DMM Volts/Ohm Calibration Club - anyone interested?

[enut11]

SEE CHANGE OF SCOPE REPLY #28

I have a HP3456A which is un-calibrated but still nice to use for many hobby metrology projects or for just learning about small signal measurements. It would be nice if it were calibrated at minimum and adjusted at best. However, I am not about to spend $2000 (or whatever) to have it tested and adjusted but I might consider spending ~$200 if I had access to a known stable voltage and resistance standard.

Proposal:
Who would be interested in being part of a Calibration Club? The idea is that 10 people pool an amount of money sufficient to calibrate and adjust one of the members' high end DMM (say a HP 3458A). In exchange, that member would make available by post a voltage standard and a resistor standard checked against his 'reference meter', to the other Club members.

Once a Club member has checked his own DMM he then returns the volt/ohm standards to the reference member who would then re-check the standards ready to ship to other Club members.

Could something like this really work?
What voltage/resistance standards would be required to satisfy potential members?
What are the pitfalls?
Would the outcome be better than no calibration (current situation for many)?
What would YOU pay to have more confidence in your 5-8 digit DMM?
enut11

[JS]

  I like the idea, while is no use for me right now and I don't think I could join from here. That could start an extraoficial network of traceability, without the liabilities or the cost but without the paper work either. Maybe it gets a day which becomes a GNU version of the standards... 

JS

[TiN]

What voltage/resistance standards would be required to satisfy potential members?

1. Characterized 10V standard based of LM399 for DCV (over 20-40C ambient temp, over 12-20VDC input)
2. Characterized 10K standard based on hermetic foil or wirewound resistor for OHM (over 20-40C ambient temp, over 1-10mA current)
3. Perhaps 1mA current source based of same LM399 as self-check point
However this would not help to calibrate most of the meters other than 3458A, so it's rather only for base range check.

What are the pitfalls?

Few : Shipping cost. Module can be made small, but still would be 40-80$ to ship internationally.
Risk of loosing the package. Also frequent shipping back is required to make sure reference still agree to original values.

Would the outcome be better than no calibration (current situation for many)?

If one after absolute accuracy - yes, of course it would be better.
If just need ratio measurements - not so much.
But perhaps it's less useful for more popular 6.5-digit DMM owners, because even for simple check you need 1V,10V,100V,1kV/10ohm-1Meg in decades, not just 10V/10KOhm.

The idea is that 10 people pool an amount of money sufficient to calibrate and adjust one of the members' high end DMM (say a HP 3458A)

I'd skip on this idea, and modify it into "few members that already own calibrated reference meter help to check travelling reference box". Not much would like to pay for calibration of someone's meter with unknown outcome, as this "club program" would be a long-term thing, not a "all done in one month".

I can jump in and help, but will need exact and defines conditions of such activity to be ran, so it would be helpful.
Ideally I can see this as next path:

A. Design and build few pieces of "Travel-box" with DCV,OHM reference in it and perhaps Raspberry Pi Zero with EEPROM to store measurement data/temperature/environment condition and test member name.
B. Send it to well-known volt-nut "A" to calibrate for DCV,OHM reference value over temperature range
C. Assign measured data to box
D. Send it to club members "A" -> "B" -> "C" -> "D" -> "E" -> "F". Set hold time e.g. 2 weeks for each member, so it would take 5 months for 5 members to loop a reference (2 wks shipping, 2 wks test)
E. Last member "F" sends unit back to "A" to recheck and recalibrate if required. Deviation and delta of each member data would be recorded
F. Repeat cycle again.

[enut11]

Thanks for the comprehensive feedback TiN. I like the all-in-one roving standard. Several voltages and resistances would be ideal as well as a current standard. Perhaps a pool of money to fund this box is in order. I do not have the skills (yet) to build a 'metrology' grade reference unit.
To reduce travel time and cost, each country could have its own calibration club? I live in Australia. enut11

[2N3055]

Sounds interesting.. Subscribed...

[Dr. Frank]

In metrology community, such Key Comparisons with Travelling Standards like 10V zeners, 10kOhm, ratio divider and AC/DC convertrers, are very common.

This is useful for participants, who would afterwards be able to transfer at least 10V and 10kOhm to all other ranges and modes of their DMMs, i.e. who have appropriate transfer standards available in their own labs, requiring a 3458A, or calibrators like the Fluke 57x0A.

Otherwise, the bare exchange of 10V or 10kOhm will not really calibrate DMMs, as these usually need about 35 different artefact values.
The "check" of the say 10V and 10kOhm range of your DMM also has absolutely nothing to do with "calibration".
That's why I regard these DMMCheckers and alike as being quite worthless.

So yes, that idea is nice, but this will have a different scope than the title implies.

Here in Germany, we already have quite some exchanges of artefacts, instruments, or better, we sometimes meet at some volt-nuts homes to do elaborate comparisons or calibrations.

Frank

[enut11]

Thank you Dr Frank. How this evolves, and I hope it does, will depend on what the members want. For myself, I'm after more confidence in what my DMM is telling me without spending a large amount of money. I am open to suggestions on how to go about it. enut11

[VintageNut]

I am interested as well.

I can some checks now and am in process of building a divider to transfer voltages.

I  have a calibrated KE2000 and I borrow calibrated gear on a regular basis. Recently I have been working on learning how to construct and measure a divider. I use a DMM7510 which for resistance between 10 ohms and 1 M is 27ppm to 35 ppm. 10VDC is 15.2 ppm.

As good as the DMM7510 is, its obviously better to have a 10V standard that is known to better than the DMM uncertainty.

To be serious about this, temperature has to be known. Should there be a uniform device to measure temperature for all of the participants?

There should also be standard practices for cables and measurement techniques. My cables are not great now. I can see the offsets from moving connectors.

[Theboel]

I do not know what the story in other parts of the world.
but here in Indonesia I think I am lucky about calibration (depend with Your point of view) for calibrated voltage standard (10v), Resistor standar (cardinal value), Frequency standard (10Mhz).
I can calibrate it in our NMI (KIM-LIPI) against their standard traceable to BPIM with minimum of money (150USD to 200USD) and because I am the only person in my country have ask to calibrate my standard to national standard they give me extra effort for me.
1. I do not need to wait up to 6 month like their company customer.
2. They help me to do regular calibrated (in my case every 90 days) so I can made a history about my standard.
all this thing may be a very special case in my country but I think no need to shame to ask Your NMI about what service they can do for You. I already talked to 2 foreign NMI basically they surprised when I tell them who I am and why I need their services and their very helpful about my question but they suggest me to talked to my NMI first before use their service.

[Alex Nikitin]

For a while now I am thinking about a portable DC only "calibrator" with the following values available : 1V, 10V, 100 V (up to 1mA max output so it is safe) , 10mA, 100mA, 1 A (up to 1V max output), 1K, 10K, 100K, 1M . It should work from an easily available supply (say, a 5V USB adapter or an external battery pack with a USB connector) so you don't need to worry about power arrangements, <10ppm accuracy on voltage, <20ppm on resistance and <50 to 100ppm on current ranges. A fairly small size (1x2x4'')Captive 5-way leads with low thermal emf banana plugs, so it could be just plugged in. This kind of a unit can be easily posted by a recorded small packet post. Does it look like a good idea?

Cheers

Alex

[2N3055]

For a while now I am thinking about a portable DC only "calibrator" with the following values available : 1V, 10V, 100 V (up to 1mA max output so it is safe) , 10mA, 100mA, 1 A (up to 1V max output), 1K, 10K, 100K, 1M . It should work from an easily available supply (say, a 5V USB adapter or an external battery pack with a USB connector) so you don't need to worry about power arrangements, <10ppm accuracy on voltage, <20ppm on resistance and <50 to 100ppm on current ranges. A fairly small size (1x2x4'')Captive 5-way leads with low thermal emf banana plugs, so it could be just plugged in. This kind of a unit can be easily posted by a recorded small packet post. Does it look like a good idea?

Cheers

Alex

That sounds like a fantastic idea..  I think ideal would be to have one that travels and also to have one of my own in the lab permanently..... I would be interested..

[2N3055]

The idea is to ship voltage reference.. LM399 voltage refs have very low thermal hysteresis, and do not drift when off.. The rest of the circuit is not so stable though..
Many people send their equipment via packet to get calibrated...
For me it wouldn't be so much a source of high end Voltnut quality reference voltage, but something I would use as a double check to check my voltmeters... To characterise at least partially meter's reference drift and to know when to send meter for cal+adjustment...

[HighVoltage]

I have several Geller Labs 10V references and could make one available for this purpose.
It would actually be interesting to see a change in the reference a few weeks later, after
it has traveled through some very cold places and airplanes.

My reference equipment would be an Agilent 3458A, a Keysight 34470A and a Keithley DMM7510
I could set the Geller Labs reference as close as possible to 10V and keep it running for 24h before sending it out.
I would also enclose a printout of the values measured buy the various instruments.

[enut11]

Thanks. Some great suggestions and ideas are being posted. Some of you have already built your own calibrators. Would you mind sharing a link to the description and construction in this thread?

I definately want more than a simple DMM checker - looking at those LSDs!

A hard blow moulded plastic foam lined case should survive the rigors of the postal and shipping services and protect the delicate calibration gear.

Nice as it would be to participate in an International Club, it may only work within a country if what DiligentMinds says is true of customs problems.

[retrolefty]

I've never come to terms of the 'calibration' Vs 'adjustment' definition.

 I would think what is being proposed here is just the sharing of a specific value voltage and resistance standard, they are calibration sources only if used to make adjustments such that when 'adjusted' the meter DUT readings match the published measurements of the shipped references? Otherwise it's just some kind of forum scoreboard if users wish to share their DUT readings for comparison?
 
 Are these two simple references all one needs to 'adjust' one's specific DMM, probably not?
I have no problem considering this proposal as a 'calibration validation program', but to consider and call it some kind of 'calibration program' still seems wrong to me.

 

[2N3055]

Well, as someone more knowledgeable than me explained, in metrology circles term "calibration" is actually measurement of your instrument in comparison to standard and documenting data..
A "check of calibration" would be more appropriate term..
In layman terms they give you table of how much your instrument is in error... To actually make your instrument accurate they call it adjustment or even repair sometimes, because if a component drifted out of adjustment range it needs to be replaced before it can be adjusted... Some labs do check and automatically adjust instrument if it is out of it's specified range, if you have such an agreement with them..
Many companies have such contracts with calibration places, so most of us equate "calibration" with "check of calibration and adjust or repair if necessary to make it accurate" because we wouldn't  worry about it.. You would give it to the instrumentation guys to take care of it..

So that is how it was explained to me..

[2N3055]

To explain my rationale: I have one good 6 1/2 meter still in cal...
I don't have 2 or 3 good meters like some other people here and frankly I don't think I can justify getting them..
But I could have one (or three) decent LM399 based references, and I think that would give me some certainty that I have something to check upon..
When my meter drifts enough as evidenced by those references ( and they agree) I will send meter for cal...

When it comes back I would start monitoring again...

I would be happy with just 10V for beginning and I would mainly like to check upon meter's reference drift. 

I'm not expert, can someone explain me how much of instrument drift comes from reference itself (for instance LM399 in RIGOL DM3068) and how much from other sources (dividers etc)

Best regards,
Sinisa

[enut11]

OK, if all you want is just a "DMM Check Standard" that provides some known artifacts for the meter to measure, then that is possible.  The price for this depends on how accurate you want these check standards to be.  You might be able to get away with some PWW or epoxy-packaged foil resistors (or maybe even good quality metal-film), an LM399A based voltage reference, and DCI, ACV, and ACI derived from that.  Maybe we can price the resistors (up to 1M\$\Omega\$) from Edwin, and then use whatever we can find for the rest.

What voltage(s) and/or current(s) and/or resistance(s) would everyone want?

1) The very minimum that I would want is a calibrated 10v DC and 10k that is within the performance tolerance of my HP 3456A, taking into account any temperature difference when these standards were calibrated.

2) Beyond that, it would be better if 1v were also available along with 1k and 100k

3) Wish list, but not necessary, would be also 100mV and 100v along with 100r and 1mohm and a current standard.
enut11

[TiN]

I'd start with very detailed and realistic (not like 5V USB-powered 100V 10ppm source specification for such travel-box.
To mitigate customs/shipping damage issues it should be priced relatively low (300-400$USD tops?) so loosing a box would not be end of the world.
This rules out expensive options, like using LTZ1000, hermetic 0.005% foil resistors and such, as just parts alone for these would overwhelm project cost by a lot.

