There are different grades of quality. Some are hard and brittle single strands and some are multistrand. I personally like multistrand but any of them will work. If the reading that you get is off a little bit adjust the zero in the controller or display to make it correct.

 

[imok2]

http://www.marshbellofram.com/tcp/TC_SelectionGuide.htm#SGTT

8 gauge for 50 feet = about 1 ohm and 11 gauge = about 2.1 ohms check out this web site

 

[Datech]

Thanks Stone cold and imok2. this will be used for cyl head temp. Omega as well as others sell the wire in different guages.I wasnt sure which dia. would work. imok the site you gave will be helpful. Thanks again

 

[danw2]

Can I ask which "book" advised having the T/C circuit be 2 ohms? What kind of indicator/controller nowadays cares?

Dan

 

[Datech]

yes Dan its a maintnance manual for a vintage aircraft.Indicator is an AN 5536-2

 

[danw2]

Ah-ha. That explains it. My Dad's 1940's, 50's & 60's instrumentation manuals cover this sort of topic, but nowadays it's quite rare to see input resistance as an issue. Thanks, Dan