EU - CalClub

[hwj-d]

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.

[bsdphk]

I'm in.  (3458A, 732A)

[bitseeker]

Thanks for kicking this off, HW!

[doktor pyta]

I'm in.
D1281; SR104; SR1010 1k, 10R; 3x F732A; F845; F720A etc.

[Echo88]

 
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.

[hwj-d]

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...

[branadic]

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-

[hwj-d]

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.

[Echo88]

There are 11 732As at the moment on ebay.com. Lets buy one collectively and use it as EU-portable standard.  ...
Very nice resistor-standard hwj-d 

[Andreas]

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

[hwj-d]

There are 11 732As at the moment on ebay.com. Lets buy one collectively and use it as EU-portable standard.  ...

Ok, buy me one ...

Very nice resistor-standard hwj-d 

Yes, understand. Need some help here ... 

[Echo88]

@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?

[hwj-d]

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.

[hwj-d]

@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 

[Dr. Frank]

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

[MiDi]

Highly appreciated and thanks hwj-d to start this!
Count me in.

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

[Echo88]

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

[pelule]

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 

[hwj-d]

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. 

[Berni]

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.

[Echo88]

I cant attend the meeting this year. But i can send the enclosures to the people who wish to use them for the calclub.

[FriedLogic]

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.

[Dr. Frank]

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

[TiN]

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]

[Dr. Frank]

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

[TiN]

Maybe we start separate thread on this? As where did you get 55ppm/K figure? I recently stress-tested LTZ1000A ref (chamber temp outside of oven setpoint) and got much smaller TC, around 3ppm/K. If the real swing would be near +/-155C that would mean LTZ die will be very much dead already.

I will get to it, but all my meters are currently busy characterizing FXes, need to get these shipped to EEVBlog members already, including members of EU Club. 

EDIT: Wrong terminology used, stuff I measured was NOT the unheated-zener tempco.

[Dr. Frank]

Maybe we start separate thread on this? As where did you get 55ppm/K figure? I recently stress-tested LTZ1000A ref (chamber temp outside of oven setpoint) and got much smaller TC, around 3ppm/K. If the real swing would be near +/-155C that would mean LTZ die will be very much dead already.

I will get to it, but all my meters are currently busy characterizing FXes, need to get these shipped to EEVBlog members already, including members of EU Club. 

Hello Illya,

measurement technique and T.C. determination are here: https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg1336575/#msg1336575

That ~ +55ppm/K was also confirmed by other volt-nuts, but I can't find the link at the moment.

I doubt that you correctly measured these 3ppm/K.

Anyhow, something else happens in the 7000s cycling process, than only the change of the oven temperature. To find out, you really need to measure directly this Ube of the reference element. Maybe your 3ppm/K measurement was done at the Ube of the transistor of the oven control circuit, instead ?!

Frank

[SvanGool]

...
Hot shipping is the alternative method, with the known disadvantages and shortcomings.
...

Hot shipping under constant temperature, generically, also for portable resistor-references, is a brain project of mine. The advantages, assuming that one can also take care of humidity stabilization (e.g. using silica gel method):

• Much lesser temperature fluctuations and therefor much lesser TC dependability
• Reproducibility of accuracy in different environmental conditions, with supplied cables and connectors and when load conditions are met

The disadvantages, I can think off:

• Power need, will require a substantial battery pack (preferably non Li-Ion because of shipping limitations)
• Weight and size
• Is it allowed to ship a "hot" device?
• Needs an accurate oven circuitry and isolation

Ideally this would be a 23°C device, but then you need heating and cooling. Otherwise a 45°C should do for a heating-only device. It should be possible to have a PPMish reproducible accuracy and a PPMish long term stability.
I also know that a lot of people will classify this as "cannot be done as diy, look at what is needed for a 732A", but I didn't hear very strong arguments yet of not achieving this by putting an LTZ1000xxx and a few hermetic VPGs in such a device.

Any suggestions/comments/laughs?

[Dr. Frank]

...
Hot shipping is the alternative method, with the known disadvantages and shortcomings.
...

Hot shipping under constant temperature, generically, also for portable resistor-references, is a brain project of mine. The advantages, assuming that one can also take care of humidity stabilization (e.g. using silica gel method):

• Much lesser temperature fluctuations and therefor much lesser TC dependability
• Reproducibility of accuracy in different environmental conditions, with supplied cables and connectors and when load conditions are met

The disadvantages, I can think off:

• Power need, will require a substantial battery pack (preferably non Li-Ion because of shipping limitations)
• Weight and size
• Is it allowed to ship a "hot" device?
• Needs an accurate oven circuitry and isolation

Ideally this would be a 23°C device, but then you need heating and cooling. Otherwise a 45°C should do for a heating-only device. It should be possible to have a PPMish reproducible accuracy and a PPMish long term stability.
I also know that a lot of people will classify this as "cannot be done as diy, look at what is needed for a 732A", but I didn't hear very strong arguments yet of not achieving this by putting an LTZ1000xxx and a few hermetic VPGs in such a device.

Any suggestions/comments/laughs?

we (e61_phil and I) already did successful tests on hot shipping on his 'bread box' reference assembly.
Very massive and heavy, but very long lasting battery.

