Low emf cable assembly techniques

[HighVoltage]

When I started to build my own Low EMF cables, I tried many different crimp tools and it got better and better. I probably wasted lots of expensive LowThermal, Inc. terminals and lugs but at the end I got really good results from the looks of the crimping and stability and repeatability.

Here are some pictures of a few different cables and lugs I crimped.
The most expensive crimp tools are not always the best for the job.
Also shown is the connection of the shield to the ground cable.

[HighVoltage]

And a few more pictures

[mzzj]

I have always wondered, does adding extra solder cause any thermocouple effect at all? Or because there is some copper to copper contact, this doesn’t happen?

For thermal EMF you need temperature differential over dissimilar metals. In this case it any temperature differential over the joint is extremely small and the generated thermovoltage is shunted by direct copper-to-copper connection.
Effect is probably REALLY small and you would need nanovoltmeter to worry about it (and possibly even then need to introduce some unrealistic thermal gradients)

I just did some experiments with 3458A, 1mm2 "lamp cord" wire and 40/60 solder:

1. "lap solder joint" with wires overlapping each other by about 5mm(overlapping but not twisted together): max EMF about 0.3uV when I introduce large thermal gradient by grabbing one side of the copper wire between my fingers.
2.  "butt joint" with 1mm gap bridged with solder: 1.7uV max EMF  when I introduce large thermal gradient by grabbing one side of the copper wire between my fingers.
3.  "twisted lap joint"  max EMF about 0.3uV when I introduce large thermal gradient by grabbing one side of the copper wire between my fingers.
4.  "twisted lap joint" with tinned copper ferrule crimped over the joint: 0.03uV

All measured with NCPL=500, Math Null. Short-term stability seemed to be better than 0.01uV during measurements.
"Crimped and soldered" joint is probably better than number 1. or 0.3uV.
Also note that this was under rather extreme thermal gradient over the joint. 
 
At some point you would need to start to worry about copper vs copper vs copper, different batches having dissimilar thermal EMF or cold-working introduced stresses changing the thermal EMF.
(These are all very real problems with thermocouples)

[coppercone2]

the crimp tool die pressure curves has a inflection point around the region that is best mechanically and electrically. you can deviate from this region with pressure control to get a lower resistance /stabler? electrical connection at the expense of stressed copper, which will be mechanically weaker, or a mechanically stronger joint that is electrically weaker, if i recall. optimum pressure probobly depends on strand parameters also.

so you can adjust crimp pressure/height so long your requirements are met, but it would require large scale testing.