Few months ago I actually did something which this thread imply (sorta), sent my one of my 2002s via post, and took second 2002, all LTZs and resistors std's with me on airplane to perform a calibration against fresh calibrated standards. It took a week of ~14 hour/day work to get just two 2002's and LTZ modules/chips (7pcs) calibrated, and that's not including ACV/ACI at all.
Then I took both 2002's and references back to my homelab, crosschecked them and confirmed that DCV still agree within ~2ppm on both meters and LTZ modules (unless all of them drifted same way from transport shocks, which is unlikely) and within ~8ppm for resistance. This allowed me to adjust 3458A to these absolute accuracy levels, and I could do third round of checks on references using 3458A (which stayed home and ran 24/7).

Of course there was some amount of luck that 2002's did not get smashed and destroyed or lost, and similar stuff. So I'd rather call this extreme way to calibrate homelab gear.
Again, if I did not have 3458A (which can calibrate from 10V/10KR), usefulness of such experiment would be much much less, as most 6.5-digit DMMs require proper MFC with many points to calibrate, so whole thing would boil down to check few voltages only.

I can help on hardware design for such a project and testing if community desire, but I'd prefer not to do it all myself at this point, as I have few other homelab projects to finish up first.

[Nuno_pt]

I'm with Diligent Minds on the problem that can be shipping International because of customs, in EEC there is no problem but if it's going/arrive from US or Asia that could be a problem, because it could be retain in customs almost 2 months, and one would have to pay custom tax plus 23% VAT, but if this project would go forward I'll ask the customs if there can be an exception for the product stay here for 2 weeks period, and share the replay here.

In my understanding we've to agree on some DCV and Ohm values, then agree on components, someone designing the PCB's for the DCV, order the PCB, assemble everything and then initiate the traveling for the box, preferable all in one box kind of thing.

The person(s) that is going to do the measurements should have the DMMs calibrate, if not the readings will/can be wrong, so would it be better if we could arrange first a network of unofficially adjust the DMM, some of the guys here have the proper equipment to adjust 6.5 digits DMM, if they will be willing to do that it's another story, but as an example, shipping one of my DMM (K2000 or 3457a) to anywhere in EEC would be between 30€ to 50€, that way I could have the DMM calibrate, and could do the checking properly.

For logging the parameters we could use an Rpi and BME280, the BME280 will log Temp, Pressure and Humidity.

[Alex Nikitin]

I'd start with very detailed and realistic (not like 5V USB-powered 100V 10ppm source specification for such travel-box.

That is not a very difficult bit. 10ppm accuracy and 90 days stability for 10V is do-able even without a heated reference, using, say, LT1021-10 in a metal can + LM35 to measure the reference temperature, and to scale it up to 100V with a self-calibrating Hamon divider can be accurate to <1ppm short-term. For me a difficult bit would be the current up to 1A with a reasonable stability from 500mA 5V available from USB supply  . I took the requirements for a full DC calibration of K2000/K2015 as that is what I have here and it would be nice to be able to check these easily. For the voltage only I can do a travelling reference fairly soon and test it for tempco and hysteresis.

Cheers

Alex

[TiN]

I'd avoid USB-powered anything for precision analog stuff to begin with. Same goes to battery, as postal services usually don't allow battery stuff for shipping. After Note7 shenanigans I'd expect rules to harden even more.

[Alex Nikitin]

I'd avoid USB-powered anything for precision analog stuff to begin with. Same goes to battery, as postal services usually don't allow battery stuff for shipping. After Note7 shenanigans I'd expect rules to harden even more.

No battery or power supply to send - that is the point. 5V from a USB charger/supply or a battery pack (sourced locally) is easily and cheaply available. An isolated DC/DC converter to provide regulated +15 and +110V for the reference and outputs, with a good isolation so the polarity can be swapped easily. As the power consumption is low, a simple (and cheap) low noise resonant converter will do the job (even if LM399 is used as a reference). 

Cheers

Alex

P.S. - with the LM399 it would be also possible to provide a direct reference output and anybody with a good linearity 6.5 + digits meter will be able to check 7v to 10V conversion ratio, to verify the 10V value, so the uncertainty will be reduced down to the reference drift and the linearity error for 10V, plus Hamon divider error for 100V. All resistive dividers errors could be controlled that way. A little bit more involved but a good cross-check for a travelling reference.

[2N3055]

I personally have no problem providing 24 V for the box.. for 100V would  still would need upconverter...

[enut11]

I searched www.eBay.com for "0.005% resistors" and got the following hits. Would any of these be suitable for this project?



1x Z204 100K000 0.005% Vishay Z-Foil Series Metal Foil Resistors Y1441100K000V0L
http://www.ebay.com/itm/1x-Z204-100K000-0-005-Vishay-Z-Foil-Series-Metal-Foil-Resistors-Y1441100K000V0L-/111862808308?hash=item1a0b8afef4:g:CCEAAOSwX~dWhNkB

NYT ULTRA PRECISION RESISTOR ARRAY 3PCS 10K OHM 4PCS 100K OHM 0.005% P444A
http://www.ebay.com/itm/NYT-ULTRA-PRECISION-RESISTOR-ARRAY-3PCS-10K-OHM-4PCS-100K-OHM-0-005-P444A-/401193617684?hash=item5d6900c914:g:4TwAAOSwOyJX4~h3

1X 10K/1K111111 0.005% VISHAY Precision Voltage Divider Resistor Metal Foil seal
http://www.ebay.com/itm/1X-10K-1K111111-0-005-VISHAY-Precision-Voltage-Divider-Resistor-Metal-Foil-seal-/111726922486?hash=item1a03718af6:g:oukAAOSwMmBVs8Dz

[enut11]

Based on the posted responses so far, the original idea to fund the calibration of a member's high end DMM and use this to calibrate roving standards did not get enough support.

Change of Scope
1) Most like the idea of a roving calibration system and maintaining a log to compare various members gear.
2) An accurate voltage and resistance standard to be built using best practices of eevblog forum members.
3) Members are divided on whether the roving standard(s) should be limited to a country or region to simplify customs and shipping.
4) System supply voltage be based on a local 18-24v supply.
5) Shipping container to be ruggard and protect delicate stadards, eg blow moulded case with foam cut outs.
6) Characterised resistors of 100r, 1k, 10k, 100k and 1m
7) Characterised voltage standard based on LM399 to provide unamplified output (7v?) as well as 1v and 10v.

So, we need a source of parts and someone with metrology experience to build the cal standard.

Also useful would be a headcount of those interested in participating as well as country of residence.
enut11 (Australia)

[TiN]

Hold on sourcing parts 

Few important parts are missed:

* Integrated captive cabling to external DUTs. E.g. Box should have shielded teflon insulated cable (L=1-2m) to have same connection to terminals. Good luck finding copper banana plugs for decent price (perhaps somebody with access to CNC/lathe could roll own ones?)
* Integrated environment condition sensing. Raspberry Pi Zero + BME280? That will need separate 5Vin jack for supply. Pi has to log data to SD everytime it's powered on. Let's say once a minute.
* Software support. Many of nuts may not be happy to poke buttons on DUT all day long to measure the box. So has to be automated. Best case: plonk USB GPIB to Pi, enter "/run_test" command and job done hour later. Further improvement: have switching function for functions in the box, so once wiring connected to DMM 4W port - it takes care of all DCV/DCI/OHMs automatically. Big iceberg hidden here, as DUT libs need to be written for each different DMM Vendor/Model.
* Budget - calculate estimated project cost. I'd expect this will reduce amount of participants 10 fold... Ballpark figures - resistors 20$/each, LM399 ref - 50$ (total), 7V-10V-1V (50$), Pi+BME (40$).

[2N3055]

Hold on sourcing parts 

Few important parts are missed:

* Integrated captive cabling to external DUTs. E.g. Box should have shielded teflon insulated cable (L=1-2m) to have same connection to terminals. Good luck finding copper banana plugs for decent price (perhaps somebody with access to CNC/lathe could roll own ones?)
* Integrated environment condition sensing. Raspberry Pi Zero + BME280? That will need separate 5Vin jack for supply. Pi has to log data to SD everytime it's powered on. Let's say once a minute.
* Software support. Many of nuts may not be happy to poke buttons on DUT all day long to measure the box. So has to be automated. Best case: plonk USB GPIB to Pi, enter "/run_test" command and job done hour later. Further improvement: have switching function for functions in the box, so once wiring connected to DMM 4W port - it takes care of all DCV/DCI/OHMs automatically. Big iceberg hidden here, as DUT libs need to be written for each different DMM Vendor/Model.
* Budget - calculate estimated project cost. I'd expect this will reduce amount of participants 10 fold... Ballpark figures - resistors 20$/each, LM399 ref - 50$ (total), 7V-10V-1V (50$), Pi+BME (40$).

As for head count, Croatia  (EU)

I would suggest serial (rs232, can easily be made optically isolated ) on RefBox  port and Python script on a PC side.. Simple enough to fix and poke around, works on windows and *nix-es.  I connect everything with Ethernet, USB and serial..

So RefBox would have it's own commands to read and write and all  the custom stuff everybody does in their own lab. Of course, we would help each other with the setup..
For example, someone poste DP832 + Keithley DMM calibration script, took me 2 hours to make it work for DP831 +DM3068..

In that case we could even drop an Atmega on board no need for Pi...

Thoughts?


Sinisa

[e61_phil]

I don't like the idea having such digital stuff next to some precision analog stuff.

Do you really need an automatic DIY multifunction calibrator for this purpose? I think having a box of artifacts is more useful. Therefore, everyone is able to compare the single resistors against each other and is also able to build known dividers and so on. Furthermore, connecting five resitors to the DMM isn't that time consuming, I think.

All these digital stuff, relais and switches will just increase the uncertainty of the stuff and a defective artifact will block the whole box.

[2N3055]

I don't like the idea having such digital stuff next to some precision analog stuff.

Do you really need an automatic DIY multifunction calibrator for this purpose? I think having a box of artifacts is more useful. Therefore, everyone is able to compare the single resistors against each other and is also able to build known dividers and so on. Furthermore, connecting five resitors to the DMM isn't that time consuming, I think.

All these digital stuff, relais and switches will just increase the uncertainty of the stuff and a defective artifact will not block the whole box.

ATMega running of the 32kHz crystal, put in a sleep mode is for all the practical purposes off... We would use latching relays, so pulse on change then again quiet.. TiN said so because the more of the signal path is done right and characterised, it more likely it will have repeatable results.. If I don't do interconnections right, I will get huge errors just by using wrong wire...

[e61_phil]

You need a wire from the box to the DMM in any case.

And connecting a small box with 4 terminals (like the 10k reference Dr. Frank built) isn't harder to connect than a box with 4 terminals. I would invest my money rather in better artifacts than in expensive relays with very low thermal EMF. But this is just my opinion.

[2N3055]

You need a wire from the box to the DMM in any case.

And connecting a small box with 4 terminals (like the 10k reference Dr. Frank built) isn't harder to connect than a box with 4 terminals. I would invest my money rather in better artifacts than in expensive relays with very low thermal EMF. But this is just my opinion.

You have a valid point there, and I value your opinion.. Problem is that high quality connectors are going to be most expensive part....

[Nuno_pt]

Regarding the 100V part that enut11 talk about, Dr. Frank has build an precision divider box of 10:1 & 100:1 to get 100V & 1000V with very few ppm of the 10V with the LTZ, I know it's somewhere here in the forum but I can't find it now, I believe he even put the board layout in PDF and the schematic with the parts use, maybe Dr. Frank will stop by later and point to the right direction, this could be a good ideia for one to have at home, to calibrate the cardinal points at moderate cost.

I'm with e61_phil no need to make the things automated, with expansive reed relays and other stuff, but the logging should be automated like TiN suggested, logging the readings and Temp, Pressure and Humidity inside the box.

The resistors could be order from Edwin (member here on the forum) maybe he can do good prices for this.

As for the reference what would it be? LM399, 2DW23x, LM299, since the LTZ like TiN said could be expensive board.

[TiN]

There's no much point to spend an effort for box without environment logging integration.
Here I plot simple example of expected use scenario with few measurements, let's say 10V.
Red dots are ambient temperature when measurement was taken. Blue romb is voltage output reading.



I'd suggest e61_phil could estimate and tell us :

* How much reference output drifted after it was shipped back to User A ?
* What is uncertainty of transfer between User A data and rest of users?
* Which user's measurement is bad? 

Digital section would be fully isolated from analog, so there is no point in optical isolators/protection/etc. That's why I mentioned separate 5V jack, not take power from main 24V (two SLA battery) to analog section.

Reason for pi - easy and fast binding to internet (RJ45/Wifi), no problems storing megabytes of logs and data on internal 32GB SD card, small size, cheap.

Therefore, everyone is able to compare the single resistors against each other and is also able to build known dividers and so on.

Compare to 100ppm? Maybe. To 10ppm? Less so. To 2ppm? Very few members here able to do so.
Building dividers need expensive stable resistors too. If one has them and DMM already, they would unlikely be interested in discussed box anyway.

This brings bigger question. What specs are required for each of artifact. 1ppm? 10ppm? 50ppm? Design (and cost) would change a lot by this spec.

