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Offline hwj-dTopic starter

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EU - CalClub
« on: May 14, 2019, 03:22:25 pm »
What's the Idea of an EU-CalClub

look here:
https://www.eevblog.com/forum/metrology/eu-calclub/msg2420205/#msg2420205

After the USA Cal Club starts with a big members list thank Cellularmitosis, freshen up respectively become active with vindoline, some members and me ask for an EU-CalClub.

Ok, let us do that.  :-+

In the moment there are some uncalibrated LTZ1000 refs at my place that we can use. But, how I noticed, Andreas tries hard, to develop one 10V ref too. I don't know, it's a electronic concept or a real candidate for EU-CalClub? What I'm trying to say is, there are other members too, who have already dealt with the implementation of such a project, and it is therefore necessary to include all beforehand to put the whole thing on a firm footing. But it should be realized now.

I therefore suggest that topic to the Stuttgart meeting, so that we can better complete the idea there too and calibrate some refs and maybe resistors for that.

But nothing should stand in the way of the creation of a member list here and now. I like the star-shaped concept of sending with a random draw of a sequence.

Previous interested members like me in loose order till now are:

  • nnills
  • Echo88
  • mimmus78
  • bsdphk
  • bck
  • doktor pyta
  • MiDi
  • Sprock
  • borghese
  • Dr. Frank
  • Andreas
  • branadic
  • FriedLogic
  • pelule
  • Berni
  • SvanGool
  • 3roomlab
  • sipo75
  • sixtimesseven
  • alex-sh
  • e61_phil
  • meandeev
  • BU508A
  • cat87
  • BFX
  • wim.de.jong.59
  • Storm
  • zucca
  • ...

Anyone else?
Ideas?

Ok, everybody who thanked comes in the list.

cu,
H.-W.

« Last Edit: July 07, 2019, 10:15:57 am by hwj-d »
 

Offline bsdphk

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Re: EU - CalClub
« Reply #1 on: May 14, 2019, 03:44:31 pm »
I'm in.  (3458A, 732A)
 
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Offline bitseeker

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Re: EU - CalClub
« Reply #2 on: May 14, 2019, 05:03:01 pm »
Thanks for kicking this off, HW! :clap:
TEA is the way. | TEA Time channel
 
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Offline doktor pyta

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Re: EU - CalClub
« Reply #3 on: May 14, 2019, 05:04:52 pm »
I'm in.
D1281; SR104; SR1010 1k, 10R; 3x F732A; F845; F720A etc.
 
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Offline Echo88

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Re: EU - CalClub
« Reply #4 on: May 14, 2019, 06:16:11 pm »
 :)
3458A, 3456A, K2010, F720, K181, K155, F5440B, 2x 731B, 7x LTZ-Ref (yet unaged  :-[ ), 10Hz-1MHz-LAN, 0.1-10Hz-LNA, Scanner and Voltref in the making.
Im concerned about transportation-induced hysteresis in voltage/resistance-references.
Does somebody already have a working ovenized standard (for a LTZ-board for example) which could be used?
I have a few aluminium-cases which maybe would be suitable for resistance-standards/Refs and i could donate. Gotta take pictures.
 
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Offline hwj-dTopic starter

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Re: EU - CalClub
« Reply #5 on: May 14, 2019, 07:06:30 pm »
I built something like this with mini-pomonas. It's not finished yet. The resistors should still be on an aluminum block together with a PTC. If the whole thing fits flat enough into the lid, maybe even a ltz1000 ref with power pcb and standard pomonas will fit into. I also need a good 1M and 10M for this...
 

Offline branadic

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Re: EU - CalClub
« Reply #6 on: May 14, 2019, 07:37:22 pm »
Well, Frank had his LTZ references circling around last year or the year before? and found some shift. Okay, it was winter time and the references have not been thermally insulated during transport such as a styrofoam box. The only design I know of that is battery powered (NiMH) is from Andreas, but I fear the battery won't last for more then 2 days, so potentially a risk of power down if for some reason they need longer for shipment. I do have 3 of this references, but don't want them being shipped all over the place unless I transport them by myself because of this risk.
Even a Wavetek 7000 will only last for 16h (NiMH), a Fluke 732B for 72h (lead acid).
Andreas was also working on a battery powered AD587 reference, with selected reference. Sure enough it won't beat a LTZ or LTFLU reference in noise and stability. Correct me if I'm wrong Andreas.

So the only solution I see is a good thermal insulation for the reference in transport, such as multiple styrofoam boxes around the reference.

