Bonjour a tous: Just found this post now, fascinating reading.
I think this iis a bit overwrought, and wonder any PCB at all? Why the 4 wire layout?
My experience leads to a simple plane of copper.
Also Both DCV (2 term) and resistance (4 term) should be checked.
Experiment: Using a new Keysight 34465A warm up 2 hrs , ACAL.
I have a variety of shorting plugs, some copper foil, gold plated foil and gold plated bananas, (eg from Gen Rad standard resistor).
With the gold bananas bare copper foil across all 4 connectors, OR 4 mm wide copper braid no plating,
About same with gold plated copper sheet or HP CAL shorting from 4195A. \\
DCV 200 nV
4 wire R ~500...800 uOhm
Good enough for me, the meter seems in CAL and in SPEC.
problem solved, NO fancy 4 wire PCB just a stupid sheet of copper foil and 4 holes.
Your thoughts and critique?
Bon Soiree,
Jon
PS: The fancy bananas seem to have a very tight fit into the 34465A input, hard to remove.