[e61_phil]

It is of course necessary to monitor the temperature and so on. But is a temperature and humdity logger which is shipped together with the other stuff not enough?

If you wan't to log all the data with the raspberry pi you have to support all the meters and the right interfaces (GPIB for example). Isn't it easier to set up a webpage which collects the data? Everyone can have a look at any time.

I'd suggest e61_phil could estimate and tell us :

I don't like it to talk that way. Let us stay objective. I don't want to say the approach with a DIY box is bad. I just wan't to ask critical if this way is really the best way to do it or is it much more effort than one need. Most of the people here in the thread have much more experience than me (especially you, TiN).

[TiN]

Excuse me if that sounded too harsh. I'm just looking on most nuts logs and posts and see often the case when temperature data is neglected. One temperature value for complete dataset is NOT enough, so temperature data has to correlate to measurememt logs.

From my experience, nobody has perfect stable 24.0c lab when doing voltnuttery, so it's important. Of course if we trying to get at least 10ppm. If it's 100ppm project, then things can simplify a lot.

Also when I start to comment here, idea of multiple same boxes was kept in mind. E.g. to send different regions or for sanity cross-checks. So having that BME280 data tied and unseparated from reference unit makes things much easier. If go all this effort to make international transfers, why skip on details?

Gpib/meter support can be added by participants separately as project evolves.

P.s. online data availability already done part for me, but I cannot say it's easy to understand data for everyone. 

[2N3055]

@TiN

I suggested low power uC, because I thought that with low power chip and 2032 battery (or supercap) it could be made to log even in transit.... With Mega32 i also can write to sd card easily, And with 328 we could even load Arduino bootloader if someone fancies that...

That was my rationale .. But that was only suggestion.

[Kleinstein]

Temperature logging is important. Here one might even need more than just one sensor, e.g. one for the room and one close to the resistors.

However I am not convinced that one needs to have the logging unit and much of the support along with the reference part. The logging part really depends on the meters, at least the software part.  For many the could something like a Raspi or an even smaller µC based unit. It does not make much sense to move this around as it really makes sense to have such a logger.

I would consider just moving around the actually critical reference part and keep most of the rest in the lab, even if this means you have to build it a 2nd or 4th time.

So in the extreme case the exchanged part would be only the voltage reference (with direct support circuit and likely 7 V -> 10 V step),  the dividers for 10 V -> 100 V and 10 V -> 1 V -> 0.1 V (if needed), a few resistors (maybe even shared with the dividers) and 1 or 2 temperature sensors.

The rest of the circuit to make this a small calibrator should not be that expensive and should be pretty much exchangeable.  So no need to also ship this part around every time - this could ease on shipping costs and ease on customs.

[guenthert]

From my experience, nobody has perfect stable 24.0c lab when doing voltnuttery, so it's important.

Well, the obvious solution (to me) would be to integrate an oven with controller.  Less than 0.5K drift can be achieved with a simple NTC and TL431.

[Nuno_pt]

That would be good to put all in one box, 7V->10V buffer, the dividers for 10V->100V->1000V and 10V->1->0.1V, and also the 100R, 1k, 10k, 100k, 1M, 10M, 100M resistors, the logging can be done with one BME280 inside the box, and an connection for an room BME280, that way it would log the 2 temp parameters, along with the rest of the measures.

About the resistores maybe the Econ 8G16A 0.01% 3ppm/C, but this only go to 500k, or ask the prices to Edwin maybe we could do some good prices.

For the dividers we could use the schematic from Dr. Frank, with is permission.

For the Reference seems that we're at LM399 (4 free samples from LT) or 2DW23x (cheap on Aliexpress), or maybe LTZ since it doesn't need the expensive Z-foil from Vishay, and we can get very good results with WW resistors, for the boards we could use some of the TiN or Andreas or other designs with LTZ or LM399.

[lukier]

I don't see the usefulness of such project. Correct me if I'm wrong. My thinking goes as such:

- if one needs to briefly check low to mid range DMMs then possibly the DMM Check or similar products are the way to go,
- for calibration, as someone mentioned already, dozens of calibration points are necessary, from DC to AC to current to ohms, for example just resistors required for my meters:
K2015 (K2000): 1k, 10k, 100k, 1M
K2001: 19k/20k, 1M
34401A: 100, 1k, 10k, 100k, 1M, 10M, 100M
3457A: 30, 300, 3k, 30k, 300k, 3M, 30M

that's a lot (15) of rather expensive resistors, that's why there are Fluke/Datron multifunction calibrators.

I see that RS will calibrate a bench meter for 62 GBP:
http://img-europe.electrocomponents.com/uk/img/site/campaigns/servicecentre/EMEA_0009_Calibration1-7-FINAL.pdf

That is cheaper than a DMMCheck Plus or building and shipping various gizmos. If one got a decent 6.5 digit meter for 200-300 GBP on eBay (typical prices for K2015 or 34401A) then 62 GBP is not that bad.

I'm not sure they do 6.5 digits (will be asking soon), but probably they do (they have 6ppm on 10VDC so that's probably a Fluke calibrator:
http://www.ukas.org/calibration/schedules/actual/0310Calibration%20Single.pdf)

So we've covered handhelds and bench meters up to 6.5 digits. For more serious stuff things get even worse, as calibrating 7.5 digit and higher requires very precise standards and often is only done properly by the manufacturer.

The only noble exception where this endeavour might make sense is HP 3458A, as it can calibrate itself from 10V and 10K. But in this case the travelling standard must be top-notch, on par with Fluke 732B and ESI SR-104 (maybe VHP101). I think forum users affluent enough to have 3458A would rather pay for Keysight calibration, maybe even the more expensive Loveland calibration against references tied to the Josephson Junction standard (0.014 ppm uncertainty on 10VDC).

[2N3055]

Well this would be like DMM Check for 6.5 dig DMM.. That is the point... And would be calibrated on a regular basis by people that know what they are doing.
That would give me enough confidence to know whether I need to send some equipment for adjustment or not..
That would be great help.. Also I would make one or two to keep and that way establish my own monitoring process..

I think that is worth a lot, and appreciate someone is willing to help with such effort..

Of course it would be easier to just send equipment to get calibrated.. If you can afford it..

[lukier]

Well this would be like DMM Check for 6.5 dig DMM.. That is the point... And would be calibrated on a regular basis by people that know what they are doing.

I see. Actually, I'll be building TiN's 2xLM399 board soon for a similar purpose (to check and perform user calibration on my K2001 that I've almost finished repairing).

Still 6.5 is can be quite demanding. All my meters have LM399 and being often sourced from eBay recyclers these are very old thus well aged references. I think to have decent TUR the travelling standard would have to be either preselected/aged multiple LM399 or LTZ1000 and it's where it becomes expensive. And then there are precision resistors, amplifier/divider for higher ranges, current sources and I don't even have an idea how to do a precise AC source.

Anyhow, I bet such DMMCheck 6.5 will be more expensive to build than just to pay for calibration

[Nuno_pt]

Well this project if it lift off and we can do this, will serve as a learning point both in Metrology and Electronics, and also to be able to *Cal* some of my gear and make measurements on how mine compare to the others or how much ppm it deviate from the last check, or how much drift relate to the Temp in the little house where I've my working bench.

The set WW precision resistores for an LTZ should be around 50 to 60€ maybe less, some parts can be sample from LT, probably Edwin can help also with WW for the decades at moderate cost.

I'm also be building 2 to 4 boards of TiN with 2xLM399, I've order 2 of each samples from LT, I'll order also samples for the parts that I can from LT or other places.

Next will 2 to 4 LTZ.
 

[BobsURuncle]

If you get enough people, someone in the group will always have a new and/or recently calibrated meter.  For example I have a new Keithley 7510, a 7.5 digiit DMM which is less than a year old - so still in calibration.  I would be willing to check some standards for some people if said persons pay for all the shipping costs.

[VintageNut]

If you get enough people, someone in the group will always have a new and/or recently calibrated meter.  For example I have a new Keithley 7510, a 7.5 digiit DMM which is less than a year old - so still in calibration.  I would be willing to check some standards for some people if said persons pay for all the shipping costs.

On the DMM7510, all of the ohms are 2-year same as 1-year. Fort DCV, the 2-yr is de-rated some from 1-yr.
You can use the first year to dial-in all of your DCV sources and then coast for year 2.

[hammy]

If you get enough people, someone in the group will always have a new and/or recently calibrated meter.

We could use a wiki page. Eyeryone who joins the group could add his dmm, including the calibration dates, to this wikipage. We send two or three standards in a circle always around, and everyone could enter the meassurements into the wiki page. If someone gets the standard, he can check his DMM against the others.

We do this in our country, and the shipping costs are low. Once a year we send a standard over the ocean to another measurement club and they send us vice versa their standard. In this way we could do a cross check.

I would join such a "measurement club" here in germany/europe. And I can offer hosting the wiki. Anyone interested?


 

[e61_phil]

I would like to join your idea hammy.

[Nuno_pt]

Well since I'm in EU, I'll join EU *club*, since the most near guys from me are in Germany.

[Nuno_pt]

Looking at some old threads from LTZ and looking at TiN website, I've gathering the following:

BOM from TiN website price today at Digikey;

311-10ERCT-ND - $0.99 -> 100
311-1.0KERCT-ND - $0.99 -> 100
311-1.0MERCT-ND  - $0.99 -> 100
SAM1061-04-ND - $10.99 -> 10
MAX6610AUT+TCT-ND - $21.17 -> 10
399-3905-1-ND - $19.04 -> 10
LTC2057IS8#PBF-ND - Samples LT -> 2 (here one can ask for 2 free samples at LT website)
P402KBCCT-ND - $9.40 -> 10
399-6417-1-ND - $11.39 -> 10
1N4148UR-1-ND - $19.60 -> 10
PZT3904CT-ND - $3.30 -> 10
1189-1818-1-ND - $15.25 -> 5

Total = $112.75

Resistors from Edwin prices from 2015;

120R - $6.85
1k - $6.34
10k - $7.43
12.5k - $7.43
70k - $12.38

Total = $40.43 for each board or 161.72€ for 4 boards.

LTZ1000ACH - $54.50 from LT
LTZ1000CH - $42.85 from LT

The order from Digikey can be split between all, that way would be cheaper to all, the WW resistors would be bought by each one depending on how many boards one want to build, the same with the LTZ.

I'll have to make the BOM for the 2xLM399 from TiN also.

[TiN]

I have to put a warning note, as my LM399 circuit values need corrections. Schematic also require few bodgewires to have proper operation with two LM399's.

LTZ one is good though.

[ez24]

Based on the posted responses so far, the original idea to fund the calibration of a member's high end DMM and use this to calibrate roving standards did not get enough support.

So, we need a source of parts and someone with metrology experience to build the cal standard.

Also useful would be a headcount of those interested in participating as well as country of residence.
enut11 (Australia)

Interesting.  I hope you can get this to work.   As someone said, customs could be a problem.  How about limit the devices to countries or regions, ie one for the US, one for Australia, one for Europe, etc.  Also shipping out of the US is very expensive.  Most in the know use shipping agents.   But start with one in your country (Australia) and if it works, try another one (in the US).

Maybe you can take a survey?  How much would a device cost? 

Good luck

[tautech]

Based on the posted responses so far, the original idea to fund the calibration of a member's high end DMM and use this to calibrate roving standards did not get enough support.

So, we need a source of parts and someone with metrology experience to build the cal standard.

Also useful would be a headcount of those interested in participating as well as country of residence.
enut11 (Australia)

Interesting.  I hope you can get this to work.   As someone said, customs could be a problem.  How about limit the devices to countries or regions, ie one for the US, one for Australia, one for Europe, etc.  Also shipping out of the US is very expensive.  Most in the know use shipping agents.   But start with one in your country (Australia) and if it works, try another one (in the US).

Maybe you can take a survey?  How much would a device cost? 

Good luck

The way around Customs is with Canet documentation.
Read this:
http://www.uscib.org/what-is-a-carnet-ud-1843/

This how touring bands/groups disclose the contents of their shipments of equipment.

[Nuno_pt]

I have to put a warning note, as my LM399 circuit values need corrections. Schematic also require few bodgewires to have proper operation with two LM399's.

LTZ one is good though.

TiN I've send an PM to plesa asking if he could provide the mods that he made to get the boards working.

Would it be feasible like in TiN 2xLM399 board to have 10V - 20V - 30V, maybe with one more LM? That way we could have 1A - 2A - 3A.

Mickle T. have made an DIY Calibrator here < https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg982223/#msg982223 >, with DCV 0.1, 1, 10, 100 V. DCI 10 mA, 1 A. Ohms 1k, 10k, 100k, 1M, in 3 small boxes.

If you could have the 10, 20, 30V, it could reach almost every DMM, K2000/15/1, HP 3456/7, 34401, etc....

