L@@KING for gold-plated tellurium-copper banana plugs

[DiligentMinds.com]

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[quarks]

Hello Ken,
I have done a lot of research, tests and measurements about low EMF connections.
https://www.eevblog.com/forum/buysellwanted/diy-low-emf-cable-and-connectors/msg190302/#msg190302

I also looked for an adapter for my Tek DMM 4050 and have only found and bought the 884x-short. If you had the same result, you probably have to build/modify something yourself.  Good candidate CuTe binding posts are from Pomona (3770), Multi-Contact (PK4-TS), IET (BP1000) and jswilley (2758). I also tested banana plugs with screws. The Multi-Contact (LS425-AM and LS425-SE/M) are not CuTe, but nevertheless they showed very good results.

Bye
quarks

[robrenz]

I made a super short pictured here.  .625 diameter tellurium copper bar with these gold plated beryllium copper banana jacks.
But all the jacks I have found including these only the spring element is beryllium copper, the bodies are gold plated brass. But the total min max span of a 152 hour shorted input stability test on my 8846A using this was only 1µV. There was a 2.4 degree C temperature variation over that time so I don't think thermal emf's of the gold plated brass were a big issue. I think in this case a larger mass short like this is more stable because it is influenced less by short term temperature swings.

[quarks]

for fast equilibrium you have to have as low as possible mass. So the plug comes as fast as possible to the same temp as the connector of the DMM.There is a very good Fluke paper with the Fluke 8508A and I have done my tests exactly how it is shown in this paper.

[eKretz]

I read an article about a similar thing (thermoelectric error). Higher mass shorts tend to introduce EMF errors, check it out, the relevant article starts on page 20 IIRC. In the article, one of the best shorts they tried was just a small piece of solid copper telephone gage wire.

http://www.callabmag.com/wp-content/uploads/2012/06/apr12.pdf

[quarks]

That is exactly the article I have downloaded from the Fluke site.
http://us.flukecal.com/literature/electrical-calibration/watch-out-those-thermoelectric-voltages-cal-lab-journal-reprint

att. is a picture of some of the tested connectors

[robrenz]

I am familiar with that article and it is not stating that a large mass ohmic zero is inherently less accurate but just that it takes a long time to thermally stabilize with the meter. A low mass "Thermal zero" is only good if you have extremely low currents involved. From the article: "Ohmic zeros have very small actual resistance so the measurement value is truly a zero without any unwanted offsets caused by I times R losses based on the current supplied by the meter and the physical resistance of the shorting device. (For example, milliamps of current through milliohms of resistance create microvolts of unwanted measurement voltage.)"  In This post and several following it I discovered that the resistance of an "Ohmic zero" is  a big deal if high currents are involved as in testing the compliance voltage of a power supply in CC mode. Since time to stabilize is not an issue for me and that once stabilized it is less influenced by any short term temp fluctuations I use it for all testing.

[robrenz]

I can make solid telurium copper dual or quad binding post to banana adapters.  You could then plug this into a flush  style meter and use all you low emf spade terminal items or wires in the binding post holes. Having them coupled in a dual or quad arangement will allow tightening of the binding post nuts.

If there is enough interest I can figure out what they would cost based on how many are needed.

[quarks]

hello robrenz,
that is a great idea. With my limited machinist skills, I would think of an adapter like this (see att.) and I would leave it always pluged in (unless/until I need the security plugs)

[robrenz]

Yes like that but much shorter. The banana would stop at a piece of 3mm plastic that tied the posts (2 or 4) together and the binding post shoulder would start right at the other side. That would make it very close coupled so the binding post shoulder would only be about 4mm from the face of the meter.  This is important so the banana jacks in the meter are not strained by a large lever arm like the one you showed. This would also be one piece copper construction where there is no separate spring contact on the banana jack. it would be multi finger with an elastomeric expander plug inside the fingers to provide the contact pressure.

[quarks]

that sounds very good to me.
Maybe that is also an idea, look at the att. picture. Inside the plug is a screw that will widen the slotted ends

[robrenz]

I assume you are talking about the one on the right and it is too out of focus to tell what is going on.

[Rufus]

That is exactly the article I have downloaded from the Fluke site.
http://us.flukecal.com/literature/electrical-calibration/watch-out-those-thermoelectric-voltages-cal-lab-journal-reprint

The article is kinda crap showing the sadly common misunderstanding of how thermal emfs are generated.

Thermal emfs are not generated across junctions - junctions are dead shorts. Having any significant temperature difference between two metals forming an electrical connection is equally impossible. The junction can be considered to be almost infinitesimally thin and so have almost infinitesimally small thermal resistance.

[quarks]

I assume you are talking about the one on the right and it is too out of focus to tell what is going on.

no they are both the same (just red and black).
They are just the reverse of what we talk about, because they are adapters for binding posts to be able to plug in security bananas. But the mechanisem inside could be also usefull for the wanted adapter.

