Group buy - low thermal EMF LEMO connector for nanovoltmeter (34420/2182)

[HighVoltage]

With the new original short, I calibrated the 34420A to 0 OHM and the value shown on the 34420A stays very stable between 0.000,000,0 and 0.000,000,1 even for days and with temperature changes.

When I install my self made LEMO short and let the instrument settle for a few minutes, the value shown is always between 15.9 around 18.6 uOhm, depending on temperature in the lab.

So, the pure copper original connector makes a difference.
But this difference is larger than I had expected.

 

[CalMachine]

With the new original short, I calibrated the 34420A to 0 OHM and the value shown on the 34420A stays very stable between 0.000,000,0 and 0.000,000,1 even for days and with temperature changes.

When I install my self made LEMO short and let the instrument settle for a few minutes, the value shown is always between 15.9 around 18.6 uOhm, depending on temperature in the lab.

So, the pure copper original connector makes a difference.
But this difference is larger than I had expected.

That could potentially be coming from your shorting connection on your DIY plug

[HighVoltage]

That could potentially be coming from your shorting connection on your DIY plug

Agree...
Although I use a pure copper rod, squeezed it between the 4 solder studs and made sure I had a good mechanical connection to all 4 gold plated studs. Then added solder.
I should try a different configuration.

Here is a picture of my gold plated LEMO connector with copper rod soldered to all 4 studs.
 

[dietert1]

Instead of trying to simulate a 4W ohms measurement of a short, you could try to make two independent shorts for drive and sense, maybe with a 1 KOhm resistor between the two shorts. In order to keep the drive current separate. And the original has that plastic sleeve around the "thermal head".

Regards, Dieter

[martinr33]

If the pins are gold plated, then they are brass not copper. I have both brass and copper pin shorts, so I will have to try measuring both. Maybe you could also check for the voltage measured across the short?

I ran a quick test on a 34420a that I have had running for a couple of weeks using shorts that I made. The Lemo short uses cadmium-tin alloy. These are built as a 4-way short.

Copper pin Lemo connector with nut:   -12nV   0.2nR
Brass pin Lemo clone push/pull             -7nV    0.3nR

I'd trust the Lemo copper pin as the better of the two, but the differences are very small.

The clone shorts are very convenient because of the push/pull connection.