[enut11]

OK, there seems to be interest from the EU, some from the USA but nil from Australia. It could mean that potential members are just too busy to get involved or have no need for this service. 

I am still hoping for more to come on board. Meanwhile I think that I will have to acquire metrology level building skills and will probably start with an LM399 voltage reference. Lots of Forum reading to catch up on...

TiN, how do I get hold of a couple of your dual-399 project PCBs?
enut11

[t2kv]

+1 for interest from Australia (Sydney).
(Subscribed to the thread, but forgot to jump in.)

[Dr. Frank]

If you get enough people, someone in the group will always have a new and/or recently calibrated meter.

We could use a wiki page. Eyeryone who joins the group could add his dmm, including the calibration dates, to this wikipage. We send two or three standards in a circle always around, and everyone could enter the meassurements into the wiki page. If someone gets the standard, he can check his DMM against the others.

We do this in our country, and the shipping costs are low. Once a year we send a standard over the ocean to another measurement club and they send us vice versa their standard. In this way we could do a cross check.

I would join such a "measurement club" here in germany/europe. And I can offer hosting the wiki. Anyone interested?

That common site would be a good idea, and a necessity for the exchange / circle-comparison of calibration data. I doubt, anyhow, that it's feasible to disclose publicly, visible to everybody, such confidential data, e.g. about individual possession of expensive instruments.

The technical exchange could only work properly, if travelling standards / calibrators of highest quality would be available. DMMCheckers and alike, or lower grade resistors are not suitable.

Reasons for my opinion:
1. Even if one member only wants to "check" his lower grade instruments, like e.g. 5 1/2 .. 6 1/2 DMMs, anyhow, sufficient T.U.R. is needed, so you easily end up with 1ppm uncertainty.
2. These standards, as they are exposed to rough environment on their travel, have to be extra stable and rugged, otherwise you won't have the chance that you ever get consistent values, after their return to the place of origin. Therefore, this excludes any simple or cheap solutions for these standards, probably also LM399's.
3. This initiative for sure aims also at volt-nuts, who already operate at the <= 1ppm uncertainty level.
If the travelling standards are less stable / uncertain than that, it would be completely uninteresting for these people.

Under these preconditions, I'm basically interested in such a group.

There already have been several personal  volt-nuts meetings with high grade equipment.
I personally prefer such events, over anonymous parcel shipping.

Frank

[Nuno_pt]

OK, there seems to be interest from the EU, some from the USA but nil from Australia. It could mean that potential members are just too busy to get involved or have no need for this service. 

Most of the guys that do this already have there own references build, and already sent them to others, like Dr. Frank said they do it in Germany, also Andreas told that we could send a reference out to others.

Has for me I'm probably going to make an TSB (Traveler Standard Box) with LM399 (here probably will use Mickle T. design for this) or LTZ with output of 7V, 10V and 10K 0.005% 3ppm/C PWW resistor from Edwin, when would be done will look for people to send it out.

I am still hoping for more to come on board. Meanwhile I think that I will have to acquire metrology level building skills and will probably start with an LM399 voltage reference. Lots of Forum reading to catch up on...

TiN, how do I get hold of a couple of your dual-399 project PCBs?
enut11

To get the boards you just have to go to TiN's website and download the Gerber files, but the 2xLM399 from TiN has some problem in the resistors networks look at the last page of the LM399 thread, also when TiN assemble one he put lots of bodge wires to make it work, also on the last page.

I don't know if TiN will do another board revision to fix this (because of his other projects and work), I know that @plesa has assemble 2 or 4 boards with UBX Vishay resistors and many PWW pots from Bourns.

A new design probably would be best to have 4xLM399 in one board since that way the noise is attenuate by a factor of 2, and is still economically acceptable, since you can get 4 LM399 from LT for free, 2 A version and 2 non-A.

 

[Nuno_pt]

The technical exchange could only work properly, if travelling standards / calibrators of highest quality would be available. DMMCheckers and alike, or lower grade resistors are not suitable.

Dr. Frank, here would the 0.01% or 0.005% 3ppm/C PWW resistors from Edwin or be acceptable?
Or must be Vishay VHP 101 or 202?
What values? 10k would be enough, or others are needed?
Also agree on DMMCheckers.

Reasons for my opinion:
1. Even if one member only wants to "check" his lower grade instruments, like e.g. 5 1/2 .. 6 1/2 DMMs, anyhow, sufficient T.U.R. is needed, so you easily end up with 1ppm uncertainty.

Would it be acceptable to do the measurements in 6 1/2 DMM? I've here 2 on way to 3, but don't know about the calibration state.

2. These standards, as they are exposed to rough environment on their travel, have to be extra stable and rugged, otherwise you won't have the chance that you ever get consistent values, after their return to the place of origin. Therefore, this excludes any simple or cheap solutions for these standards, probably also LM399's.

Also if it was 2 or 4xLM399?

3. This initiative for sure aims also at volt-nuts, who already operate at the <= 1ppm uncertainty level.
If the travelling standards are less stable / uncertain than that, it would be completely uninteresting for these people.

Agree, that for the already Volt-nuts, it would be uninteresting, but for newcomers would be good to learn with people that are already on this for long time.

Under these preconditions, I'm basically interested in such a group.

I would like to start somewhere.

There already have been several personal  volt-nuts meetings with high grade equipment.
I personally prefer such events, over anonymous parcel shipping.

Frank

I also prefer to meet in person, but given my case as an example, since I don't have any Volt-nut here in Portugal, after reading all the groups, for example it's easy to send my TS to you in Germany, then catch a flight to Germany, and maybe renting a car, etc..., the same could happen to others, if you've some people in your country or maybe neighbor country, it's ok to meet in person, but if not shipping is good.

No disrespect mean Dr. Frank.

Nuno

[HighVoltage]

I am interested in meeting in person but I also can help out, by sending a Geller Labs 10V reference, to those who are interested in seeing it on their equipment. I do have several of these 10V Geller Labs references and would make one available for traveling. But best to send it without the 24V DC power supply. You would have to power it with your own adapter or a lab PSU with 4 mm Banana plugs.

I would check the 10V reference on my 3458A, 34470A and DMM7510 before shipping and again when I receive it back.
May be even adjusting it as close as possible to 10.00000V
What I should do, is to install a PT100 RTD so we can also record the internal reference temperature when taking readings.



   

[VK5RC]

Apologies for late entry into this post, I just found it.
enut11
I am interested, in Australia, have a 3458A (out of cal). I am not at 1ppm level by quite some way.
Robert

[lukier]

A new design probably would be best to have 4xLM399 in one board since that way the noise is attenuate by a factor of 2, and is still economically acceptable, since you can get 4 LM399 from LT for free, 2 A version and 2 non-A.

I sense you have a laissez faire approach to samples. I wouldn't abuse sample programs like that and also encourage others to do so, in quantity. LM399 is a bit pricey, but not extremely and can be had cheaper on eBay.

There are really people that need these samples, in the academia, in startups and other legit business etc. There is a reason why being a volt-nut is an expensive hobby

[Kleinstein]

In a reference for calibration purpose the noise is not that important, as one can spend a little more (e.g. 2 or 4 times) time on averaging. So I don't think there is a real need to have more than one LM399 for noise reasons, unless you need a fast measurements or go beyond 8 digits.

It might be a reasonable Idea two have two references for a kind of self check - but this would be more like getting independent readings or average and difference.

For price of the LM399 circuit it really depends of one also includes the 7 V to 10 V circuit. The resistors for the 7 to 10 V step might be the more expensive part. The other parts should not be really expensive.

[enut11]

+1 for interest from Australia (Sydney).
(Subscribed to the thread, but forgot to jump in.)

Hi t2kv. Thanks for joining in. I am a novice volts-nut. What is your expertise? What type of DMM do you want to calibrate? I live in Wollongong, NSW and have an HP3456A (uncalibrated). enut11

Apologies for late entry into this post, I just found it.
enut11
I am interested, in Australia, have a 3458A (out of cal). I am not at 1ppm level by quite some way.
Robert

Hi VK5RC. Thanks for joining in. Having a 3458A is a good start, even if it is uncalibrated! What area do you live in? enut11

[t2kv]

Hi t2kv. Thanks for joining in. I am a novice volts-nut. What is your expertise?

I'm whatever the rank below novice is. I've done a bunch of little experiments comparing properties of commercial voltage standards in the 0.05-0.02% range, and built a resistance standard from 0.01% and 0.005% resistors.

What type of DMM do you want to calibrate?

One I haven't bought yet; I'm out hunting for a 6.5 digit multimeter at the moment.
The best I have at the moment is 4.5 digits, which is a bit embarrassing in the metrology section of the forum.

Hi VK5RC. Thanks for joining in. Having a 3458A is a good start, even if it is uncalibrated! What area do you live in? enut11

Based on the username, I'm guessing he is probably in SA. 

[hammy]

I'm whatever the rank below novice is.

 
We could split up Novice in Low/Mid/High 

[bitseeker]

I have several 6.5-digit bench DMMs (and lower-resolution handhelds) and am intrigued by the club concept, but need to see how it all comes together. The tradeoff will be cost vs. time required to perform the calibration and adjustment process myself as compared to occasionally using a local lab.

[VK5RC]

enut11,  I live in suburban Adelaide.
Regards Rob

[enut11]

I'm whatever the rank below novice is.

 
We could split up Novice in Low/Mid/High 

Maybe not such a crazy idea, at least we would know where we all stand wrt expertise.
Also, novices may be content with access to calibrated lower standards, such as DMMcheck or similar, while they are coming up to speed with knowledge and building skills.
enut11

http://www.voltagestandard.com/DMMCheck_Plus.html

[Alex Nikitin]

As an option - would it be an interest in a simple 10V/7V/10K travelling box, with 24V DC supply requirement, only two quality terminals and a 3-position switch (10V/10K/7V) ?

10K resistor would be hard-wired directly to the terminals so for the resistance standard the switch just disconnects the voltage reference, no contact resistance involved. This could be a very small, fairly accurate (probably under 10ppm for 90 days is achievable using LM399 and a good wire-wound resistor) and cheap unit. The 7V output would allow for a 7V to 10V transfer accuracy check limited only by the meter's ADC linearity error (so about 1ppm or better for decent 6.5+ digits units). 10K position also can be used to check the thermal offsets in the interconnects as long as the input current of the meter at 0V is low (1nA would create 10uV or 1ppm@10V error).

Cheers

Alex

P.S. from 10V and 10K anyone can derive other required DC references (i.e. 1K, 100K, 1M, 100mV, 1V, 100V, 1000V, 1mA, 10mA, 100mA, 1A etc) with a pretty good accuracy using the Hamon transfer method - as long as the resistors used in Hamon dividers have a reasonable short-term stability (and a low voltage coefficient for HV).

[Nuno_pt]

Alex, I'm looking at the same thing, but the difference will be 5 Pomona connectors, 7V directly from the Zener (maybe trimmer with Bourns PWW pot), 10V buffer from an LTC2057 (also trimmer), and 10k PWW from Edwin Pettis 0.005% 3ppm/C.

This would be box in a IP67 plastic or aluminum box, RPi Zero & BME280 inside to log, for power I was thinking maybe from battery (12V or 24V) or an wallwart could be use.

No switching involve from ranges.

[Alex Nikitin]

Alex, I'm looking at the same thing, but the difference will be 5 Pomona connectors, 7V directly from the Zener (maybe trimmer with Bourns PWW pot), 10V buffer from an LTC2057 (also trimmer), and 10k PWW from Edwin Pettis 0.005% 3ppm/C.

This would be box in a IP67 plastic or aluminum box, RPi Zero & BME280 inside to log, for power I was thinking maybe from battery (12V or 24V) or an wallwart could be use.

No switching involve from ranges.

It would be a lot more money  . And you shouldn't trim 7V from Zener (and 10V should not have a user accessible trim IMHO). Accurate multimeters would allow you to enter the actual value for 10V / 10K calibration, and not accurate meters won't need that accurate value anyway. Also you don't need a very expensive 0.005% 10K resistor. Even 0.1% will do nicely as long as the quality is good and the actual value is measured with good accuracy. Right now I can build one as I've described, with Pomona terminals and a Hammond aluminium box, for less than £70 even buying all parts from Digikey/Farnell.

Cheers

Alex

[enut11]

Cheap enough for each member to build his own and circulate it amongst the group.
Would a number of roving standards provide more useful information?

[3roomlab]

i had an idea once to want to fit out the insides of a pelican case with some resistors and standards to send to someone to help me determine some values, i didn't get around to do it.

so i think i will just put this idea in this thread, maybe the case is something like a box in a box suspended/shock-proofed? special air cushion? small enough that makes shipping affordable? or maybe not? i am guessing this equipment will be doing lots n lots of traveling, and things get hairy if it breaks due to rough cargo handling, it will really waste lots of time and effort. there could be live accelerometers to keep track of the journey so that the next user can help check if it went thru hell? then possibly look for damages and repair if any.

its just a thought

[ManateeMafia]

This case looks like it could be a good candidate. The lid is removable and perhaps add over the top plate a custom pcb with cutouts for binding posts switches, etc...

