Low Thermal EMF BNC connection options

[zigggggy]

Hi all. I am trying to measure the EMF voltage of an acquisition system with BNC inputs (DUT). The EMF voltage that I am measuring is in the single digit uV range and I am finding it very difficult to make this measurement consistently with my current setup. After doing some research, it is clear that my setup needs some upgrading so that all the connections between the DMM and the DUT are copper. Much of what I have now is nickel plated.

I am currently demoing the Agilent 34420A DMM (a nanovolt meter) and it comes with a low thermal emf cable with spade copper lugs. The issue I am having is finding a low thermal EMF adapter or cable with a male BNC connector on one end and spade copper lugs on the other. I figure that if I can find such a cable or adapter, I could connect both the DMM and DUT together using Pomona 3770 gold plated Tellurium Copper posts.

Has anyone seen such a cable or maybe can offer suggestions on how to make one? Is there maybe an easier solution? Thanks!

[ap]

There are BNC cable that use pure coper wires internally. Just strip it and then ensure direct and good contact between the two wires and the spades. Even if the BNC cable e.g. consists of silver plated wires (the better cables have that) you can use them and will hardly detect a difference.

[cellularmitosis]

The issue I am having is finding a low thermal EMF adapter or cable with a male BNC connector on one end and spade copper lugs on the other.

There are a few of us on this quest...

https://www.eevblog.com/forum/testgear/lking-for-gold-plated-tellurium-copper-banana-plugs/

https://www.eevblog.com/forum/metrology/diy-low-emf-cable-and-connectors/

https://www.eevblog.com/forum/metrology/low-thermal-emf-binding-posts-a-quality-warning/

As soon as I get my (broken) HP 419A up and running, I can potentially start making some meaningful measurements (or at least comparisons).

[martinr33]

I've picked up some Viborg banana speaker plugs on eBay. They have them in pure copper, and palladium plated. These are copper, not brass (most commonly described as "copper") or pot metal!

They run about $5 each - and you can also get them from Amazon. I'm busy building some cables with RG58 coax.

[zigggggy]

What if I decided to make my own cable using a 20 AWG Belden RG58/U and crimping a male BNC connector on one end and banana plugs on the other end? I would connect the center conduct of the coax to one banana plug (using screws) for the high side and I guess I would connect the other banana to the shield for the low side? I am not sure how well this would work because the shield is obviously not copper, but I don't know how else to go to a BNC connector??

[branadic]

They are also available with gold plating:

https://www.amazon.de/Viborg-Audio%C2%AE-Lautsprecher-Steckverbinder-VERGOLDET/dp/B01N00ZH80/ref=sr_1_62?srs=9924491031&ie=UTF8&qid=1504730184&sr=8-62

Not sure how they really perform. Any experience?

-branadic-

[martinr33]

Mine are working well. Good find on the gold. They did not have those when I bought palladium, and they did not have palladium when I bought copper.

These are definitely solid copper - I ground the back end to make sure they were not plated. The screws are brass, but they are shorted by the copper.

I can reverse the leads and get the same readings on my 8.5 digit boxes with a 10V supply. There's still a little bit of thermal, but it settles fast.