Multifunction DAQ

cancel
Showing results for 
Search instead for 
Did you mean: 

Do I need thermocouples with an isolated junction?

Solved!
Go to solution

I have an application where I need to measure the temperature of a surface at various points (approximately 20 to 30 points).

 

I'm using a cDAQ chassis with multiple NI9211 modules.

 

The surface to be measured is made of copper.  I'm concerned that there may be some spurious signals generated between channels if the thermocouples are not electrically isolated from the surface.

 

Do I need to use thermocouples with an insulated junction?

 

 

0 Kudos
Message 1 of 4
(3,591 Views)
Solution
Accepted by topic author egret2008

Hello egret2008,

 

You are absolutely correcct in thinking that you need some isolation.  Without it, you will get bad readings and interference between different thermocouples. To get your isolation, you will want to use a high-thermal, low-electrical connectivity material.  Vendors such as Omega sell both cements and greases with these properties.  Hope this helps and good luck in your application!

ColeR
Field Engineer
0 Kudos
Message 2 of 4
(3,565 Views)

There are also sheathed thermocouples that come in grounded and ungrounded versions. In the ungrounded case, the junction has no electrical connection to the sheath. Advantage is electrical isolation, disadvantage is a slower response time which may or may not be an issue in your application.

 

-AK2DM

~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~
0 Kudos
Message 3 of 4
(3,556 Views)
Thanks for the replys.  I will ensure the junction is insulated.
0 Kudos
Message 4 of 4
(3,536 Views)