The plastic handle would probably have to go.

http://www.budind.com/view/Small+Metal+Electronics+Enclosures/Transi-Cases

[Alex Nikitin]

I would prefer a very small and light box - about 4'' x 3'' x 1''  which should survive any postal abuse. I've found a nice 10K 3ppm/C 0.1% 0.001% W/W resistor to use in it, by the way  .

Cheers

Alex

[Nuno_pt]

Alex, that is looking good, only.

[BradC]

OK, there seems to be interest from the EU, some from the USA but nil from Australia.

Count me interested. I'm in Perth and have a 3457A which is out of cal. I'm not a volt nut but I did build a 10V reference from an AD587KNZ to check my handheld meters. I use the 3457A for relative measurements, so I'm not in need of absolute accuracy. It'd be nice to know if it was close though (either it and/or my AD587 are within tolerance, but in which direction and how close is a mystery).

[guenthert]

I'm not a volt nut but I did build a 10V reference from an AD587KNZ to check my handheld meters.

That's the denial phase. 

[enut11]

Hi all. There are some wonderful suggestions in this thread and lots of expertise from long standind members. Inevitably there are different expectations and requirements depending on how high on the metrology ladder you are.

There is no reason that everyone could not be satisfied, but it is unlikely to happen with a single design. Also, unless something happens soon, this will end up being discussed forever.

May I suggest a staged approach:
1) We start with a simple but accurate and stable 10v (7v) and 10k roving standard to start the ball rolling.
2) If this works, and members are gathering useful information, we move to a more complex/versatile roving standard.
3) Finally, implementing an automated system loved by some of the more experienced members to save calibration time.

In the long term, I see a place for all three of the above as there will always be different levels of experience and different requirements.

If you accept this approach, please suggest a design and BOM for stage (1).
enut11

[retrolefty]

I'm not a volt nut but I did build a 10V reference from an AD587KNZ to check my handheld meters.

That's the denial phase. 

 Good one.  In my day we were satisfied with a fresh D cell as our reference. 

[VK5RC]

Hi All
Some Aussie guys are interested and emailing about voltage references, I am awaiting a good 10MOhm resistor.
In the meantime I downloaded RF Scientific's Data Logger program, I had a Prologix GPIB to USB interface, after a bit of problem with Win 7 making the logs file Read only, finally got it to work, imported into excel. I am not good at this stuff
Below is my first graph of data, no temp yet, It shows the early drift immediately after switch on of a 3458A (quite old - bought with dying NVRAM and transplanted old Cal data into new NVRAM) and KKMoon's old multi-voltage reference (eBay one).

[VK5RC]

Hi All,
A bit of a story, about a year ago I bought an old 3458A with the flat NVRAM battery problem, how I fixed it up (with a lot of help from TiN and other sources on the net) see  https://www.eevblog.com/forum/repair/minor-repair-hp3458a/
The problem is how good was the rest of the unit, it now passes self test and in comparison to an out of calibration 34461 it seemed reasonably accurate in terms of DCV, ACV, ohms.
I bought about 4 months ago a 03458-66509, the voltage reference unit out of 3458A, It only needs a single positive supply but it didn't come with the little (special) plastic cover for the LTZ1000ACH. Some of these surplus units on eBay are also of questionable heritage.

For a voltage reference unit I decided to use a metal box with polystyrene lining, I used a small cube of builders foam ( I heated it in the oven to 130C without adverse effect) and it isn't conductive - for the LTZ1000 cover.
For power I sought a low noise linear regulator, the TPS7A4901, seemed to fit the bill, certainly could cover the 30-40mA needed at 15V. An adapter board was used to get it onto my favourite one off project material , veroboard. The was fitted inside the box and was supplied from a lab PSU at 18V. The voltage supply is floating.
A Fluke temp probe was left inside the box so its temperature could be monitored during the experiments.
Photos of the inside of the box looking at the linear reg board. the top of the 03458-66509, the brown wire is the temp probe (K type)

[VK5RC]

The wire used to conduct the voltage reference is twisted pair silver coated copper, PTFE insulation and shielded. Like this http://www.ebay.com.au/itm/381447862950?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
The lugs I used came from JW Solutions. the 2758-fork from http://jswilley.com/Accessories.html - they are not cheap but are beautifully made.
Below is a photo of connecting them, I used Deoxit to clean the binding posts and the lugs before hand tightening the posts. The lugs are crimped then a light heat shrink applied.
The reference (metal) box is used inside another plastic box to try and reduce the effect of air currents and the terminals covered with a cloth

[VK5RC]

I tried to get a Rasp Pi talking to the 3458A to record the results but it was beyond my programming skills so I tried the RF Scientific freeware as I also had a Prologix GPIB USB adapter. I found it pretty easy. Below are my first results. DrFrank's comments re EMC effects were quite significant , about 10-50uV or so even with shielded cable bonded to the metal box of the reference and the guard post of the 3458A. Similarly door opening and closing in my small 'shack' ( I am an amateur radio op - total floor area ~12m>2).
Below are my results, the upper graph show my data over 8hours or so, the shack temperature slowly rose during the day from 17.5 C at the beginning to 18.2 at the end. The temperature inside the reference box was between 29.7 and 30.1C.
The two/3 dips in the raw data coincide when the 3458A was sampling just after I opened the door.

Settings 10V manual range, 4hr warm up then DC ACAL. NPLC 100, sampling every 120secs
The internal temp rose a little (31.5 to 32.1C) during the day and I recall its Internal last cal temp was in the mid 30s . I can't recall the Basic command to get it out of it again!

I am pretty happy with the results in terms of stability . I will repeat the whole setup soon to see if I get the same!
I wonder if the age of my unit (15+yrs or so) may have allowed the DMMs reference  to stabilise. My unit was obviously used pretty seriously before as it has been calibrated 16 times before, the last was by Agilent in 2009.
Any comments , suggestions or questions appreciated.
Thanks to dave, TiN, DrFrank, pelule, VintageNut, mimmus78, quarks and plesa and other EEV metrology contributors.

[plesa]

I tried to get a Rasp Pi talking to the 3458A to record the results but it was beyond my programming skills so I tried the RF Scientific freeware as I also had a Prologix GPIB USB adapter.

If you want I can post script for logging 3458A to file and website running on RPi2/3 which on webpage display the graphs.
Similar like TiN did on his website. 10MB csv take a few tens of second to redraw, but it is much faster that Excel
The tutorial on xDevs is slightly out of date.
Or if more members here will be interested I can make the RPi image ( Raspbian+GPIB+webpage) or send update to TiN to publish it.
After that you will needs to only make minor changes in scripts.
RPi should be better from EMI perspective than PC with monitor or laptop.

[TiN]

VK5RC

Good job on documenting, thanks for report. You don't really need to care on digits after 1uV, as they down in the noise anyway.
Also your reference output seem to be one of highest voltage I saw posted. I tend to think it's a good thing actually.

plesa

The tutorial on xDevs is slightly out of date.

But it woooorks!    

I know, could be better.

If you have image, I'd love to host it as well for 3458A newcomers.

[enut11]

@plesa
Yes please. I want to use RP3 to record data so any help welcome. Currently waiting for delivery of GPIB to USB converter.
enut11

[plesa]

The tutorial on xDevs is slightly out of date.
But it woooorks!    
I know, could be better.
If you have image, I'd love to host it as well for 3458A newcomers.

Started new thread and image will be ready soon with actual Raspbian.
https://www.eevblog.com/forum/metrology/raspberry-pi23-logging-platform-for-voltnuts/

[enut11]

@VK5RC
WRT the gold coated copper fork lugs, I could not see a price on the website without requesting a quote. Could you give an indicative price? These appear to be the best alternative to copper banana plugs.
enut11

[VK5RC]

@enut11, I can't recall the price, I have a vague+++ recollection it ended up being about AUD 5 each. I think quarks in his post https://www.eevblog.com/forum/metrology/diy-low-emf-cable-and-connectors/ reply no 16 in 2013 had them at just under USD$3 each.

[enut11]

Thanks VK5RC. At the other end, for boxed references, I was wondering if these copper terminals are suitable?
enut11
Look at this on eBay http://www.ebay.com/itm/201566753958

[TiN]

Look at this on eBay http://www.ebay.com/itm/201566753958

If one to pay 26$ for connector, I'd rather go to real deal for same money instead of shoddy ebay seller for audiophools.

[lukier]

If one to pay 26$ for connector

$26 for 4, which changes the game. But I'd be worried that these eBay audiofoolery ones are just copper plated or similar hoax. Maybe some forum member got a set and can confirm this is copper all the way through.

[plesa]

If one to pay 26$ for connector

$26 for 4, which changes the game. But I'd be worried that these eBay audiofoolery ones are just copper plated or similar hoax. Maybe some forum member got a set and can confirm this is copper all the way through.

It is 26 foe each Why not Pomona 3770 for $10?

[lukier]

It is 26 foe each Why not Pomona 3770 for $10?

I'm pretty sure the auction title says 4pcs, so $25.99 is for four, and the lowthermal one is similar price for qty 1.

[plesa]

It is 26 foe each Why not Pomona 3770 for $10?

I'm pretty sure the auction title says 4pcs, so $25.99 is for four, and the lowthermal one is similar price for qty 1.

I mean LowThermal. They are nice...

[VK5RC]

Thanks VK5RC. At the other end, for boxed references, I was wondering if these copper terminals are suitable?
enut11
Look at this on eBay http://www.ebay.com/itm/201566753958

At the  reference end , I have soldered the PTFE wire straight onto the circuit, means a slightly bulkier unit when not in use, but my thinking is that it avoids a set of metal to metal contacts out in the open  to potentially muck stuff up. While soldering has some issues, you will have to solder a jumper wire not only to the reference but also to the back end of the terminal.
I must admit to being a bit sceptical about those being pure copper, a comment of robrenz (in the quarks diy-low-emf leads post) is that pure copper is very difficult to work and those posts have a lot of detail, makes me think copper coated ?brass.

[plesa]

At the  reference end , I have soldered the PTFE wire straight onto the circuit, means a slightly bulkier unit when not in use, but my thinking is that it avoids a set of metal to metal contacts out in the open  to potentially muck stuff up. While soldering has some issues, you will have to solder a jumper wire not only to the reference but also to the back end of the terminal.

Majority of PCB with gold layer has copper-nickel-gold inter metalic structure instead of copper-gold. So EMF is still there.

[ez24]

Can someone give a summary of what is going on, ie a status report?  Is there something or is this just chit chat?
thanks

[t2kv]

Is there something or is this just chit chat?

Some of the Australians have started swapping references and sharing measurements. Not sure if there's any other activity.

[enut11]

Can someone give a summary of what is going on, ie a status report?  Is there something or is this just chit chat?
thanks

From what I can see the post has stalled somewhat. Whilst the idea of a calibration club has appealed to many, the practicalities have put a damper on it.

I feel that most of the voltnut expertise is in Europe (just an observation from the postings) and getting a design specified, approved, built and shipped (in particular internationally) has yet to inspire this group. Also, as already suggested, there is an ongoing local European club already doing something like this at local meetings.

There have been offers from eevblog forum members to circulate current worthy standards such as Geller, etc and but nothing has come of it.

I still feel that country/region based clubs is the way to go. However, until someone takes the plunge nothing will happen.

Meanwhile, in Australia, a number of junior voltnuts have banded together to initially share their mostly home-made standards. At least they will get the benefit of a 'second opinion' and gain more confidence in the accuracy of their meters. Currently all members have shipped their standards to one member who will measure all under the same conditions. All the standards are then posted to the next member, and so on. Hopefully it will grow from there to more serious standards sharing as experience is gained.

This is a call for action. If you think it is a good idea and want to be involved, tell us where you live and what you have to offer.
Then, you too may be able to form an Aussie-type club in your area or country.

The ultimate calibration club would be an international one but that will probably have to wait until another day.
enut11

[TiN]

Show stopper for me on this thread is lack of hard fixed specification of what are exact rules and requirements are.
Without this everyone would just do random things to random boxes, and there would be weak if any correlation between such "transfers".
Don't get me wrong, idea is good, but it's implementation is what makes it useful. 
I did international transfer on my DCV (<2ppm) and Ohms (<8ppm), so the whole concept is real, I assure you. 

I mean, just look at 2DWxxx low-noise zener thread. There are just 40 folks trying to get few pieces of simple zener, but there are already communication issues, someone get held up, others busy, and so forth.

Ideas like this must be run by dictatorship, with clear specs and fixed features. Otherwise everyone will just pull things sideways and apart.
Project leader has to define the direction and show the way to others. Then interested parties will jump in, if they willing to comply and commit.