Unlike the 732A/B, it is not necessary at all to build another oven around the whole PCB.
Just to continuously heat the LTZ1000 oven, and of course power the whole reference circuit (~25mA @ 12V) is enough.
The other components of the reference circuit do not have an impact on the hysteresis, and if trimmed to near zero T.C., also do not influence the absolute output voltage of the LTZ1000 over temperature.

Everything else is complete over-engineering.  In another use case, you would also intend to temperature stabilize the 10V upscaling resistor divider.

I'd like to refer to the LTZ1000 thread, where < 1ppm stabilities (over time, temperature, noise) have been experimentally demonstrated already, by many 'amateur' volt-nuts, despite the (unproven) statements of a few naysayers.

Frank

[Berni]

12mA at 12V is actually not that bad. But im guessing this is heavily dependent on the ambient temperature and how well insulated the thing is. Gonna take heck of a lot more power to keep it warm at -10°C ambient compared to 30°C ambient wrapped in a bunch of insulation.

But going off that number that is 150mW of power. So running it for 3 weeks would consume 75Wh of energy. With the typical Li-Ion energy density of 200Wh/kg this would take a 380g battery. Safer types such as LiFePO or Ni-MH have about half the density at about 100Wh/h making the required battery about 750g. So yeah lugging a battery along would indeed add quite a bit of shipping cost, but can still be kept under 1kg.

Oh and what about any potential package x-ray scans? Since high energy radiation is known to have effects on semiconductors, would that upset its stability?

[babysitter]

Besides investing in isolation of the box, how about non-ohmic, non-peltier heating? Adding chicken to the package (Blue peacock bomb, anyone?) might be overengineering, too.

But how about slow exothermic chemical processes? Think of the hand warmers, but slower. Calcium oxide getting only very little water over shipping time? Or actually biological processes? It shouldn't emit anything nasty, of course, no one wants the shipped artifact full of rust. Dang, lets control the exothermic process by electronic sensing - logging might be a good idea anyway.

BR
Hendrik

[hwj-d]

Hmm ..   

very interesting positions, what an eu-calclub reference that can be sent all around should have in terms of properties. 

It seems to be fixed, there is not only one maybe two reference(s) with one transmitter and one receiver like usa cal club in the moment. No, there are many references with many transmitters and many receivers, that shouldn't be not that problem (many to many). It gets more problematic when many transmitters and many receivers also have many different ideas about what the respective reference should do for their respective interests ('nay' sayer vs 'beginner' vs real heavy voltnuts, but not in wintertime, but keep it small, but heavy isolation, and more...).

My concluson (and proposal) is:
 do what you can do in the real moment, but
   keep it simple!

 

[Echo88]

@babysitter: You could use Paraffin which uses its latent heat to warm the ref to ~40°C, depending on used Paraffin-type.

[FriedLogic]

My concluson (and proposal) is:
 do what you can do in the real moment, but
   keep it simple!

That would be my thought too. There are all sorts of options for a reference which can be put in the boot of a car and driven around, but a small ref to mail around is another thing.

(and thanks for starting this up!)

[Berni]

Hmm interesting idea with wax. It is indeed well known for this property.

Lets crunch the numbers on that Wikipedia claims wax has about 200 J/g of latent heat. Converting back to the same units gets us 55 Wh/kg. This is a pretty impressive figure when you consider its simplicity and essentially infinite charge/discharge cycles. But its still only half as good as a Ni-MH battery while having the disadvantage that you can't concentrate all of the heat into the desired place like you can using electrical sources. This spread out heat source means more heat loss trough the same insulation.

There is another way to go about it. Increase the performance of the insulation instead. There are practical limits to how much insulation you can wrap around it before its a impractically large ball of fluff. However another insulation technology is a vacuum thermos, providing incredibly high amount of insulation without being physically large. This does add about 500g of weight due to the inside often being glass. But from some info online it appears a reasonable thermos will let 1 liter of 100°C water drop to 85°C over 5 hours in freezing ambient. So water has 4.2 J/g/K of heat capacity meaning the thermos lost 63 kJ of energy or about 12.6 kJ/h, this works out to 3.5W. Taking a more reasonable delta T of half that gets is to about 1.7W. So yeah keeping anything physically large warm is quite difficult. Tho having it fit inside a thermos might be a good form of secondary insulation to ease the work of the insulation around the hot reference (At the cost of significant extra shipping weight however).

[AG7CK]

Maybe we start separate thread on this? As where did you get 55ppm/K figure? I recently stress-tested LTZ1000A ref (chamber temp outside of oven setpoint) and got much smaller TC, around 3ppm/K. If the real swing would be near +/-155C that would mean LTZ die will be very much dead already.

I will get to it, but all my meters are currently busy characterizing FXes, need to get these shipped to EEVBlog members already, including members of EU Club. 

Hello Illya,

measurement technique and T.C. determination are here: https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg1336575/#msg1336575

That ~ +55ppm/K was also confirmed by other volt-nuts, but I can't find the link at the moment.

I doubt that you correctly measured these 3ppm/K.

Anyhow, something else happens in the 7000s cycling process, than only the change of the oven temperature. To find out, you really need to measure directly this Ube of the reference element. Maybe your 3ppm/K measurement was done at the Ube of the transistor of the oven control circuit, instead ?!

