Ultra Precision Reference LTZ1000

[lukier]

You are right, good cables are important. But to be honest, 100€ and more for a ready to go 1m PTFE cable with gold-plated spade lugs or simple Multi Contact (former Staubli) connectors are half the budget of a LTZ reference und pretty expensive. I'm still searching for an economic solution or a source for good twisted pair, shielded PTFE cable. This is what I took for homework to be done until next meeting. 

You don't need to spend 100€/m. Well maybe off the shelf Fluke cables cost that much, but things can be DIY-ed for much less, not to mention that Cat6 ethernet cable would be probably good enough.

If the group in Germany is big enough one could do a group buy a 150m reel and split the cost:
https://www.mouser.co.uk/ProductDetail/Belden-Wire-Cable/8719-060500?qs=sGAEpiMZZMs5%2f3jTaGtq4K0qP2YKd7fbUuidhOjrEF0%3d

From time to time one can find off-cuts on eBay like I did recently:
https://www.ebay.com/itm/192406299624

All in all I've paid 88.02 GBP for 17m (too much), so ~5.17 GBP/m. One would need < 3m for a DIY Fluke 5440A-7003 (based on this cable), so ~12.5 GBP,  4.56 GBP for two Pomona 1825-6 and few quid more for copper spades and thermal shrink tubes. That is probably < 25 GBP for a set of 3 cables almost identical to what Fluke uses for 732B. Not pure copper, not PTFE, but good enough for Fluke it seems. See the photo (I'm waiting for guard Pomonas from Mouser). This is some heavy cable, should be good enough up to 10A as well.

I have some 4 wire PTFE coming my way from eBay (again off-cuts) for high resistance / low current stuff. It is also around 5-6 GBP/m (all in all, shipping, taxes). I'll share more when it gets here and I'll make some leads.

[branadic]

Beer + calibrated references + expensive DMMs = the European equivalent of "Hey, y'all, watch this"?   

The DMMs are not private, but part of the calibrated equipment at my work. So we can use it to compare our homebrew stuff to get the volt at home. What else do you want?

-branadic-

[exe]

How does transportation affect precision? Are ltz1000 sensitive to vibrations and (big) change of temperature?

[branadic]

vYou don't need to spend 100€/m. Well maybe off the shelf Fluke cables cost that much, but things can be DIY-ed for much less, not to mention that Cat6 ethernet cable would be probably good enough.

Thanks for sharing.

At least the reference design by Andreas uses a battery pack to power them during transportation. The inguard with the resistors and reference is thermally isolated with cotton wool.
To reduce temperature effects I had them in a "cooling" bag during transportation and thus good isolated from ambient temperature.

-branadic-

[Andreas]

How does transportation affect precision? Are ltz1000 sensitive to vibrations and (big) change of temperature?

Hello,

since I transport my LTZs hot they are less affected by temperature.

I also check them before and after transport against my 24 Bit ADCs.
Up to now no issue found outside the stability of my ADCs (around 0.25 ppm std dev).

So it is more risk to transport a LTZ1000 or  a complete 3458A in cold state in winter.
(see reports of Frank here e.g.)
https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg1882325/#msg1882325


with best regards

Andreas

[Dr. Frank]

Folks, please calm down!

The quality of these leads maybe not so good, but volt-nuts meetings should be appreciated, anyhow.
Especially, if the scope of this comparison is still to be analysed.

A German engineering meeting w/o beer, that's another serious story.. that has to be improved! Illya, what's your favorite booze?

In the company, we recently had our international engineering meeting from our 10 development sites, from 4 different continents (Australia has no Engineering anymore, sorry Dave), and German beer was the most important feature.

I also can add, at the latest volt-nuts meeting @ Andreas and with branadic , I carried my 3458A.

Afterwards, due to the transport, it showed a jump of -0.5ppm. It was not that cold at all, like the latest LTZ comparison last year, of two of my LTZ1000 (unheated), so most probaly, that simply was caused by vibration.