[retrolefty]

Show stopper for me on this thread is lack of hard fixed specification of what are exact rules and requirements are.
Without this everyone would just do random things to random boxes, and there would be weak if any correlation between such "transfers".
Don't get me wrong, idea is good, but it's implementation is what makes it useful. 
I did international transfer on my DCV (<2ppm) and Ohms (<8ppm), so the whole concept is real, I assure you. 

I mean, just look at 2DWxxx low-noise zener thread. There are just 40 folks trying to get few pieces of simple zener, but there are already communication issues, someone get held up, others busy, and so forth.

Ideas like this must be run by dictatorship, with clear specs and fixed features. Otherwise everyone will just pull things sideways and apart.
Project leader has to define the direction and show the way to others. Then interested parties will jump in, if they willing to comply and commit.

 I agree, surely there is a Alfa Volt-Nut to lead the others. 

[ez24]

Ideas like this must be run by dictatorship, with clear specs and fixed features. Otherwise everyone will just pull things sideways and apart.
Project leader has to define the direction and show the way to others. Then interested parties will jump in, if they willing to comply and commit.

Totally agree this would be the only way - my vote goes to TiN since he has the calibrators

(just curious - did the name TiN come from the metal or a city ?)

[t2kv]

Ideas like this must be run by dictatorship, with clear specs and fixed features. Otherwise everyone will just pull things sideways and apart.
Project leader has to define the direction and show the way to others. Then interested parties will jump in, if they willing to comply and commit.

Agreed.

That said, this is what's just happened in the LTZ1000 thread, with TiN and a couple of others offering to calibrate others' boards against their kit. That sounds like the pragmatic start of a calibration club to me, particularly if those references then rotate within regions after cal.

[enut11]

Ideas like this must be run by dictatorship, with clear specs and fixed features. Otherwise everyone will just pull things sideways and apart.
Project leader has to define the direction and show the way to others. Then interested parties will jump in, if they willing to comply and commit.

Agreed. Must be a benevolent dictator  . He also needs to be a voltnut expert to create the proper specs suitable for the ongoing success of this Club.

[TiN]

my vote goes to TiN since he has the calibrators

Don't vote for me, I have enough backlogs to add one more fullblown endless  project. And calibrator is not relevant in this project case

(just curious - did the name TiN come from the metal or a city ?)

It's simple, first letters of my passport initials

[Theboel]

I vote for TiN but I am very patient until.
1. TiN someday visit to Yogyakarta or Borobudur temple with his LTZ boxes
2. My LTZ1000 and LM399 old enough and have calibrated against Indonesia NMI standard.
Until then I will waiting for any standard TiN has in his mind.

[Nuno_pt]

I would also vote for TiN, but is backlog is big so it's very difficult for him to lead a project like this.

I think that the best we can do is agree on specs for a Traveler Standard Box, like TiN KX LTZ1k board and 10k resistor with BME280 for logging temperature.

Since the calibrator will be very difficult to ship back and forward, a small TSB would be good.

I'll build one of TiN LTZ1k board for the TSB, I'm awaiting for Edwin set of resistors all with 0.1% 3ppm/C, and also a 10k 0.1% 3ppm/C for OHM transfer, the BME280 are on the way, the box will be a Hammond not shure what model yet.

[VK5RC]

Re travelling voltage standards I did a bit of an experiment today to see the effect of "careless" temperature management.
It started off cool here about 15C ambient/otdoor temp (0700) then heated uo to 38C max at about 1500hrs. My 'lab' started off at 21C ended up at 28C before I switched on air conditioner at 1700. The voltage reference was quite a bit hotter at about 34C.
I was also a lot more careless about door openings. The effect is dramatic. Moving references around will probably have a similar or even worse effect . I don't think the cargo hold is pressurised and can get really cold I believe.
One of the time-nuts actually dug a deep pit to get temperature stability for his frequency reference! Something to think about.
Below Blue trace is voltage on RHS, Orange trace is internal temp of 3458A, should be 37C (last cal temp)

[TiN]

Sorry, it doesn't look like your graph is showing anything, really, with due respect. First, if ambient temperature went up 7C, from 21 to 28 before AC on, it should have very similar effect on TEMP? output of the meter too. But that's not as issue, as reference output. It's span 7ppm, which is not what LTZ-based module should do, even on much largest temp span. So the setup is compromised and any correlation of temperature to output is just buried down down under the interference to LTZ module (be it EMI/RFI or air drafts or mechanical stress to cables or module).

Suggestions to improve:
* I don't know what logging sw you use, but add ACAL DCV function on each 0.5C of TEMP? change. This will remove tempco from your 3458A, down to <0.05ppm/K. My 3458A has tempco on 10V DCV range about 0.35ppm/K without ACAL, to give you the idea.
* Use twisted pair short copper wire between your DUT LTZ and 3458A. Put foam around binding posts to isolate from air drafts. You can use regular LAN UTP cable, it works great for this case. No need shmick 100$/meter teflon silver-99%-of-light phoolery here, just pure fresh cut copper will do great.
* Make sure your PSU is quiet. You can test it with 3458A , just log bit of data to see pk-pk. SMU should be fine, I use my 2400 all the time for LTZ tests, but I checked it before comparing with battery powered ref, to ensure setup is good.
* Turn off all PWM-dimmed lights in the room, those LED ones and such. Often the radiate into mains and that get coupled.
* Air drafts. Your biggest enemy with LTZ. Your task to have as still air possible. It also meaning filling with foam, just putting ref in the box not enough, as thermal gradients cause air to move.
* AC cooled room can oscillate. Meaning that your AC will be turning on and off to keep temperature setpoint, and that will cause temperature oscillation. I have it happening if I close the door in the room with gear and AC on. So I always leave door open and have AC only in the gear room, so hot air from outside dampen the temperature changes. By doing this I can reduce oscillation from ~1c down to ~0.2c. And it's no basement stuff (envy people with houses), just subtropical apartment building with thin walls and regular split HVAC unit.

[Dr. Frank]

Re travelling voltage standards I did a bit of an experiment today to see the effect of "careless" temperature management.
It started off cool here about 15C ambient/otdoor temp (0700) then heated uo to 38C max at about 1500hrs. My 'lab' started off at 21C ended up at 28C before I switched on air conditioner at 1700. The voltage reference was quite a bit hotter at about 34C.
I was also a lot more careless about door openings. The effect is dramatic. Moving references around will probably have a similar or even worse effect . I don't think the cargo hold is pressurised and can get really cold I believe.
One of the time-nuts actually dug a deep pit to get temperature stability for his frequency reference! Something to think about.
Below Blue trace is voltage on RHS, Orange trace is internal temp of 3458A, should be 37C (last cal temp)

Horrible jumps, even 7°C of fast temperature change won't explain these although the 3458A instrument has about 0.5ppm/K T.C. in that 10V range.
There's something fishy in your setup.

Frank

[VK5RC]

Thanks for the comments DrFrank and TiN
I agree it doesn't show just temperature effect,  I suspect it is many factors.  Unfortunately my current testing room is a lined and single insulated fibro-cement small room ie not very stable temperature wise.   I am using twisted pair,  shielded cables with a cloth cover over the terminals on the 3458,  the other end soldered on the pins that go directly into the 03458—66509 which is in a metal box inside a plastic container. 
My previous results with 'kid gloves'  were good,  i plan to experiment to see to what part of the later 'set'  up results in these fluctuations. The lights -  a smpsu (240-12v)with 12v LEDs look like a potential culprit,  it will be interesting to prove that or not. I have not taken one LED (Phillips Master series) apart to see if any internal  switching.  I have not had any RF (amateur bands) interference with them to date. 

[BradC]

Moving references around will probably have a similar or even worse effect . I don't think the cargo hold is pressurised and can get really cold I believe.

I would have thought moving references around would only have a dramatic effect if the extreme temperatures caused permanent changes in the characteristics. Letting things stabilize for a couple of days *should* allow things to return to normal again, otherwise how would meters make it around the globe and still maintain calibration.

I certainly don't intend to put my meter and reference in the hold of a 747 and have it log as it travels around the globe (although I'd jump if given the opportunity!).

[Edwin G. Pettis]

Air travel for precision standards are not recommended, the temperatures in the cargo hold can get quite cold, below -30°C and that can have a lasting effect on the standard.  While Evanohm based standards are more tolerant, they can still be affected to a significant degree when demanding better than 1 or 2 PPM accuracy, you can expect hysteresis of a few tenths of a PPM if you're lucky.  Manganin based standards will shift even more.  Shipping during the winter is likely to be even worse than the summer for airplanes.  Ground transportation should always be used if the standard must be shipped, granted it takes longer but it is relatively safer.  One other bug-a-boo, gorrilla handling in extreme cases can also cause a shift in value, standards always require kid glove handling for best long term stability.  This handling also goes for top level instrumentation, for the 3458A, to maintain best accuracy in high demanding applications, the instruments are 'hand' carried by ground transportation to the calibration lab, here in the states, that is in my home state of Colorado, Loveland to be specific and that service is around $1,800 from Keysight.

Since shipment produces something of an uncertainty into the equation, even for Evanohm resistors, a precise reading of the resistor(s) at manufacture may be changed slightly if poor conditions are encountered during shipping, only another precise reading at the receiving end can tell how much, if any, change occurred.  Even a highly stable resistor such as the SR-104 can be affected by bad handling.  Depending on the 'local' conditions, a given standard may have a limited accuracy (uncertainty) possible, with time and handling, repeated accurate readings will indicate just how stable the standard is going to be within the 'local' area of use.  No standard is absolutely stable even under the best of conditions, the change may be very small but change it will.

[Kleinstein]

In normal plane the cargo hold is pressurized, but even than the pressure goes down somewhat, e.g. equivalent to 3000 m altitude. Also pressure changes with altitude - so this could be a problem for instruments at high altitude. Hermetic sealed parts can see some stress.

Sometimes if you pay for ground transportation, you may still end up with your parcel send by air, just at low priority.

One crude check for stress during transport is to measure the reference before you send it out and compare when it comes back.

[Alex Nikitin]

I never thought that I would pay so much money for a single (and used!) resistor... . Nevertheless this addition to my home lab is rather nice and very welcome. Tomorrow I will get this cube to the HP3458A and see how time and various movements have affected it.

Cheers

Alex

[ManateeMafia]

Good score! These are nice resistors and it looks like yours was well kept. The rear decal shows no signs of tampering and the original alpha/beta values are still there.

Mine had loose binding posts and I had to open it. Someone also used some chemicals near the posts and it reacted with the plastic so beware of the urge to over clean it.
The black rubber feet all go bad eventually. They leave black residue on everything that comes in contact with them so I find myself removing them from time to time and replacing the bottom feet.

[Alex Nikitin]

Good score! These are nice resistors and it looks like yours was well kept. The rear decal shows no signs of tampering and the original alpha/beta values are still there.

Mine had loose binding posts and I had to open it. Someone also used some chemicals near the posts and it reacted with the plastic so beware of the urge to over clean it.
The black rubber feet all go bad eventually. They leave black residue on everything that comes in contact with them so I find myself removing them from time to time and replacing the bottom feet.

Thank you, it appears that my unit is indeed in a very good condition. I don't know how old it is, possibly over 10 years old from the look of it. My measurements at 23.5C on a freshly calibrated HP3458A Opt 002 show about +5.5ppm value , so about +6ppm possible shift from the original measured value (or less than the uncertainty of calibration for HP). The deviation on the HP meter from the calibration value was only +0.3ppm though. So far I'm quite happy with my purchase.

Cheers

Alex

[HighVoltage]

I never thought that I would pay so much money for a single (and used!) resistor... .

How much did you have to pay?
Was it over $ 500?

I am looking forward to your analysis with the 3458A

[TiN]

And since this thread derailed anyway, and if you have gear to run tempco test, I'd love to see the result on this 742A.
I wonder if it's worthy as travel transfer standard at ppm-level, or we still need oil-filled SR104. Manual and datasheet sorta vague about tempco spec.

[Alex Nikitin]

And since this thread derailed anyway, and if you have gear to run tempco test, I'd love to see the result on this 742A.
I wonder if it's worthy as travel transfer standard at ppm-level, or we still need oil-filled SR104. Manual and datasheet sorta vague about tempco spec.

Strictly speaking, the tempco is printed on the back of each unit and according to Fluke papers, these values do not change much with time * (unlike the resistance itself which may drifts at <2ppm/year rate according to the datasheet). Unfortunately, to calibrate this 342A properly might cost me almost as much as I've paid for it! One day I will consider it, till then I have to survive with a possible error up to 7.5ppm  .

Cheers

Alex

* - it does not mean I won't measure the tempco when I'll have a chance. At the moment I don't have a proper temperature chamber close enough to the HP3458A, and the tempco of the meter itself is probably much higher than that of the 342A, so changes in the ambient temperature can not be used reliably. I didn't run ACAL ALL on the HP meter for about a week (only ACAL DCV daily), and the measurements on the 342A before ACAL ALL today were 5.5ppm higher!