-branadic-
Computers exist to solve problems that we wouldn't have without them. AI exists to answer questions, we wouldn't ask without it.
 
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Offline hwj-dTopic starter

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Re: EU - CalClub
« Reply #7 on: May 14, 2019, 08:01:45 pm »
Then we should clarify which demand of quality standard we have at all for a turn arround reference. In my opinion, one of the px references as used in the usa cal club should suffice.
« Last Edit: May 14, 2019, 08:07:22 pm by hwj-d »
 

Offline Echo88

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Re: EU - CalClub
« Reply #8 on: May 14, 2019, 08:46:57 pm »
There are 11 732As at the moment on ebay.com. Lets buy one collectively and use it as EU-portable standard.  ;D ...
Very nice resistor-standard hwj-d  :-+
 
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Offline Andreas

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Re: EU - CalClub
« Reply #9 on: May 14, 2019, 08:49:50 pm »
Hello,

But, how I noticed, Andreas tries hard, to develop one 10V ref too.

Actually I planned to have one another traceable calibration on my AD587LW#02 on the meeting before sending it out.
It now has (hopefully) sufficient protection of the output so that it can survive the usual accidents.
I also have now 1 year of weekly measured ageing data which shows that the drift against my LTZs is below 1 ppm/year.

Im concerned about transportation-induced hysteresis in voltage/resistance-references.

That might be an issue. So my thought on this is sending it as a star pattern.
When I send it out on a monday the receiver should have it until the following week end for a measurement.
Returned on the following monday I should have it back the following week end for comparison with my LTZs.
So larger drifts (above the noise of my test setup) should be detected.

Andreas was also working on a battery powered AD587 reference, with selected reference. Sure enough it won't beat a LTZ or LTFLU reference in noise and stability.

Of course I would not try to adjust a 3458A with the AD587LW design.
(verification of the 10V range might be possible).
It is more intended to calibrate 6.5 digit instruments.

All in all my estimation is that it has maximum 5 ppm over one year and over a +/- 5 deg C range but this includes also some spurious short term (popcorn) noise. I have seen up to ~0.8 ppm during a one day measurement. Whereas the typical popcorn noise is around 1.5 uV which is within the 1/f noise level. Under good conditions we should get  ~2ppm stability.

The advantage is that it has rather low weight (< 1kg) and can be active ~1 week without recharging.

For the EU I will have to find a cheap option for sending since the "Deutsche Post" does no longer allow to send goods as letter which was a cheap option (7 EUR up to 1 kg). A international package doubles the rate.

Initially I wanted to check EMI stability (I have 2 different filter options on the PCB) before sending them out.
But I am still planning the measurement setup ... So I fear we will start before the EMI measurement is done.

with best regards

Andreas



 
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Offline hwj-dTopic starter

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Re: EU - CalClub
« Reply #10 on: May 14, 2019, 09:02:01 pm »
There are 11 732As at the moment on ebay.com. Lets buy one collectively and use it as EU-portable standard.  ;D ...
Ok, buy me one ...

Quote
Very nice resistor-standard hwj-d  :-+
Yes, understand. Need some help here ...  ;)
 

Offline Echo88

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Re: EU - CalClub
« Reply #11 on: May 14, 2019, 09:13:50 pm »
@hwj-d: Collectively as in 100€ from each participator to buy the 732A. But i fear the shipping-cost even within Germany, let alone EU, would be immense due to the size.
Dont know where to get 1M and 10M-resistors in the required quality. Maybe someone has such a WW-resistor from a Fluke 5450A or a TaN-hybrid from some torn down T&M-gear?

Edit: Looked in my resistor-spreadsheet and have seen that i have one 899.75k-WW-resistor from an old HP3420A and two 4.4987M-WW-Resistors from the same device. I suppose they are wirewound-resistors and both have +-0.2%-tolerance. They are a bit bigger than your resistor, but might fit in your case. Interested?
« Last Edit: May 14, 2019, 09:25:34 pm by Echo88 »
 
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Offline hwj-dTopic starter

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Re: EU - CalClub
« Reply #12 on: May 14, 2019, 09:31:29 pm »
Yeah, all right, all right. For that there are nice little px-references in nice little tekko's. That's enough to really get things rolling at the beginning of june.  ;)

The resistor standard should be a housing for a eu-ref, if that makes sense. :)
 

Offline hwj-dTopic starter

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Re: EU - CalClub
« Reply #13 on: May 14, 2019, 09:50:32 pm »
@Echo88
Just read the edit first. Thanks a lot for the offer, I appreciate it. But such a reference to send around does not necessarily still have to have 1M & 10M too.

