Best Dual Banana plug / shorting bar ( Handheld multimeter calibration ) ?

[Kiriakos GR]

At electrical tests and measurement sector there is no easy questions and neither easy answers.
This sector it is full of rabbit holes, your estimate of depth that you will climb down this is always unknown.

Soft cal (software calibration) for handheld multimeter this becomes known to me due my engagement with Agilent / Keysight U1272A.
First step at calibration procedure this is using a Banana plug / shorting bar, yes but which one?

When we fall at the first rabbit hole next ones are two, one goes to voltage range and the other to resistance range.
For the one heading to voltage range calibration adjustment the road is easy and simple, any shorting bar (dual banana) or pair of banana plug with sort cable will do the trick.
But the second rabbit hole this heading to resistance range calibration adjustment this is a very tricky road.

Generally speaking everything it would be easier if for example Keysight or HIOKI or others they would offer information of how many milliohms sorting plug they use in their own Calibration lab.
Personally I had to perform several experiments so to discover that HIOKI this using 0.60 Ohm as shorting bar.
Additional testing proven to me that Agilent / Keysight this using a bit higher than 0.60 Ohm as shorting bar.   

Practical benefit if resistance range calibration adjustment this performed correctly at Calibration accepted room temperature and with appropriate shorting bar, this is that you will need using lesser times the button for NULL / Delta Zero /REL.

After making my own shorting bar (this matching calibration of DT4282) by even trimming down my sorting bar diameter (originally a copper bar at 2.8mm) so to increase it resistance, then I tested it at three U1272A. 
This rabbit hole drive me further down by realizing that two or the three meters was measuring negative Ohm value (if there is such a thing ?) and at the level of minus 0.030 Ohm.
The third U1272A this was measuring minus 0.003 that is more close to DT4282 calibration.
In the next rabbit hole I did realize that all these minus and positive has to do with the room temperature of calibration and of the temperature of the shorting bar it self.
Then I did realize that my room temperature this is at 18C and about to drop even lower because of a cold day, and I did stop any further testing.
 
Rule No1, even with true copper banana in your hands and true copper wire at 2.8mm and everything soldered together at 500 Celsius, you have to wait for a warm day to finalize this item performance and name it as trusty Calibration accessory.

To be continued …… 

[Kiriakos GR]

Further research for ready product solutions shown that only one product this is close to the mark of 0,5 mOhm and this is SKS 4-19 L/1 from Multi-Contact.
I was had to compose one special picture this including detailed information since 2002 which this is missing from recent product catalogs.   

From the camp of Pomona their popular plug this is no other than MDP-S-0 according to datasheet this is less than 1,5 mOhm and no detailed information than that is offered.

From the camp of Hirschmann their similar product this has resistance of 8 mOhm, this is too high for calibration applications, but this seems more as regular item as jumper for audio equipment or generic use.


After such branded findings there is always and the Asian copycat market, all such product has be cloned and they are available at 1/3 of the price, for example I did discover clone of SKS 4-19 L/1  and I did send email at the factory in China so to ask if they can supply detailed specification of  resistance in mOhm?
They do mention beryllium copper and nickel platting.

And last candidate this is Pomona style dual banana plugs, the copycat version seems well made but it is not 100% successful clone, I would not trust this as Shorting plug, but for general use as component holder (electrolytic  capacitor / ceramic capacitor or resistance in the class of 1%) they seem as usable about testing such electrical parameters in the application of multimeter range calibration.