Frank

A TC of +50ppm or so has been mentioned many times on the forum. Even if I have never measured or seen published any value, there is a compelling reason to believe that it is a reasonable number.

In several Datron schematics there is a series resistor added on top of the LTZ avalanche diode. Typical value afaik is 21 ohm or so.

Suppose that the naked LTZ has output 7.0 volt and a TC of +50ppm. One degree temperature rise will then rise the ref output with 0.00035 volt.

Assume also that the temperature compensating Vbe of the LTZ1000 in-reference transistor falls with -0.002 volt, and finally assume that the current determining resistor (that is in parallel with the base-emitter diode of the above mentioned transistor) is the standard 120 ohm.

A one degree rise in temperature will then reduce the current in the avalanche diode
with -0.002volt/120ohm= -0.000166(6666....) ampere. This fall in current will give a fall in voltage over a 21 ohm resistor equal to -0.0001667amperex21ohm= -0.00035 volt or so (ignoring numeric rounding). This incremental voltage fall thus cancels the voltage rise from the supposed LTZ1000 TC of +50ppm.

Hence the addition of the resistor in the Datron LTZ1000 reference circuits strongly suggests that the raw TC is +50 or so ppm.

[AG7CK]

Maybe we start separate thread on this? As where did you get 55ppm/K figure? I recently stress-tested LTZ1000A ref (chamber temp outside of oven setpoint) and got much smaller TC, around 3ppm/K. If the real swing would be near +/-155C that would mean LTZ die will be very much dead already.

I will get to it, but all my meters are currently busy characterizing FXes, need to get these shipped to EEVBlog members already, including members of EU Club. 

A measured or calculated TC of +3ppm/K seems imo erroneous. Please document your findings.

[IanJ]

Hi all,

Forgive the ignorance but what is the EU - CalClub.........I saw the thread for the US one but have never followed it so not really sure whats going on.

Ian.

[Dr. Frank]

There ist a deeper solid state physics reason/law, why ALL the LTZ1000 chips have about this T.C.
Any silicon diode with CC has quite exactly -2mV/°C.
The T.C. of zener diodes is always around zero @ 6.2V zener voltage, like 1N821.
It is predictably more and more positive at higher zener voltages.

Fluke has chosen and specified a Reference Amplifier voltage, so that the sum of both T.C.s nearly cancel, and that is about 6.9 V. The LTFLU is explicitly specified, that T.C. can be trimmed to zero by slight change of collector current.
As the LTZ 1000 has a zener voltage of more than 7.0V, its sum T.C. is  definitely higher, and predictibly at these +55ppm/K @ the 7.118V, which I measured.
Therefore, for physics reasons, the 3ppm/K must be wrong, or TiN has got an LTZ1000 with about 6.9V reference voltage.

If LT creates a new version of the LTZ1000, they should change the diffusion for a 6.9V ref. voltage.

Frank


 

[hwj-d]

Hi all,

Forgive the ignorance but what is the EU - CalClub.........I saw the thread for the US one but have never followed it so not really sure whats going on.

Ian.

Hi Ian,
that's a legitimate question, because we've not yet defined this more precisely.

I'll start from the back. Shipping costs, and -handling (extra costs), customs duty, duration, stress to the Ref's makes it unwieldy to send them regularly abroad/overseas and back. So we want to do this within europe.

To help someone with a relative precise and (edit: ourself-) calibrated voltage and resistance standard as adjustment of its own measurement devices is the closer reason.

The ref's themselves should be continuously logged (ftp) and, depending on which hands they run through, also freshly rated.

[The Soulman]

Hi all,

Forgive the ignorance but what is the EU - CalClub.........I saw the thread for the US one but have never followed it so not really sure whats going on.

Ian.

Just a group of people that send out a artifact/reference to each other to be able to compare each other volts and ohms,
the usa cal club has one reference (ltz1000 and vishay vhp(?)) that is shipped from one member to the other.

The discussion here is to start something similar but different in the eu, suggested are multiple artifacts and shipped in star pattern.
So the artifact returns to its "home base" after each go, to check for drift and deviation etc.

What that artifact should be and should be capable of is now getting discussed here.

imho multiple small, light weight and robust references should be used and perhaps a small (flat) form factor so it can be shipped as a letter, cheaper and more convenient.
Also 10V and 10K Ohm should suffice, people should do their ratio's at home, or get a 3458a to do it for them. 

[YetAnotherTechie]

Hello,
I see you guys are considering shipping the references hot. Would a drop of 5º of the internal heater be acceptable? what about 10º? Sure it's not instantly settled at the destination, but knowing the audience, i figure people would leave it to settle for many hours/days, after receiving it.
Is there an amount of temperature drop whose drift that can be absorbed in the usual settling time at the destination? every degree less would save a considerable amount of power, and battery.

[bsdphk]

One note about shipping hot:  Remember that delivery vehicles can become very hot during summer:  Do not over insulate if the thermal regulation timeconstant is large.

[nnills]

There ist a deeper solid state physics reason/law, why ALL the LTZ1000 chips have about this T.C.
Any silicon diode with CC has quite exactly -2mV/°C.
The T.C. of zener diodes is always around zero @ 6.2V zener voltage, like 1N821.
It is predictably more and more positive at higher zener voltages.