No offence. My goal is to realize the eu-calclub as soon as possible now and where possible with the support of the stuttgart participants. Maybe we will see each other there.

Thanks  :-+
 

Offline Dr. Frank

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Re: EU - CalClub
« Reply #14 on: May 15, 2019, 06:45:36 am »
Hello,
we may discuss the stability problems in depth on the Metrology Meeting.
I've had bilateral exchanges of LTZ references and resistors already with a number of volt-nuts.

I usually have sent one LTZ1000, un-powered, and one VHP202Z, 10k, with built-in temperature sensor, allowing precise resistance calculation over temperature.

That fits in a small DHL packet at low cost.

Transfer is not possible during winter, as the LTZ especially at temperatures < 0°C shows hysteresis of several + ppm, but during spring .. harvest, it will retrace its nominal value within < 0.5ppm.

Round trip measurements are necessary to confirm successful transfers, as well as systematic data evaluation.

And yes, of course I would like to join this EU - CalClub, also by contributing references.

Frank
« Last Edit: May 15, 2019, 08:06:13 am by Dr. Frank »
 
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Offline MiDi

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Re: EU - CalClub
« Reply #15 on: May 15, 2019, 08:55:38 am »
Highly appreciated and thanks hwj-d to start this!
Count me in.

3458A, 7081, 3xLTZ1000 branadic, Z201 Resistance box (all uncalibrated)
 
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Offline Echo88

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Re: EU - CalClub
« Reply #16 on: May 15, 2019, 10:02:06 am »
I have a few of the mentioned aluminium-cases which id like to donate for the Cal-Club. Suitable for 100mm wide standard-pcbs, case is 120mm deep.
Pretty, but not the best regarding shielding though, since they are anodized.
https://pasteboard.co/IeNkPx8.jpg
 

Offline pelule

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Re: EU - CalClub
« Reply #17 on: May 15, 2019, 03:41:09 pm »
OK - Add me to the list, having following equipments (and more):
  • DMM 8.5 digits: HP 3458A, 2x Datron 1281
  • DMM 6.5 digits: HP 34401A, HP 3456A, HP 3455A, Fluke 8506A, Keithley 2000
  • V-Ref: Fluke 731B, Fluke 3330B, HP 735A, Guidline 9152TP4
  • R-Ref: Fluke 5450A
  • Temp: PREMA3040
That proofs it - I am a volt-nut  |O
You will learn something new every single day
 
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Offline hwj-dTopic starter

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Re: EU - CalClub
« Reply #18 on: May 15, 2019, 04:40:28 pm »
I have a few of the mentioned aluminium-cases which id like to donate for the Cal-Club. Suitable for 100mm wide standard-pcbs, case is 120mm deep.
Pretty, but not the best regarding shielding though, since they are anodized.
https://pasteboard.co/IeNkPx8.jpg
Are you in Stuttgart? Bring them with you.  :)
 

Offline Berni

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Re: EU - CalClub
« Reply #19 on: May 15, 2019, 04:56:09 pm »
I have a good few multimeters around me and in the EU.

8.5 digit: Keithley 2002, HP 3458A
6.5 digit: Keithley 2015, Keyithley 2100, Keithley 2750, Agilent 34461A, Agilent 34401A

Some of these multimeters are also for sale.
 
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Offline Echo88

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Re: EU - CalClub
« Reply #20 on: May 15, 2019, 08:06:22 pm »
I cant attend the meeting this year. But i can send the enclosures to the people who wish to use them for the calclub.
 

Offline FriedLogic

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Re: EU - CalClub
« Reply #21 on: May 17, 2019, 07:29:55 am »
Transfer is not possible during winter, as the LTZ especially at temperatures < 0°C shows hysteresis of several + ppm, but during spring .. harvest, it will retrace its nominal value within < 0.5ppm.

Hi,
Did you notice this happening repeatedly or with different references? I'm just wondering if this is a fundamental issue, or one which can be fixed or reduced by things like component selection, circuit design, processing and usage.
 

Offline Dr. Frank

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Re: EU - CalClub
« Reply #22 on: May 17, 2019, 08:22:18 am »

Hi,
Did you notice this happening repeatedly or with different references? I'm just wondering if this is a fundamental issue, or one which can be fixed or reduced by things like component selection, circuit design, processing and usage.