[ConKbot]

That is exactly the article I have downloaded from the Fluke site.
http://us.flukecal.com/literature/electrical-calibration/watch-out-those-thermoelectric-voltages-cal-lab-journal-reprint

The article is kinda crap showing the sadly common misunderstanding of how thermal emfs are generated.

Thermal emfs are not generated across junctions - junctions are dead shorts. Having any significant temperature difference between two metals forming an electrical connection is equally impossible. The junction can be considered to be almost infinitesimally thin and so have almost infinitesimally small thermal resistance.

Would you be alluding to that thermal EMF is generated across thermal gradients rather than junctions? 

[robrenz]

That is exactly the article I have downloaded from the Fluke site.
http://us.flukecal.com/literature/electrical-calibration/watch-out-those-thermoelectric-voltages-cal-lab-journal-reprint

The article is kinda crap showing the sadly common misunderstanding of how thermal emfs are generated.

Thermal emfs are not generated across junctions - junctions are dead shorts. Having any significant temperature difference between two metals forming an electrical connection is equally impossible. The junction can be considered to be almost infinitesimally thin and so have almost infinitesimally small thermal resistance.

Would you be alluding to that thermal EMF is generated across thermal gradients rather than junctions?

I am of the same opinion, from what I have studied the thermal gradient in a conductor is what causes an emf. the junction itself does not cause the emf. This does not contradict how thermocouples work. In my opinion you can ignore platings because they are so thin that the thermal gradient across the plating would be insignificant.  But copper vs copper oxide show that there may be some kind of semiconductor effects of a junction itself.  I have been meaning to bring this very topic up  to get feedback from those more knowlegeable on the topic.

[robrenz]

I assume you are talking about the one on the right and it is too out of focus to tell what is going on.

no they are both the same (just red and black).
They are just the reverse of what we talk about, because they are adapters for binding posts to be able to plug in security bananas. But the mechanisem inside could be also usefull for the wanted adapter.

I could make them to do the same thing with the expander screw acessable thru the banana jack of the binding post

[alm]

I haven't studied the physics of the Seebeck effect at all, but my guess is that it has to do with how temperature affects how easy it is for electrons to enter the conductance band. The electrons have to jump to different energy levels as they transition between different metals, and I imagine this may be temperature dependent. If this is true, then even a coating of one atom thick should have an effect. This would also be consistent with the large effect of copper oxide.

You always need two junctions for thermocouples (which use exactly the same physics): the hot junction and the cold junction. Energy flows from the hot junction to the cold junction. The hot junction could for example be the copper-nickel junction at the positive input terminal, and the cold junction could be at the negative input terminal which is 0.5 K colder because it's directly connected to the case (random example). The current flows between the two junctions (terminals), causing an offset voltage.

[Rufus]

Would you be alluding to that thermal EMF is generated across thermal gradients rather than junctions?

Thermal emf is generated everywhere within a conductor. Proportional to temperature (not linearly) and quantified by the seebeck coefficient of the material.

If one end of a conductor is hotter than the other there will be a net difference of thermal emf between the ends. The trouble is you can't measure it without connecting some more conductors which must also have some temperature difference between their ends and possibly different seebeck coefficients. Connections require junctions but the junctions have nothing to do with generation of the emf.

If you deliberately choose to connect conductors with different seebeck coefficients at the 'cold' end you see an emf due to the different seebeck coefficients which is proportional to the difference in temperature between the ends and you call it a thermocouple.

If you choose to connect conductors with the same seebeck coefficients then the emfs cancel out and you see nothing at the 'cold' end. If you use the same material you could argue there are no junctions but that isn't why you see no emf.

[robrenz]

What Rufus said is exactly my understanding also.

[robrenz]

This paper attached is what helped form my opinion. i will post others as soon as I find them.

@ DiligentMinds.com   Would you like us to start another thread on this instead of crashing here?

[Rufus]

I haven't studied the physics of the Seebeck effect at all, but my guess is that it has to do with how temperature affects how easy it is for electrons to enter the conductance band.

My non-physicist never studied it theory would be the hotter the material is the more the electrons move around. The average repulsive force between them is larger because moving around more they get closer to each other.  Hot electrons want to occupy more space than cold ones.

[quarks]

just saw this

http://translate.google.de/translate?hl=de&sl=sk&tl=en&u=http%3A%2F%2Fwww.elsocz.cz%2Fvodice-hroty-svorky%2F2733-adapter-na-pripojenie-vodicov-do-4mm-zdierok-elso-gw4a.html

[robrenz]

They look nice but It does not say what the material under the gold plating is.  And that goes back to my question of how much thermal EMF effect can the plating have at such thin layers and no one seems interested in discussing that topic

[SArepairman]

can you just bend a piece of thick copper wire to make a U shape?