Probe master leads and Be-Cu

[Miti]

Few days ago I saw some damaged multimeter leads in a box at work and I asked a technician if they have more. I ended up with a hard full of them, all the spring tip model. The banana plug and the silicone wire are very high quality on these probes. My first thought was to replace the cables on my kelvin probes that are really bad, then to make a 4 wire short with the banana plugs that I recover from the wires damaged at that end. I have a couple of questions though:

1. Do the wires in kelvin probes need to be shielded? The ones that came with the probes are, even though they are very low quality. I wouldn’t think it makes any difference.
2. Is it possible that the Probemaster banana plugs are made of Be-Cu? How do I know? The technical data sheet doesn’t say. I wouldn’t want to file and thread Be-Cu, even though I did it on two or them, the thought came after. 

Cheers,
Miti

[Gyro]

The Banana plugs and leads on those Kelvin sets are low cost Chinese too. The jacks may be Gold plated but I wouldn't rely on them being low thermal EMF, or Be-Cu.

Regarding Kelvin probe lead shielding. I don't think the ones in the photo are - shielding would need to be brought out to a separate shield connector. Shielding requirements depend on what sort of signal level and frequency they are passing. If they are used with DC, then a well filtered voltage input is all that is required. It might be different for an LCR bridge.


P.S. The best lantern style connectors have the lantern spring attached at one end, otherwise you end up with two contact points - lantern to socket and lantern to jack body.

[Miti]

Thanks, I was talking about Probemaster banana plugs being Be-Cu. I know that, ideally, a low thermal EMF 4wire short should be made of copper, since the 34401 and 3478 jacks are copper too, but I can’t find copper banana plugs.

[tooki]

P.S. The best lantern style connectors have the lantern spring attached at one end, otherwise you end up with two contact points - lantern to socket and lantern to jack body.

Example of such “best” ones? All the best lantern-style ones I am aware of — Stäubli, Hirschmann — do NOT have either end attached, just good and tight.

[Miti]

Example of such “best” ones? All the best lantern-style ones I am aware of — Stäubli, Hirschmann — do NOT have either end attached, just good and tight.

That's what Probe Master banana plugs are, good and tight and gold plated. That's why I thought they are good candidates.

[tooki]

Example of such “best” ones? All the best lantern-style ones I am aware of — Stäubli, Hirschmann — do NOT have either end attached, just good and tight.

That's what Probe Master banana plugs are, good and tight and gold plated. That's why I thought they are good candidates.

But the lantern on Probe Masters isn’t fixed, either. Tight, but not fixed.

[Gyro]

Example of such “best” ones? All the best lantern-style ones I am aware of — Stäubli, Hirschmann — do NOT have either end attached, just good and tight.

I was thinking of the original Multi Contact jack (the one which gave the company its name), where the 'lantern' is made up of individual captive sprung wires in a slightly diagonal pattern around the core (hence multi contact). I guess they're not lantern in the current stamped sheet collar sense but I'm not sure of an alternative name. I have a couple kicking around somewhere and will attach a photo if I can find one.


Edit: Ah, these look similar (but coarser and less diagonal)...

[tooki]

I think your memory might be slightly confused.

That’s not a lantern style plug. I don’t actually know what the generic English term for that style is, if we even have one. In German, those are called a “Büschelstecker” (bundle plug), and I think (but am not certain) that they were invented by the company now called Büschel Connecting Systems.

Multi-Contact’s specialty has always been the lantern style connector (“Lamellenstecker”), because of how it makes flat contact in multiple points.* (As opposed to the original Hirschmann banana plug, which made contact only in two spots, or the 2 or 4 contact points in a split pin). I don’t think MC ever made Büschelstecker type plugs.

I think I know the type of connector you’re thinking of, but it’s not a MC product.


* See https://docplayer.org/371035-1962-2012-50-jahre-multi-contact-ag.html which shows drawings of their earliest patent drawings, showing the internal lantern, and their first banana plugs, which are the rolled sheet type.

[Gyro]

I think your memory might be slightly confused.

I think you might be right, my memory is definitely fading. Yes, 'bunch plug' may well be closer.

I think I know the type of connector you’re thinking of, but it’s not a MC product.

Frustrating isn't it.

I wonder if anyone has experimented with spot welding one end of a standard lantern, it would eliminate the 'less satisfactory' of the contact areas.

[tooki]

What evidence is there of the standard lantern plug design being in any way deficient, when manufactured by a competent manufacturer?

[Gyro]

Wow, you're like a dog with a bone! No evidence, athough I have had tolerancing issues (lantern end slots closing too early) on the occasional cheaper one - predicting your answer, not everything comes with Stäubli or MC ones, or accomodates the cost.

By 'less satisfactory' I mean that, in contrast to the heavy wiping action and high point pressures of the outer lantern contacts, the inner is simply smooth contact sleeves contracting onto a smooth cylinder (ok with a little wiping action) but still with lower contact pressure per unit area. In the case of contamination, I would expect anything that gets inside the lantern to work itself down to those surfaces. If contact resistance were to increase, that's just where I would expect it to happen first.

As I say, absolutely no evidence of an issue with best quality connectors (ie. 'less satisfactory' = 'still satisfactory'), just 'engineering feel'. Neither of us knows how much the contact resistance would change if there was only one contact / plating interface rather than two. Permanently attaching one end of the lantern would also allow independent adjustment of insertion and withdrawal forces, depending on which end was secured - that could be a useful feature.

[tooki]

Wow, you're like a dog with a bone! No evidence, athough I have had tolerancing issues (lantern end slots closing too early) on the occasional cheaper one - predicting your answer, not everything comes with Stäubli or MC ones, or accomodates the cost.

Yeah but… I limited my comments to top-quality brands because your original claim was that the "best" lantern plugs had one end fixed.

[gamalot]

Sorry, I didn't fully understand what you were discussing, but I checked the banana plugs I used to make 4W-short (Stäubli Multi Contact 22.1055). Their lantern can be rotated (although it is really tight), and the lanterns on the banana plugs used on Fluke 5500A cannot be rotated.

[mawyatt]

Of all the various banana plugs we've used and have on hand, prefer the style shown above by Fluke. These just seem to have a larger surface area for the contact, and better contact to the inner plug.

The banana plug types and performance might make a good separate thread, would be very interesting to see which types have the best overall contact resistance and how well they stand up over time.

Best,

[tooki]

Of all the various banana plugs we've used and have on hand, prefer the style shown above by Fluke. These just seem to have a larger surface area for the contact, and better contact to the inner plug.

I don’t see how they would — they make contact to the socket in just 4 places. (And I don’t think you’d call them lantern style, though I don’t know what they are called!) The quality lantern makes contact on each of the little… slats I guess I’d call them. And because the lantern is compressed on insertion, it flattens the slats slightly when inserted, so they make even bigger contact. (And the twisted lantern even more so.)

The Fluke ones are, of course, Pomona, and I do like the Pomona plugs, too. But Stäubli and Hirschmann still win IMHO.

[gamalot]

Of all the various banana plugs we've used and have on hand, prefer the style shown above by Fluke. These just seem to have a larger surface area for the contact, and better contact to the inner plug.

The banana plug types and performance might make a good separate thread, would be very interesting to see which types have the best overall contact resistance and how well they stand up over time.

Best,

I did a simple test on my DIY short circuit using a Stäubli banana plug, compared it to the Fluke 5500A, and found no significant difference in thermal EMF and temperature coefficient.

I don't have a 3458 multimeter, my best meters are 6581T and 34465A.