BNC-Thermocouple Adapter

[ddrop]

Hello everyone,

I'm trying to attach thermocouples to my USB 6259. Does anyone know of a thermocouple to BNC adapter or something of that sort? What I need is to attach my thermocouples to one of the analog inputs (which are all BNC female). If you find any links to products, please feel free to post them...

Thanks so much!

[ddrop]

Also, just a thermocouple that has a BNC adapter on the other end would work...

[Jake_G]

Hey ddrop,

You should be able to connect your thermocouple to one of the BNC connectors. The inner part of the BNC connector is the positive terminal and the outer shell is the negative terminal. The only downside is that you would have to do CJC (Cold Junction Compensation) manually.  To do that, you would enable the CJC and read in from AI0 in your program and do the compensation from the reading on the thermocouple on the BNC in your program as well.

[ddrop]

Hey Jake,

I just did this but it seems like I'm actually getting more inaccurate responses. It's weird... when at a normal temp (22C) the signal I get through my filter is fairly flat, but when I apply a temperature it gets VERY noisy. (By the way, I had been using a banana plug to attach my wires to the BNC before, and it generally had the same amount of noisiness on all ranges of temperature).

[Jake_G]

Hey ddrop,

There shouldn't be any problem fabricating TC to BNC connections as long as you provide good shielding for those cables. Since thermocouples typically are low voltage signals picking up a little extra noise is somewhat expected.  To eliminate this effect, try to keep your system away from electromagnetic interference sources that could couple into your cables.

Sometimes noise is actually introduced by the measurement devices themselves. Therefore, I would suggest you to try measuring a known voltage such as a battery. If the signal is still noisy, then your measuring device might be introducing the noise. For reducing noise on BNC connections, there is a good knowledgebase article that explains what you can do.  It is located here.