Fluke has chosen and specified a Reference Amplifier voltage, so that the sum of both T.C.s nearly cancel, and that is about 6.9 V. The LTFLU is explicitly specified, that T.C. can be trimmed to zero by slight change of collector current.
As the LTZ 1000 has a zener voltage of more than 7.0V, its sum T.C. is  definitely higher, and predictibly at these +55ppm/K @ the 7.118V, which I measured.
Therefore, for physics reasons, the 3ppm/K must be wrong, or TiN has got an LTZ1000 with about 6.9V reference voltage.

If LT creates a new version of the LTZ1000, they should change the diffusion for a 6.9V ref. voltage.

Frank

If the vref = 6.9V the zener should be 6.2V(assuming a LTZ1000 circuit). If the zener has no tc. at 6.2V why put the transistor(diode) in series(again assuming a LTZ1000 circuit)? Would it not create a -2mv/K tc.?

[Dr. Frank]

If the vref = 6.9V the zener should be 6.2V(assuming a LTZ1000 circuit). If the zener has no tc. at 6.2V why put the transistor(diode) in series(again assuming a LTZ1000 circuit)? Would it not create a -2mv/K tc.?

Well, your assumptions are not correct.

At first, a silicon diode, or a Ube diode have about 0.5V forward voltage at small currents of 20..200µA where the LTFLU is specified, but at room temperature of 25°C only.
At the intended 45°C oven temperature, the forward voltage is about 0.45V only, so the zener must have about 6.45 V, which gives a pronounced positive T.C.

Don't forget, that these -2mv/K are related to a 14 times smaller voltage than the zener, and to simply calculate the necessary T.C. of latter, it still is +2mV/6.45V*K = +310ppm/K !!

So to re-formulate your wrongly derived last question, why not simply use an 1N821 type zener with small T.C.?

The manufacturing variations of these 1n821 series (or of any zener diodes), are very big, so you can only get low T.C. by selection, which range from +/- 100ppm/K for the 1N821 down to +/- 5ppm/K for the 1N829. The yield for near zero T.C. is extremely low..
In any case, you have no chance to trim the T.C. externally to exact zero. This is required for non-ovenized applications (The LTFLU is specified for 25..45°C application temperature.)

Therefore, you need such a Reference Amplifier, which can be trimmed to exact zero T.C. by variation of collector / Ube diode current @ 3mA zener current.

The other intention is to quite simply amplify the reference voltage to 10 or 15V, inside the different FLUKE reference applications.

Frank

[branadic]

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]

I pretty much appreciate tear down pictures. This unit is really interesting and with the upgraded battery pack with 1700mAh instead of 850mAh and thus 30h instead of previously 16h together with it's low power consumption <1W this is the perfect candidate by now for hot shipping. So Illya, you might want to put the teardown in the upper place of the priority list?
I'd also like to know more about the recovery methode, especially the details not covered by the patent or the paper. Would be great. A live stream on that is also welcome

-branadic-

[TiN]

My apologies for mixing up tempco of unheated LTZ zener vs out-of-oven margin LTZ tempco output. These are obviously not the same things. 

[FriedLogic]

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.

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.

You've been busy!

Have you ever tried cooling them down to a low temperature before each power up? That sort of temperature cycling is not ideal, but at least it would happen regularly and the starting point would be similar each time.

[The Soulman]

Before another endless discussion about ltz1000 circuitry and compensation starts..

What would the potential members of the EU calclub would like to see in terms of specs and features?

10V and 10K or more than that?
sub ppm/K tempco or do we keep our labs close to the 20 dgr. C mark?
Noise?
Size/weight, small box that could be mailed more frequently or big and heavy with integrated battery's to ship it "hot"?

[Berni]

Well i for one don't have any sort of air conditioning in the lab so its never 20°C. Especially when summer comes around and night time temperatures start to rise above 20.

As for the hot shipped reference i guess most of the argument for that was the drift after being frozen in winter. Perhaps do both and have people opt into the hot shipped or cold shipped mailing chain. Could perhaps give a bit of insight if hot shipping makes a diference when both compare again at home base. That is if it never hangs up in the mail somewhere and its batteries run dry.

[e61_phil]

Here in germany (and GB as well) is the standard cal temperature 23°C and not 20.

[BFX]

Please write me down to the list 
LTZ rulez 

[hwj-d]

Short conclusion after the Stuttgart summit regarding a concrete implementation of the EU-Calclub.

My request to include the EU-Calclub design and organisation question on the speaker's agenda in the short term was rejected for understandable reasons. It simply didn't fit in in terms of time and topic. Dr.Frank was kind enough to integrate the topic into his remarks by once again clarifying the tempco problem of shipping at winter temperature.

But that means nothing else than that we, as interested parties of an EU-Calclub, did not get any further with the organizational question and the reflection to a technically feasible variant as well as with the clarification of most different requirements to a reference than it was already addressed here in the forum anyway.

The question of preventing hypothermia does not only arise in this direction, however, if the possibility of overheating in summertime can be given on an equal footing. Preventing subcooling by means of polystyrene or other materials obviously does not work because it merely avoids emitting too much heat in too short a time, but not being able to heat passive elements additionally. And on the other hand we don't want to build perhaps
self-igniting paraffin-filled M...-Cocktails.