I was able to definitely identify that by comparison to the home-residing references (2x LTZ1000, 1x 5442A)

Anyhow, (cold) transportation and vibration is not yet examined well, inside this thread..

Andreas' approach are heated references, mine are potentially unheated ones, during transport.

Pitiful, we did not do that complete ring-comparison yet.

There are a lot of people here in Germany and EU to organize LTZ1000 and 10k Ohm exchange, but somehow there's no real drive to just do it, by DHL, or personally...

Instead of moaning at each other, maybe we could organize something international, even using quality references, as LTZs and VHPs.

Frank

[Macbeth]

It looks like you guys all had some fun. Besides, I've always found the "teflon coated pure copper cable with crimped lugs mating with purest tellurium copper posts" a bit like audiophool wankery. I mean it also requires the environment to be totally sterile, no draughts, changes of temp, and just so the Seebeck effect is cancelled out after plugging leads in a mere 2 seconds vs 30 seconds (totally made up) with inferior brass posts and connections?

Ok, if you are in a factory calibration situation like a US army post, drilling through 10's or 100's per day, then a fast connection get the job done, shift it, move on to next job is the order of the day. The grunt will not care so expensive low thermal leads are easily justified here.

But in your own lab or a get together?? Just needs some time to settle.

I am also only a 6.5 digit nut. 

[GregDunn]

A German engineering meeting w/o beer, that's another serious story.. that has to be improved! Illya, what's your favorite booze?

In the company, we recently had our international engineering meeting from our 10 development sites, from 4 different continents (Australia has no Engineering anymore, sorry Dave), and German beer was the most important feature.

I'll have to settle for raising a virtual toast from my end - but give me time to visit the nearest Hofbräuhaus and collect some nice Oktoberfest brew before the next volt-nut meeting so I can celebrate accordingly!

[TiN]

The quality of these leads maybe not so good, but volt-nuts meetings should be appreciated, anyhow.

Indeed, the more meetings the better.  I still remember lots of fun during my 1 week meet-up in US 2 years ago, we should make it happen again in 2019 with US nuts.
My comment was just a hint on areas to improve, perhaps it was lost in language/cultural differentials. No need spend hundreds of dollars/euros/pounds to get CAT6e shielded cable and benefit the low-thermal connections to the 3458A's posts, and get rid of those laptops full of switching power supplies. I design computer hardware for living, so I know how much crap does this stuff emit for RFI/EMI first hand . Little improvements and care like that pay off by better confidence in results.
Or maybe I played with nanovoltmeters too much, where using even different copper cable is well visible... 

There are a lot of people here in Germany and EU to organize LTZ1000 and 10k Ohm exchange, but somehow there's no real drive to just do it, by DHL, or personally...
Instead of moaning at each other, maybe we could organize something international, even using quality references, as LTZs and VHPs.

I'd love to get some refs rotated (or DMMs, as my calibrator is already happy and in order). But I fear we'll run into same issue as USA Cal club thread members, with undefined procedures and lack of data transparency. Often amount of work to even perform single reference transfer round-trip in terms of careful math, environment effect accounting and drift prediction is underestimated. While that's all fine for 6.5digits, getting numbers up to 8.5d level is whole other story, outside of this thread topic.

[MiDi]

You are right, good cables are important. But to be honest, 100€ and more for a ready to go 1m PTFE cable with gold-plated spade lugs or simple Multi Contact (former Staubli) connectors are half the budget of a LTZ reference und pretty expensive. I'm still searching for an economic solution or a source for good twisted pair, shielded PTFE cable. This is what I took for homework to be done until next meeting. 

ab-precision has fully assembled low emf, diy-kits and 2/4 wire teflon cable - everything a low-emf heart desires  (not affiliated)

A year ago I got a pair of self-made 2/4wire ptfe low emf (45/50Eur) from german ebay-seller sd-trader, but at the moment there are no items...



Low EMF comes at a price, even the Pomona 3770 are quite expensive: ~15$ each 

[MikeP]

 Regarding cheap CuTe connectors - FUREZ. This is a recommendation of some metrological  specialist. I used this and can confirm good quality.