[Alex Nikitin]

I never thought that I would pay so much money for a single (and used!) resistor... .

How much did you have to pay?
Was it over $ 500?

I am looking forward to your analysis with the 3458A

It was about that figure (depending on the current exchange rate  it may be just over or just under $500  ).

Cheers

Alex

[TiN]

Tempco of 3458A can be limited pretty much to one of 40K resistor, if you add code into logging script to run ACAL DCV&OHM on each 1C of TEMP? change. That to be expected <1ppm/K.
What is printed is one thing, but it's interesting to see actual curve and it's slopes. It may or may not match the "typical" specs.

[Alex Nikitin]

Tempco of 3458A can be limited pretty much to one of 40K resistor, if you add code into logging script to run ACAL DCV&OHM on each 1C of TEMP? change. That to be expected <1ppm/K.
What is printed is one thing, but it's interesting to see actual curve and it's slopes. It may or may not match the "typical" specs.

The printed Alpha and Beta values are measured for each unit so aren't "typical". I was running the HP3458A and the Fluke for two hours, the lab temperature (and the internal temperature of the meter) went up by one degree C, the measured value decrised by about 0.7ppm. However when I've performed another ACAL OHM, the vealue went back to the measured just after the first ACAL earlier, within 0.1ppm. To get a reliable slope measurement in this situation I'll need a controlled temperature chamber (and a stable lab temperature).

Cheers

Alex

[enut11]

We need to get back on topic. Can this device be used as a roving standard for a forum calibration club?

[Alex Nikitin]

We need to get back on topic. Can this device be used as a roving standard for a forum calibration club?

No. But it can be used to calibrate a rowing standard - or several. Right now I have several wire-wound resistors that can be used as travelling standards. And I plan to make a travelling 1010 standard (10V/10K) soon.

Cheers

Alex

[CalMachine]

I would love to join this club!! 



I work and a 17025 accredited 3rd party cal lab and have pretty damn cheap electronic cal prices if anyone wants to send anything i to get calibrated.  Our price for 7.5 digit multimeters and lower is $85 (yes for an accredited cal).

I can list a lot of our standards we use and can even provide a copy of our scope if you'd like.

[enut11]

Hi calmachine. Please tell us more. Where do you live/work?

[CalMachine]

Hi calmachine. Please tell us more. Where do you live/work?

Hey Enut11!!  My name is Ryan and I work at ENI Labs in Ft. Wayne, Indiana!  Fully 17025 Accredited lab for most everything in the Metrology world!  I, myself, specialize in electronic calibrations and specifically 8.5 digit/dc/low freq.  Ever since I joined the Lab I've been pushing for better quality practices, procedures, and we are really have been investing a lot in upgrading our standards.   

If anyone has any questions, please feel free to ask

www.ENILabs.com
https://www.a2la.org/scopepdf/2147-01.pdf

[retrolefty]

Hi calmachine. Please tell us more. Where do you live/work?

Hey Enut11!!  My name is Ryan and I work at ENI Labs in Ft. Wayne, Indiana!  Fully 17025 Accredited lab for most everything in the Metrology world!  I, myself, specialize in electronic calibrations and specifically 8.5 digit/dc/low freq.  Ever since I joined the Lab I've been pushing for better quality practices, procedures, and we are really have been investing a lot in upgrading our standards.   

If anyone has any questions, please feel free to ask


www.ENILabs.com
https://www.a2la.org/scopepdf/2147-01.pdf

 What does it feel like to be paid to be a volt-nut? 

[CalMachine]

Hi calmachine. Please tell us more. Where do you live/work?

Hey Enut11!!  My name is Ryan and I work at ENI Labs in Ft. Wayne, Indiana!  Fully 17025 Accredited lab for most everything in the Metrology world!  I, myself, specialize in electronic calibrations and specifically 8.5 digit/dc/low freq.  Ever since I joined the Lab I've been pushing for better quality practices, procedures, and we are really have been investing a lot in upgrading our standards.   

If anyone has any questions, please feel free to ask


www.ENILabs.com
https://www.a2la.org/scopepdf/2147-01.pdf

 What does it feel like to be paid to be a volt-nut?

It's phenomenal and I am couldn't be happier this field. I wasn't a volt-nut / metrology-nut until about a year ago.  But I've been entrenched ever since!!  We've been making some big purchases to drastically increase our uncertainties and I am over here having the time of my life!  I'm pretty sure we're going to be snagging 1 of those Datron 4910s posted in the other thread.   

I plan on having a Quantum Hall Resistance system up and going by the middle of 2018.  And probably a Josephson Array shortly afterwards.  I'm so ecstatic for the future

[Dr. Frank]

We've been making some big purchases to drastically increase our uncertainties and I am over here having the time of my life!  I'm pretty sure we're going to be snagging 1 of those Datron 4910s posted in the other thread.   

I plan on having a Quantum Hall Resistance system up and going by the middle of 2018.  And probably a Josephson Array shortly afterwards.  I'm so ecstatic for the future

For sure you're ecstatic, I see.. But anyhow, you want for sure to decrease your uncertainty, aren't you? 

And obviously, you want to found another National Institute of Metrology.. I did not know yet, that any private company owns a QHR system, as it's yet more bulky and pricey than a JJA system, that huge dewar can and that strong superconducting many-Tesla-magnet..

Anyhow, if you succeed, especially in the year of 2018, you'd be well prepared for the new Si-2018! 

Frank

[CalMachine]

We've been making some big purchases to drastically increase our uncertainties and I am over here having the time of my life!  I'm pretty sure we're going to be snagging 1 of those Datron 4910s posted in the other thread.   

I plan on having a Quantum Hall Resistance system up and going by the middle of 2018.  And probably a Josephson Array shortly afterwards.  I'm so ecstatic for the future

For sure you're ecstatic, I see.. But anyhow, you want for sure to decrease your uncertainty, aren't you? 

And obviously, you want to found another National Institute of Metrology.. I did not know yet, that any private company owns a QHR system, as it's yet more bulky and pricey than a JJA system, that huge dewar can and that strong superconducting many-Tesla-magnet..

Anyhow, if you succeed, especially in the year of 2018, you'd be well prepared for the new Si-2018! 

Frank

Haha touche, I guess I mean't increase the greatness of our uncertainties! by lowering them.  But, turning our lab into a national standards institute is my end goal.  I would die a happy man.  I'm fairly young at 30, too!  So I've got plenty of time

But a QHR isn't too bad, especially now that graphene has been shown to be a viable medium.  You only need to get down to about 4K in about 5-10T to observe the QH effect.  There are multiple manufacturers we're looking at and so far some quotes have been ~ $250k for a cryogen free graphene QHR system...  which isn't TOO bad.

I have yet to look into a JJA system at all yet...  do you know a rough ballpark what one of those systems would run?

[Dr. Frank]

Commercial JJA systems are offered by hypres in U.S., the other is supracon in Germany.
They cost about 150-200k, a bit cheaper, as you don't need that magnet and big dewar.
The JJA may be produced by NIST or PTB, anyhow.

[CalMachine]

Commercial JJA systems are offered by hypres in U.S., the other is supracon in Germany.
They cost about 150-200k, a bit cheaper, as you don't need that magnet and big dewar.
The JJA may be produced by NIST or PTB, anyhow.

Awesome, thanks for the information!

[dr.diesel]

Hi calmachine. Please tell us more. Where do you live/work?

Hey Enut11!!  My name is Ryan and I work at ENI Labs in Ft. Wayne, Indiana!  Fully 17025 Accredited lab for most everything in the Metrology world!  I, myself, specialize in electronic calibrations and specifically 8.5 digit/dc/low freq.  Ever since I joined the Lab I've been pushing for better quality practices, procedures, and we are really have been investing a lot in upgrading our standards.   

If anyone has any questions, please feel free to ask

www.ENILabs.com
https://www.a2la.org/scopepdf/2147-01.pdf

WooHoo, this might be good news for me, I'm in Terre Haute!

[CalMachine]

Hi calmachine. Please tell us more. Where do you live/work?

Hey Enut11!!  My name is Ryan and I work at ENI Labs in Ft. Wayne, Indiana!  Fully 17025 Accredited lab for most everything in the Metrology world!  I, myself, specialize in electronic calibrations and specifically 8.5 digit/dc/low freq.  Ever since I joined the Lab I've been pushing for better quality practices, procedures, and we are really have been investing a lot in upgrading our standards.   

If anyone has any questions, please feel free to ask

www.ENILabs.com
https://www.a2la.org/scopepdf/2147-01.pdf

WooHoo, this might be good news for me, I'm in Terre Haute!

Sweet!!  Fairly close

[enut11]

Hi calmachine. Please tell us more. Where do you live/work?

Hey Enut11!!  My name is Ryan and I work at ENI Labs in Ft. Wayne, Indiana!  Fully 17025 Accredited lab for most everything in the Metrology world!  I, myself, specialize in electronic calibrations and specifically 8.5 digit/dc/low freq.  Ever since I joined the Lab I've been pushing for better quality practices, procedures, and we are really have been investing a lot in upgrading our standards.   

If anyone has any questions, please feel free to ask

www.ENILabs.com
https://www.a2la.org/scopepdf/2147-01.pdf

Hi Ryan. I should have guessed that you were in the USA! You are going to make a few American/Canadian voltnuts happy.
Maybe I could visit Indiana (from Australia) one day?

enut11

[TiN]

I have yet to look into a JJA system at all yet...  do you know a rough ballpark what one of those systems would run?

NIST SRI6000 10V PJVS system pricing is listed on  their site, 450K for compressor cooled all in one or 320K for LHe system. 10V JJA chip itself is 52.4K, 1V AC JVS - 26.3K .

Do you plan to calibrate DIY SSR/Resistance boxes, like LTZ1000-based/VPG foil 4W modules and such? Perhaps estimated ballpark pricing would benefit many of lurkers here, including myself.

[CalMachine]

I have yet to look into a JJA system at all yet...  do you know a rough ballpark what one of those systems would run?

NIST SRI6000 10V PJVS system pricing is listed on  their site, 450K for compressor cooled all in one or 320K for LHe system. 10V JJA chip itself is 52.4K, 1V AC JVS - 26.3K .

Do you plan to calibrate DIY SSR/Resistance boxes, like LTZ1000-based/VPG foil 4W modules and such? Perhaps estimated ballpark pricing would benefit many of lurkers here, including myself.

TiN, it would depend on the specs of the unit and the uncertainties in which you are looking for.  I'm sure we would have no issue providing accredited measurements on DIY equipment for $50-100 to hobbyists here at EEVblog!

[TiN]

I think specs would be in range <2ppm DCV, <8ppm Ohm (10k) so hopeless voltnuts with 3458 can benefit most, to have small reference box on 6/12 month rotation. You can also have a requirement for inbound SSR to be 0.5ppm stable within 7 days to ensure you not wasting time. So owner would need to do "pre-work" checklist on DUT reference to ensure this.

How about international shipment then? Small box with LTZ modules and resistors can be well below 5kg. Calibration for 1V, 10V, 10k, maybe 1 ohm. Usual procedure, similar to F732B and F742A can be used to make series of measurements over few days after 24h warmup. Such SSR box can have standard F732B ext battery DB9 connector port, to resolve PSU issues.

If you prefer, we can discuss over email details of such, but I think community can benefit a lot from having this info public. I'm not aware of any cal labs doing such service for hobbyists, esp. with international shipping.

[Nuno_pt]

I would join for calibrate my LTZ/10k box.

[CalMachine]

I think specs would be in range <2ppm DCV, <8ppm Ohm (10k) so hopeless voltnuts with 3458 can benefit most, to have small reference box on 6/12 month rotation. You can also have a requirement for inbound SSR to be 0.5ppm stable within 7 days to ensure you not wasting time. So owner would need to do "pre-work" checklist on DUT reference to ensure this.

How about international shipment then? Small box with LTZ modules and resistors can be well below 5kg. Calibration for 1V, 10V, 10k, maybe 1 ohm. Usual procedure, similar to F732B and F742A can be used to make series of measurements over few days after 24h warmup. Such SSR box can have standard F732B ext battery DB9 connector port, to resolve PSU issues.

If you prefer, we can discuss over email details of such, but I think community can benefit a lot from having this info public. I'm not aware of any cal labs doing such service for hobbyists, esp. with international shipping.

Unfortunately our DC/low frequency program isn't as robust as I would like it to be, that's why I am beefing up our procedures, standards, and getting some long-term data logging in place.  At the moment, we don't do long period temperature curves on resistances, which I also want to start providing to our customers.  All in due time

Also, if you're looking for those tight of specs, I can definitely give you some accredited measurements, however our *stated* uncertainties, depending on the range, could only yield a TUR as low as 2:1.  Once our next A2LA audit comes up, we will be seeking to lower our uncertainties significantly utilizing a lot of the new equipment we've been purchasing the last few months. 