So my conclusion for the time being is that we have to get away from the idea within the EU Calclub of being able to build a highly qualified reference in our own rooms, but then also want to send it on its journey with this claim. For the same reason, it is likely more important to provide a higher quality reference to control a 5.5 - 6.5 digit DMM at the receiver, than to test the reference as an end in itself for the transmitter. Which doesn't rule out that the reference will be calibrated more and more precisely, depending on which qualified hands it passes through.

In my opinion, it is even completely irrelevant whether a "usage reference" as such(!) has suddenly migrated 5 ppm after the star-shaped control, if this is referenced accordingly in the cloud. Yes, it should even be expected that this will happen all the time!

I will probably first choose two of my LTZ1000 in a few days, and then send them to the first interested people under these conditions, in order to concretize our request further. In the end, it is of course up to each sender to decide under which circumstances he/she wants to make his/her references available.

I would like to thank every active participant, designer, sender or receiver, as well as all necessary constructive critics.

Regards,
H.-W.
 

[branadic]

My conclusion is:
A star comparison (send it to a receiver and back to the transmitter) is better then a ring comparison. This way you can see, if there was any change during transport. Furthermore the temperature of a LTZ1000 based reference should never fall below -15°C/-18°C.
Another point I extracted for myself is that the reference should be temperature compensated to zero t.c. by R9 and that reconstruction of the output voltage is possible as done in Wavetek/Metron/Fluke 7000 after a power down. Thus cool shipping of a reference with multiple styrofoam boxes stacked together should be possible.

-branadic-

[e61_phil]

Why not shipping hot? My LTZ1000 "Brotkasten" runs around 5 days from batteries.

Is shipping cost really an argument? It is still below 10€ even with heavy lead batteries and a protective case.

[dietert1]

At the metrology meeting Stuttgart i thought i wanted as transfer standard a 10 V reference with builtin microvoltmeter, so that the transfer is a direct comparison and independent of another reference in a high resolution DVM. A 12 Bit AD converter with a range of +/- 100 uV would be good enough for this.

This could be something like a MSP430 or Cortex M0 that runs on a small battery. At the same time i'd like to replace the analog thermostat of my AD587 reference by a digital one including temperature logger. The current analog implementation lacks monitoring during travel and voltage transfer. It stays "hot" for about a week on a usual USB power bank.

Then it's a minor step to implement a "freeze protection" mode where the thermostat is off and will turn on only to avoid temperatures below 0 °C. With this concept the whole device including the battery should travel safe for one or two days and the transfer should be much easier, too. So the standard returns faster.

Don't know when i will have time to work this out.

Regards, Dieter

[cat87]

I think within the western part of Europe,  sending the reference powered on is doable,  both in terms of shipping costs and time. Within the 5 days that e61_phil mentioned is doable. However,   for the eastern part,  I think it takes considerable longer than 5 days.

 On the other hand,  shipping the reference cold means that each recipient will have to have the same temp in the 'lab' as the one at calibration time....I personally can't do this and temperature deltas as high as 5 degrees are not uncommon.

All in all,  probably sacrificing resolution and low noise so that the reference is available to a larger part of members in Europe would be ideal...
Or maybe even have 2 references running around?  (one hot and another cold) so that each can pick and choose depending on the estimated travel time

[3roomlab]

just to add some data to the "shipping problem"
there are many articles about shipping temperature on/in US continent
I cant find much on/in EU
but this 1 article, not really EU but "japan to netherlands". the netherlands portion temp wiggle is not small.
https://interdry.wordpress.com/2012/01/27/ocean-container-temperature-and-humidity-study-2/
the span is nearly 40C. I think this could make permenent shifts in ppm (as observed by DrFrank in his findings)
not sure how they did the measurements, but looking at some US based transport papers, they also have similar wiggles.

middle of year


year end


this 1 is from some kind of wine transport log


I put this into LTspice, assume some thermal mass numbers which is approximately familiar. this is a 0 to 50C swing going thru box/VREF insulation stepping of 10 to 400 C/W. the timescale is 1:1.
insulation have some effect esp at 400C/W. but 400 C/W means (for a 5x5x5 cm box) something like 8inch of 0.035W/mk foam, item becomes an elephant! doubling the surface area of the box = double the thickness 16inch. size becomes a factor? maybe?
another rough simulated figure @ 400C/W approx saving in internal heated power is 4x, @ 200C/W saving in internal heated power is 2x. either a crap ton of insulation or crap ton of battery I suppose there is no escape from power of mother nature. (but these are all LTspice based numbers, and I think the temp ramp is too slow, should be nearer to trapezoidal square)
edit1 : I think if the shipping is long and far, the insulation could be thick. if the shipping is short and near, the battery could be heavy instead. but Im not sure

[Echo88]

Can you show us the Brotkasten?