This hysteresis is a fundamental feature of the LTZ1000 reference chip itself.
Description can be found in the Pickering patent, and also in different papers about his Datron / Fluke 7000 reference.
Another hint is inside hp SN-18, where they describe relaxation effects of their LTZ1000A references, which is a secondary consequence of hysteresis.

I observed that effect on 4 of my LTZ1000 references experimentally, 2 of them where sent in winter, when outside temperatures were below zero °C.
For the other 2 references, I cycled them between -20°C and +80°C with decreasing temperature swing, and could bring both back to original value.

After excursion to low temperatures, the reference voltage will always go up by several ppm, and high temperatures will force it to lower values.

Quite obviously, you can't do anything in the external circuit to mitigate that effect.

There were several assumptions in the LTZ1000 thread, that the A type is less prone to this hysteresis, due to the different, assumed more flexible assembly of the chip to the case.
I've never seen any experimental proof or quantitative measurement for that assumption, so at current, this is simply incorrect... SN-18 also indicates, that the A version is affected as well.

This hysteresis effect is equivalent to the magnetization of iron. Therefore, it is not possible to use something like a 'burn in' process to eliminate this hysteresis for all times.
But as described in this patent, it's possible to temperature-cycle the chip to its 'virgin' state.
If you want low timely drift, you need to run the oven at 45..65°C. The 7000 reference, like the 732 A/B all run at 45°C.
Therefore, this Pickering patent does not work properly inside the 7000 references, as a symmetrical temperature swing of initial +/- 40°C cannot be  accomplished.

Unfortunately, the rare owners of this device, like TiN, did not yet measure the real oven temperature, and also not the cycling profile.
Otherwise, we also could design this scheme into our existing references... as far as it's really working.

At current, it's only possible to log the temperature during transport, and to compare the reference value before and after shipping.
Hot shipping is the alternative method, with the known disadvantages and shortcomings.

Frank
« Last Edit: May 17, 2019, 08:50:23 am by Dr. Frank »
 
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Offline TiN

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Re: EU - CalClub
« Reply #23 on: May 17, 2019, 11:29:41 am »
Unfortunately, the rare owners of this device, like TiN, did not yet measure the real oven temperature, and also not the cycling profile.
Otherwise, we also could design this scheme into our existing references... as far as it's really working.

That is a bit understatement, but yes, I'm guilty of not showing W7000 love.. I still hope to find time for complete reverse-engineering, so I don't have it closed up still, to do proper measurements.
But I did perform measurement of power on conditioning cycles year ago.





I'm not very happy with it, my last try to measure it's tempco (10V) provided wierd results that made no sense. And switching charger/isolated power supply emit nasty squeak which I can hear across the room. Don't like switching power supply next to reference board even single bit.

Used setup:



[/offtopic]
« Last Edit: May 17, 2019, 11:33:03 am by TiN »
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Offline Dr. Frank

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Re: EU - CalClub
« Reply #24 on: May 17, 2019, 12:05:47 pm »
Unfortunately, the rare owners of this device, like TiN, did not yet measure the real oven temperature, and also not the cycling profile.
Otherwise, we also could design this scheme into our existing references... as far as it's really working.

That is a bit understatement, but yes, I'm guilty of not showing W7000 love.. I still hope to find time for complete reverse-engineering, so I don't have it closed up still, to do proper measurements.
But I did perform measurement of power on conditioning cycles year ago.


I'm not very happy with it, my last try to measure it's tempco (10V) provided wierd results that made no sense. And switching charger/isolated power supply emit nasty squeak which I can hear across the room. Don't like switching power supply next to reference board even single bit.

Used setup:


[/offtopic]

Hi Illya,

your measurements of the output swing, and a similar one from e61_phil, really do not indicate the real temperature swing!

In your measurement, the reference swings symmetrically by +/- 8500ppm.
The T.C. of the LTZ1000 is about 55ppm/k, therefore, that would mean a swing of  +/-155°C.

Similarily, in the patent as an example, a change of +/- 80mV of the Ube of the reference diode is shown, giving +/- 40°C, but at an oven temperature of 80°C, so it could swing between +40 and +120°C, which does not fit the final realization of 45°C oven temperature.

I'd like to ask you to simply monitor the Ube of your 7000 reference, which is really easily to be measured.

If you digitize that voltage during power up, you can calculate oven temp, and measuring it during the cycling process, you can directly measure the swing profile.

Frank
 


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