Electronics > Metrology

DIY Low EMF cable and connectors

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martinr33:
I have some bare copper banana sockets on a 0Ohm resistance standard.

I liberally dosed them up with Deoxit Red, screwed them loosely together and put the vinyl caps back on.

Some months later, there was a tinge of green in the Deoxit and the terminals looked fine. However, that's after a very long time and with a liquid layer. Seems that Deoxit is partly oleic acid. But I would exect that acid to very quickly denature when used as instructed.

The flip side is that Deoxit is pretty hopeless at treating corroded copper spades. For that, I use vinegar immersion and a fresh water rinse.

I was skeptical of Deoxit for a long time. However, I have found it very effective in improving contact performance in batteries and potentiometers. And HP recommends it for use with the 3458A.

Overall, you should have a small bottle around.

leighcorrigall:

--- Quote from: martinr33 on February 12, 2022, 01:24:24 am ---For that, I use vinegar immersion and a fresh water rinse.

--- End quote ---

Acetic acid (essentially synthesized vinegar) is very effective at removing copper oxides. This is what is commonly used in metallurgy. Wear gloves and use a fume hood well-ventilated area when using the high-molar concentrate because it will burn you and is bad for the lungs. Acetic acid stinks. To prevent tarnishing, rinse with water immediately followed by drying with a clean cloth (or compressed air when the geometry is complex). C101 will remain oxide-free for months after treatment. If the part oxidizes in a few days or weeks, you may have either contaminated it or you are working with a lower purity copper (e.g., C110 and C122).

If all you can access is grocery store vinegar, heat the acid to improve its activity. An ultrasonic cleaner will also help encourage oxide stripping.

 ;)

martinr33:
Here's a picture of the business end of the latest Fluke metrology cables for the 8558 multimeter.

 - the cable is 22GA PTFE shielded twisted pair. It is black, not white.
 - the ends are sleeved in silicone rubber. They are very flexible, so much so that the PTFE insulation may have been stripped back inside the sleeving. They do not behave as if they are still insulated with PTFE, as they will not hold a bend. I wonder if the insulation might have been removed and the wire untwisted to make it more flexible.





TimFox:

--- Quote from: OscarM on February 10, 2022, 07:41:43 pm ---Apologies in advance if this has been covered somewhere but I have looked and failed to find it.
Is there any merit in connectors like this?
[attach=1]
Available as FMTC-CU-M for about $5
It is meant for 'copper thermocouples' which strikes me as odd but might be suitable for this application.
Presumably Deoxit is a good idea.
Mates in chassis mounting or inline are available.
PCB mounting is also available.
I have also seen a version with round pins which is larger.

Clearly it isn't shielded/guarded but on the other hand it is small so the coupling loop for EMI is small and the pins are in close proximity and so will be close in temperature (which shouldn't matter because it is all copper)

--- End quote ---

Those thermocouple-style connections are designed to connect copper wires used after a ice-point calibrator (real ice or electronic circuit) that connects the thermocouple materials into the world of copper connections.  Mechanically, they are the same as the connectors for J, K, etc. thermocouples that use the same alloys as the wires.

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