[hwj-d]

I can't mention enough:

• We have more than one senders with more than one reference. For the very first beginning I spend two ltz1000 maybe my orange dekabox too.
• Others may have better Refs, bigger styropor packages, hot or cold ones.
  That all belongs to the senders convenience and expediency.
• The shipping pattern was star-shaped from the very beginning.
• It should announce itself senders, which can make now (this month) a ready reference available.
• Ideas, building plans, further ideas are of course welcome. Once they have been assembled and tested, they can also be securely integrated in the future, but we should concentrate on fully assembled references for the current project.
  What is available now?!
• The only condition is an online maintained list of the actually available references, their current state together with their whereabouts, and a current measurement protocol depending on the metrological capabilities of the receiver and transmitter.

My concluson (and proposal) is:
 do what you can do in the real moment, but
   keep it simple!

 

Thanks,
H.-W.

[wim.de.jong.59]

Please, put me also on the list to start with.

I've the following equipment:
Fluke 5450A
Fluke 732A, 2*
Fluke 731B, 2*
Fluke 742A 10K
Agilent 3458A
Agilent 34401A
Fluke 8505A
Fluke 510A, 1KHz

Maybe, its an idea to start with a Fluke 731B which is characterized for 20-25 C?

Wim.

[The Soulman]

Please, put me also on the list to start with.

I've the following equipment:
Fluke 5450A
Fluke 732A, 2*
Fluke 731B, 2*
Fluke 742A 10K
Agilent 3458A
Agilent 34401A
Fluke 8505A
Fluke 510A, 1KHz

Maybe, its an idea to start with a Fluke 731B which is characterized for 20-25 C?

Wim.

 

Welcome to the forum Wim,

Are you a hobbyist, or do you actual need all this gear? 

[Storm]

Please also put me on the list as well...

Cal Equipment:
Fluke 5440B (2x)
Fluke 5101A
Fluke 5200A (to be restored with one spare unit for parts)
Fluke 731A
Fluke 720A
Fluke 845AR
Fluke 845AB
Fluke 8502A
Fluke 8505A (2x)

Next project is a LTZ1000 REF-Standard to calibrate all of the above. I will use Dr. Frank PCB, new LTZ1000ACH and precision Resistors from Edwin Pettis. Still need to read a lot about this topic but the metrology virus already struck me hard...

I am a hobbyist but intend to use this equipment to restore and calibrate all my other stuff!

[Zucca]

As soon I got the 10V ref. Board form TiN, I would be happy to join the club with my other expensive toys.

[alex-sh]

Are we getting anywhere with EU Club?


Thanks
Alex

[Martin.M]

is the club only open for people who own expensive toys or also for some who have anything to check up?

Keithley Calibrator / Source 263  needs cal (Triax) so I will not offer to use it for anything..

I have a Fluke 883A what is a full year ago gone to a friend from fluke germany, but I think he will not find time to cal + adjust my oldie, so 883A needs a cal / adjust also.

Here is a restorated Tek 213, the intern multimeter is to cal 

Also a restorated Fluke 8500A DMM, to cal

.. and some other oldies .. on the makerfaire Hannover it was not possible bec. the cal place from the PTB was always busy.

Martin

[dl2ocb]

Hello to all Voltnuts,

a little nice CalClub would be fine.

I got some gear that should be compared to get better Feeling about Stability and Accuracy.

GenRad 1440 10kOhm and 100kOhm last Cal in 1968
2x LTZ1000 7V KX References (build 08/2019)
2x Fluke 720a KVD
2x HP3457a DMM
Russian Decade Resistor

I would be happy to contribute with Measurements in RF Domain (partly to 40 GHz). (https://dl2ocb.de)

Hope to meet some of you in Kassel to the DARC Funk.Tag 2020, im there rocking the Funkmessplatz (https://funkmessplatz.info)


CU
Stefan

[branadic]

After one year of the initial idea to the EU or at least DE cal club, how are things going?
Unfortunately Metrology Meeting 2020 had to be canceled, so chances are gone to compare to Michels Metron/Wavetek 7000 (M69) and even more, I didn't had the chance of comparing references to M71, that had been circulating last year and also showed up on Maker Fair

So since I have a few things that I would like to compare to some well known 10.xxxxxV reference, I'd like to ask: who can contribute something to a star case cross comparison? Current temperatures outside are good and in case we are still concerned about temperature with power off, I'm sure I will find some proper styrofoam box at work.

If noone has a proper reference, I can contribute a temperature compensated LTZ 7.xV with AC wall adapter and cable for lab power supply. I can measure it against our 3458A and K2002 but also my R6581D and S7081 prior shipping. By star case comparison and reporting the measured value to all contributors, we can recalculate our own readings. Maybe we find some contributors with calibrated gear and cal reports, that could be added each time the reference is shipped further?

Awaiting your response and hoping, that it won't take another 120 days or year to get something up circulating.

-branadic-

[The Soulman]

I can put together something small with a selected (1ppm/dgr c) LT1021dmh-10 and a non-characterized 10KOhm
ESI wirewound resistor, that could and should be done after assembly, also the LT1021 needs multiple thermal cycles after
soldering to make sure it has not shifted or is prone to shifting.
After that at least two weeks of monitoring, also can not give a reading to any meaningful calibration uncertainty, I'd
like to think I'm in the 10ppm ballpark, but more likely 40ppm or so.
So preferably first receiver should put more accurate numbers on it.

If anybody sees use for such let me know and I put it together, although already I'm aware it may not please the 3458/732 crowd.