[Echo88]

Those Furez-connectors: https://www.douglasconnection.com/Furez-Products_c20.htm
look rather good, but lack the possibilty to directly be crimped on copper wires and have a big thermal mass.
I rather stay with the spade-lug-version mentioned by MiDi.

[VK5RC]

The Aussie volt-nuts did a reference shuffle about a year ago, certainly a lot of lessons were learnt. In my set up, a laptop in the lab anywhere is pretty bad, 10-20uV change, esp if connected by gpib, more so if running on the charger.
The travel of the references - probably a mixture of road and air- I think also wasn't good.
For my longer term (11 months to date) reference measurements, 9  KZ  LTZs, one old 3458 ref board and a Fluke 731b.
I have used exclusively one (and only one actual cable) of Pomona's low emf shielded cables - I have been very happy with the consistency of the results.
6 of DrFranks LTZs are in the pipeline, 3 using a 'quick and dirty' mixture of vishay (120Rs) & TEs , and 3 awaiting some Edwin goodness!

[MikeP]

but lack the possibilty to directly be crimped on copper wires

 No. This connectors can be crimped very well. In addition, e >:Dbay offers this brand very inexpensive.

[Echo88]

Must have overlooked the crimp-type-ones and only did see the ones with the tightening screws. Indeed, they look price-wise not bad compared to the standard Pomona 3770-binding posts:

https://www.ebay.com/itm/Furez-TST-W30AG-Silver-Plated-Copper-Banana-Plug-Speaker-Connectors-Crimp-Solder/142938936767?hash=item2147d315bf:g:ZlQAAOSwfLpbnEgS:rk:17:pf:0

[splin]

Silver oxidizes fairly quickly in air which I assume would be terrible for thermal EMFs. If you are going to have to clean them before every use why not stick to unplated copper?

Do Furez do gold plated copper plugs?

[ManateeMafia]

I have some of these https://www.douglasconnection.com/Furez-TSTWP30NP-Bare-Copper-Banana-Plug-Connectors-Pair-FZTSTWP30NP.htm I use for a Keithley 181 cable.

They are nice but do scratch easily if the binding posts are not clean.

[branadic]

What is a resin printer such as Anycubic Photon worth for? Exact, for printing LTZ caps. Did that today.

Offer: I also printed those HP/A/K LTZ1000 caps, but they don't fit to this board or any other board I have. The one who writes me a PN first can get those two caps for postage cost only. Will also add the bottom cap, that I print the next days.

Attention: Please check your LTZ boards for short circuits. Someone reported a pretty big short on one of his boards. I haven't checked all the boards, just packaged them and sent them out.

-branadic-

[exe]

BTW, I wonder why lt1013 is used and not, say, LT1001 . LT1001 has lower offset. Sorry if this was discussed before.

Is LT1001 auto-zero op-amp? This could explain why people don't use it. The datasheet doesn't mention this.

[borghese]

The minimum input voltage of LT1001 is > 1 Volt; in normal LTZ circuit the voltage is about 0.5 Volt.
NO, the LT1001 is not Auto-zero OP. 

[borghese]

What is a resin printer such as Anycubic Photon worth for? Exact, for printing LTZ caps. Did that today.

Hello
Can you share the CAD files?

[branadic]

What is a resin printer such as Anycubic Photon worth for? Exact, for printing LTZ caps. Did that today.

Hello
Can you share the CAD files?

Which one do you mean, the HP/A/K? They can be found here:

https://xdevs.com/doc/HP_Agilent_Keysight/3458A/cad/a9_cap_top.STEP
https://xdevs.com/doc/HP_Agilent_Keysight/3458A/cad/a9_cap_bot.STEP

Or do you mean the one I designed?

-branadic-

[borghese]

The one you designed.
Thank you in advance.

[branadic]

The caps are given away. Congrats to the new owner.

-branadic-

[dkozel]

borghese, there's a zip attached to branadic's previous post. I don't have an stp file viewer, but it's almost certainly his caps.