[Dr. Frank]

Hello André,

as always, I offer my transportable LTZ and a 10k references, aligned during last Metrology Meeting (1y.) and to M71 (1/2 year ago). Plus a better attempt for drift prediction. Plus styrofaom box to transfer them safely.

I am currently updating LTZ #5 on battery operation, i.e. AnJa's design. Very stable reference, still, after all that Change stress.
Doubt that it can be sent via DHL, due to mechanical constraints. Wonder if AnJa ever shipped any of his references.

I'd prefer a small scale volt-nuts meeting in Stuttgart region, instead.
I've got time, working in Home Office, and I would contribute local Äppelwoi, and Handkäs with music, if not declined.

Frank

Edit: There's really an English Wiki: https://en.wikipedia.org/wiki/Handk%C3%A4se

[branadic]

Hello Frank,

the idea of a small scale meeting is very much appreciated. 

Unfortunately the battery don't last long enough to ship the references based on Andreas's design, as shiping is somewhat unpredictable in time, but it is a good reference for personal transport.

-branadic-

[Andreas]

Hello,

I already thought of a power bank (there are versions up to 50000 mAh available) and a small step up regulator like in my AD587LW reference to buffer the internal batteries during land based transport.

with best regards

Andreas

[MiDi]

Is there any information on how much hysteresis can be expected from LTZ1000A (e.g. setpoint ~50°C (12.5k/1k)) when switched off several days (room temp ~21°C)?
If this is negligible, would it be feasible to add an efficient circuit to power only the heater and maintain e.g. min 21°C inside LTZ to achieve significant lower power draw for shipment [at low temperatures] and get rid of significant hysteresis?

Problem with powerbanks is that there are restrictions for shipment, in particular if they are switched on.
If I remember correctly all Li based cells are problematic, but lead acid, NiCd, NiMH do not have significant restrictions - even when delivering power.

[mendip_discovery]

Here in germany (and GB as well) is the standard cal temperature 23°C and not 20.

This is general aim for calibration labs in the UK (UKAS etc).
Mech Labs it is 20°C ±2°C
Electrical Labs it is 22°C ±2°C

The difference I am lead to believe is because of the US manufacturer of meters and a preference for slightly warmer conditions.
The closer your temp is to 20 or 22 can help reduce your uncertinty.

[MiDi]

Thanks to Dr. Frank I got a 10kΩ and 7V Reference to compare against my ancient HP3458A and to do a transfer to my references.
I have essentially no experience with these kinds of calculations, please forbear with and correct me if I made a mistake.

The specs of HPAK 3458A and the given uncertainties of the references from Dr. Frank are expected with an extended measurement uncertainty (k=2).
For the reference values I used the mean values provided by Dr. Frank before and after return and added half of that drift to the uncertainty:

LTZ #2 (powered from delivered wall-wart):
7.118223V + 0.5ppm/2 = 7.118 224 8V
EMU: 2ppm + 0.5ppm/2 = 2.25ppm

My results (Mean from 16 measurements with 100NPLC, AZ ON):

7V:	7.118 241 0
-7V:	-7.118 237 3
Offset:	1.52µV
StDev (7V):	206nV
7V offset corrected:	7.118 239 4
-7V offset corrected:	-7.118 238 8
Value Offset corrected:	7.118 239 1
T-EMF & INL 3458A:	320nV -> ~0.05ppm of measurement
ppm diff:	2.0

Result 10V range: +2ppm +-2.25ppm

V336 10k:
9999.979Ω - 1.4ppm  + 0.5ppm/2 = 9999.968Ω (-1.4ppm is extrapolated drift from last cal by Dr. Frank)
EMU: 3ppm + 0.5ppm/2 = 3.25ppm

My results (Mean from 6439 measurements ~15h, APER 1, DELAY 1, OCOMP ON, AZ ON):

10k:	9999.963Ω
StDev:	0.28ppm (Mean of moving average from 16 measurements)
ppm diff:	-0.4

Result 10kΩ range: -0.4ppm +-3.25ppm

I am impressed by the results - they are much better than I expected.
The drift in last 4 years compared to 2016 are in the order of +1ppm/year for 10V and -1ppm/year for 10kΩ range.

The T-EMF & INL of 320nV are around 0.05ppm of measurement (7V), that is in the order of the spec for INL of 3458A.

Attached the results from last cal of pre-owner 2016, from Maker Faire 2019 and last but not least current results from 2020.

[branadic]

Hi MiDi,

I noticed, that it seems your Guard is set "To LO" instead of "OPEN" on 3458A, while Guard is not connected to LO at the reference. Because of that we had quite some shifts during MM2020mini that were reproducable afterwards.
Has Frank measured the reference the same way you did, I mean the same wiring scheme?

Edit: I'm also curious about your uncertainty values, they seem a bit low. For comparison, Keysight Böblingen gives +/-2.5ppm on our 3458A calibration. Why you add only 0.5ppm/2 to your uncertainty? Maybe you can elaborate on that numbers?

-branadic-

[MiDi]

I noticed, that it seems your Guard is set "To LO" instead of "OPEN" on 3458A, while Guard is not connected to LO at the reference. Because of that we had quite some shifts during MM2020mini that were reproducable afterwards.
Has Frank measured the reference the same way you did, I mean the same wiring scheme?

I followed 2ppm hunt in MM thread 
The measurement for LTZ#2 was taken as shown on picture, Guard closed and connected to case of LTZ#2.
I have done comparisons between all possible configurations for guard open/closed and guard connected to case or to low on LTZ#2.
Afair there was no significant difference in the readings, unfortunatly I lost the notes, so nothing left as foundation 

Edit: I'm also curious about your uncertainty values, they seem a bit low. For comparison, Keysight Böblingen gives +/-2.5ppm on our 3458A calibration. Why you add only 0.5ppm/2 to your uncertainty? Maybe you can elaborate on that numbers?

For the reference values I used the mean values provided by Dr. Frank before and after return and added half of that drift to the uncertainty:

There is no added uncertainty for my measurements, I just used uncertainty Dr. Frank gave for his references.
After return, Dr. Frank told me that both references drifted by ~+0.5ppm.
As I said, I have no experience with this kind of calculations, if this is wrong, please push me on the right path.

[branadic]

Progress on EU Cal Club kit.
I finished my LTZ1000#9, it's tc compensated and the output adjusted. I measured:

10.0000537V (+5.4 ppm) over 16 values (~1 min) with a standard deviation of 366 nV and 10.0000535 V with a standard deviation of 360 nV over 781 values (~52 min), measurement taken with 100NPLC or 4s integration time with R6581D

The reference has been with Frank and he confirmed the results with his 3458A:

10.0000508 V (+5.1 ppm) with a standard deviation of 224 nV over 10 min, 302 nV over 1 h and 587 nV over 18 h

A hardcase with foam inlay has been ordered, to make it a kit. Unfortunately I didn't had the time yet to also set up a 10k resistance reference, which should have been part of the kit as well, but I'm working on it.

-branadic-

[Andreas]

Hello branadic,

do you plan to put a temperature data logger into the case?
E.g. something like this?

https://www.amazon.de/Temperatur-Luftfeuchtigkeits-Datenlogger-Rekorder-Digitaler-Temperatur-Datenlogger-Rekorder-Lebensmitteln/dp/B083JSL3DM/ref=sr_1_2_sspa?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=3DBNEWBS4WZL3&dchild=1&keywords=elitech+rc-5&qid=1604773291&sprefix=elitech%2Caps%2C178&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExV1lNRDlESlo3V1VYJmVuY3J5cHRlZElkPUEwMDY3OTI2MzFQT0YxMDRIRTc2SSZlbmNyeXB0ZWRBZElkPUEwMzA4NTc2M0RERjczR1JQTkMxJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==


with best regards

Andreas

[Dr. Frank]

As promised, I'd offer one of my monitored 10k, VHP202Z resistors, with operational description.
Frank

[branadic]

Andreas,

a logger would be nice, agree, but I don't have one yet and boycott to buy from Amazon

-branadic-

[Sprock]

Hello Branadic

if one could have access to a PT100 or NTC 10k from outside.
Lemo B (Reichelt: EGGOB302CLL -2pol) or similar if place is there.
Just a idea.

best regards
Sprock

[Dr. Frank]

At least a temperature data logger is urgently required during transport!

Our 'secret' volt-nuts club uses a similar to AZ Corp. (Taiwan) 88163 AZ (T+ humid. + Press.) pdf logger inside the suit case.
That's especially important, as both non-heated references (V, R) will show a hysteresis of several ppm if they are exposed to temperatures below about 0°C.
Temperatures below -15°C might literally harm the LTZ1000 stability.

Transport should only be done, if environmental temperature is > 10°C, to be sure.  I have not seen any hysteresis on both, down to this temperature.

My VHP202Z reference assembly contains a precision NTC, which is sufficient to reproduce its T.C. behavior, and to calculate its correct resistance value at the given environmental temperature.

Andrés LTZ #9 reference is temperature compensated to a level being irrelevant to volt-nuts level comparisons, i.e. on the order of a tenth of ppm over +/- 10°C, or so. André for sure will specify that precisely.   

Frank

[Andreas]

Hello,

for a similar price I found the UT330C Humidity/Temperature/Pressure Datalogger @ Reichelt.
https://www.reichelt.de/datenlogger-temperatur-luftfeuchte-luftdruck-ut-330c-p147784.html?&nbc=1

with best regards

Andreas

[branadic]

Thanks for that hint Andreas, bought a used unit cheap, that already arrived today.

-branadic-

[branadic]

A test run on German ring comparison with LM399-PWM-DAC started today, final measurements happened yesterday, today the small pelican case clone with the reference, a linear wall adapter, cable for the internal temperature sensor (10k NTC) and UT330C ambient datalogger made its way to first participant.

"Each journey starts with a very first step."

-branadic-

[branadic]

So we have finished our test run and the results were already presented at yesterdays MM2022, here they are. Different to what was shown yesterday an additional and final measurement point was included.
Some lesson were learned and can help to improve future CAL runs within Germany or even EU.

Thanks to all the 13 participants that used the very short time very effective.

-branadic-

[Andreas]

Hello,

and the best of all:
there is virtually no change of the LM399-based 10V reference during transport if you compare the first Measurement (#1) with the last (#18) with the same instrument.

So it is a big success.
Thanks @branadic for organisation.

with best regards

Andreas