As far as international shipping... I don't see that being much of a problem as long as you, the customer, is willing to pay for international shipping!

TiN, I've not seen any of these LTZ boxes you speak of... they sound pretty sweet!  I would love to give them a go...  and you say they have a 9pin DSub connector to plug into a F732B?

If you would like to discuss further, either on here or over email, don't hesitate to get ahold of me

[TiN]

At the moment, we don't do long period temperature curves on resistances, which I also want to start providing to our customers

I more meant that customer himself does "pre-test" before sending the box to you, and you just run it for few days (let box rest day 1, take 10 samples day 2, 10 other samples day 3, send unit back day 4, etc). Not necessary to have 24/7 longterm logging for calibration, you should expect already characterized reference at inbound. It's not the calibration lab job to do testing for the user, when asked (and paid for) only for calibration, which is measurement only, by the books. Hope this clarify things a bit, so we on same page.

As far as international shipping... I don't see that being much of a problem as long as you, the customer, is willing to pay for international shipping!

They'd better pay  . That sounds right, no problems. I just had different experience few years ago, when asked some cal labs to do same thing, with me paying shipping both ways, when I was looking to import DCV/Ohm into my homelab. I hand-carried standards and did own transfers since then, so it's less of an issue for me now, but I'd be looking for 3rd callab cross-check, and your service seem to fit great into the spot.

TiN, I've not seen any of these LTZ boxes you speak of... they sound pretty sweet!  I would love to give them a go...  and you say they have a 9pin DSub connector to plug into a F732B?

Well, the box I'm talking right now is not that refined, but I see no difficulty to prepare above-mentioned in Q3'2017 timeframe to perform a transfer. Since 2014 I was tinkering and had designed, built and tested compact 7V LTZ1000-based module following standard datasheet application almost exactly, and using bank of 4 modules as my homelab primary DCV standard, doing cross-checks from time to time. Design is fully open-hardware and covered in article on my site. One of latest modules was also tested in more detail covered here and discussed here and even got group of voltnuts to fab PCBs . For my first transfer in March'16 I've used standalone 3458A's A9 module to calibrate my first 3458A after repair. That got me to DCV within 6 ppm, which later in August was improved to <2ppm with bank of 8 x LTZ1000's (6 on my modules, 2 inside K2002's). For Ohms I use aged Vishay hermetic foils so far.

As of power port, it's easy to design in the enclosure to fit my references and provide DB9 interface, which can couple to 732B-7001 battery pack/charger. so you don't have to worry about finding power supply to power up the reference. International shipping is usually too long to have unit sent hot, and shipping large batteries require special permits/legalpapers anyway. So I'll have to test for hysteresis and stability after thermal shock first, before I have anything shipped. Surely other option to have regular mains PSU integrated as well, but that adds weight and size.

If you would like to discuss further, either on here or over email, don't hesitate to get ahold of me

Thanks for being transparent for hobby level things, this is rare thing in metrology market. We can keep discussion here for time being, as things covered are pretty generic. You will get line of voltnuts lineup with their boxes quicker than you realize 

[CalMachine]

At the moment, we don't do long period temperature curves on resistances, which I also want to start providing to our customers

I more meant that customer himself does "pre-test" before sending the box to you, and you just run it for few days (let box rest day 1, take 10 samples day 2, 10 other samples day 3, send unit back day 4, etc). Not necessary to have 24/7 longterm logging for calibration, you should expect already characterized reference at inbound. It's not the calibration lab job to do testing for the user, when asked (and paid for) only for calibration, which is measurement only, by the books. Hope this clarify things a bit, so we on same page.

Well, sometimes we do take special requests for testing parameters on a particular unit, if customers have them.  That can definitely up the price of the cal though.  But yes, you are correct... we generally only take measurements, and adjust if possible/needed.

As far as international shipping... I don't see that being much of a problem as long as you, the customer, is willing to pay for international shipping!

They'd better pay  . That sounds right, no problems. I just had different experience few years ago, when asked some cal labs to do same thing, with me paying shipping both ways, when I was looking to import DCV/Ohm into my homelab. I hand-carried standards and did own transfers since then, so it's less of an issue for me now, but I'd be looking for 3rd callab cross-check, and your service seem to fit great into the spot.

Ahh, sorry to hear about your past experiences.  And yeah, we purchase used test equipment internationally sometimes.  Like that Datron 4910 we might get from that German company you linked in the other thread (I believe it was you).

TiN, I've not seen any of these LTZ boxes you speak of... they sound pretty sweet!  I would love to give them a go...  and you say they have a 9pin DSub connector to plug into a F732B?

Well, the box I'm talking right now is not that refined, but I see no difficulty to prepare above-mentioned in Q3'2017 timeframe to perform a transfer. Since 2014 I was tinkering and had designed, built and tested compact 7V LTZ1000-based module following standard datasheet application almost exactly, and using bank of 4 modules as my homelab primary DCV standard, doing cross-checks from time to time. Design is fully open-hardware and covered in article on my site. One of latest modules was also tested in more detail covered here and discussed here and even got group of voltnuts to fab PCBs . For my first transfer in March'16 I've used standalone 3458A's A9 module to calibrate my first 3458A after repair. That got me to DCV within 6 ppm, which later in August was improved to <2ppm with bank of 8 x LTZ1000's (6 on my modules, 2 inside K2002's). For Ohms I use aged Vishay hermetic foils so far.

As of power port, it's easy to design in the enclosure to fit my references and provide DB9 interface, which can couple to 732B-7001 battery pack/charger. so you don't have to worry about finding power supply to power up the reference. International shipping is usually too long to have unit sent hot, and shipping large batteries require special permits/legalpapers anyway. So I'll have to test for hysteresis and stability after thermal shock first, before I have anything shipped. Surely other option to have regular mains PSU integrated as well, but that adds weight and size.

That module you designed is fantastic!  I love it.  I am definitely trying to get into the design side of things.  Do any of you here see a market for 10.5 digit multimeters?  I've been thinking about trying to design one in my off time.  First though, I was going to try to design a new way to get a more accurate voltage reference.  This is probably a few years in the making, however lol.... As I delve into it, it could very well be a thing that's not feasible.  I will definitely be looking to some of the great information I've found on this website when I get the go ahead.

If you would like to discuss further, either on here or over email, don't hesitate to get ahold of me

Thanks for being transparent for hobby level things, this is rare thing in metrology market. We can keep discussion here for time being, as things covered are pretty generic. You will get line of voltnuts lineup with their boxes quicker than you realize 

You are very welcome!  I try to be as transparent as possible, as I know a lot of the other cal labs I've dealt with can be pretty shady.  I've gotten multiple suspect cals from labs I thought were pretty reputable.

[TiN]

Unless one can design JJA which runs at LN2 temps, there is no possibility of 9.5 digit "DMM" smaller than few 42" tall 19" racks and taking few KW of power. Limitation of performance is the reference in most aspects. Conditioned LTZ1000 bank gives you noise/short-term stability in range 0.2-0.4ppm, so even if you pay few M$ to design and make ultralinear ADC you will be limited by this number.
For resistance it's bit better, as you can apply ratiometric measurements with DCCT bridge to get 9.5 digits, but thats still a 42" rack of equipment. Check Measurement International site, they have such system for sale.
JJA-based voltmeter also exists, made by Supracon ?G/PTB.

[e61_phil]

But even an ADC in the same class as the 3458A would be very interesting. CalMachine how would you like to realize that?

[CalMachine]

Unless one can design JJA which runs at LN2 temps, there is no possibility of 9.5 digit "DMM" smaller than few 42" tall 19" racks and taking few KW of power. Limitation of performance is the reference in most aspects. Conditioned LTZ1000 bank gives you noise/short-term stability in range 0.2-0.4ppm, so even if you pay few M$ to design and make ultralinear ADC you will be limited by this number.

Oh! That makes sense.  What if one was able to design something more stable with less noise than the tried and true LTZ1000 references?  The new DMM I have in mind would be very similar to the Datron 4950... where it can measure only in small bands, EXTREMELY accurately.  Mostly for metrology purposes, and not for general measuring applications.  One big thing I would like to incorporate into it is; referenced to quantum realization of the SI units as opposed to normal primary or secondary standards.

For resistance it's bit better, as you can apply ratiometric measurements with DCCT bridge to get 9.5 digits, but thats still a 42" rack of equipment. Check Measurement International site, they have such system for sale.
JJA-based voltmeter also exists, made by Supracon ?G/PTB.

Oh wow,  Thank you for showing me this company!  I didn't think there were many companies out there developing test equipment utilizing the new quantum standards. 

But even an ADC in the same class as the 3458A would be very interesting. CalMachine how would you like to realize that?

Can you elaborate a little bit on your question?

[Dr. Frank]

Like that Datron 4910 we might get from that German company you linked in the other thread (I believe it was you).

They are called "Singer Pharmacy", as they are totally overprized, and they often have very old stuff, w/o advising you, about ser. no. / date codes and real condition.
The instruments work all right, though, because they have a bunch of skilled technicians in their cave.
Sometimes, they sell instruments as "scrap" for a reasonable price, and these turn out sometimes to work fine, as my Fluke 5200A for a few hundred €uro.

Over 20 years ago, I've already bought several special RF tubes for our Aachen Physics II Institute directly from Helmut Singer.. he's quite a rustic guy..
 

That module you designed is fantastic!  I love it.  I am definitely trying to get into the design side of things. 

Please check out our Super LTZ thread, https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/, there are many other designs also, which have some advantages over the original schematic from LT, with less engineering effort and cost... Look for Andreas PCB, for example.

Do any of you here see a market for 10.5 digit multimeters?  I've been thinking about trying to design one in my off time.  First though, I was going to try to design a new way to get a more accurate voltage reference.  This is probably a few years in the making, however lol.... As I delve into it, it could very well be a thing that's not feasible.  I will definitely be looking to some of the great information I've found on this website when I get the go ahead.

This has already been discussed in several threads.
An analogue DMM with more than 8 1/2 digits is useless at this time, due to physical linearity and noise limitations.
As an analogue voltage reference, there is currently no other more stable device available than using zener diodes (reference amplifiers).
Drift is on the order of a few parts in 10^7/year, noise on the same order, again limiting useful uncertainty, and the resolution to about 8 digits.
See DMM noise comparison thread for that.

I've seen a concept, where a JJA as an A/D and reference is combined directly with a DMM, so to maybe have order of 10^-9 of noise/stability/uncertainty..
For physical reasons, as soon as you go from cryogenic/quantum world to real 300K analogue world, you will be limited to these 10^-9.

So there's not only no market for 9..10 digits analogue DMM, these simply do not exist.

Frank

[CalMachine]

They are called "Singer Pharmacy", as they are totally overprized, and they often have very old stuff, w/o advising you, about ser. no. / date codes and real condition.
The instruments work all right, though, because they have a bunch of skilled technicians in their cave.
Sometimes, they sell instruments as "scrap" for a reasonable price, and these turn out sometimes to work fine, as my Fluke 5200A for a few hundred €uro.

Over 20 years ago, I've already bought several special RF tubes for our Aachen Physics II Institute directly from Helmut Singer.. he's quite a rustic guy..

Thanks for the information!  I'll see what kind of information I can get about the unit before we make the purchase.
 

Please check out our Super LTZ thread, https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/, there are many other designs also, which have some advantages over the original schematic from LT, with less engineering effort and cost... Look for Andreas PCB, for example.

I will definitely do that.  There has been some amazing work done by you all so far.  Very well done.

This has already been discussed in several threads.
An analogue DMM with more than 8 1/2 digits is useless at this time, due to physical linearity and noise limitations.
As an analogue voltage reference, there is currently no other more stable device available than using zener diodes (reference amplifiers).
Drift is on the order of a few parts in 10^7/year, noise on the same order, again limiting useful uncertainty, and the resolution to about 8 digits.
See DMM noise comparison thread for that.

I've seen a concept, where a JJA as an A/D and reference is combined directly with a DMM, so to maybe have order of 10^-9 of noise/stability/uncertainty..
For physical reasons, as soon as you go from cryogenic/quantum world to real 300K analogue world, you will be limited to these 10^-9.

So there's not only no market for 9..10 digits analogue DMM, these simply do not exist.

Frank

Hmmm well that's some food for thought.  You have some great insight!  I'm definitely going to take some time to digest this and see whats going on.  One of the things I wanted to incorporate was a specific resistance range to measure the Von Klitzing constant.   Maybe my eyes are too big for my mouth lol

And yeah, I realize that 8.5 DMMs are the longest scale out there right now... that's why I was maybe wanting to develop a 9.5 or even 10.5 DMM, but it sounds like it's going to take some serious design improvements along with maybe some quantum references.

[dr.diesel]

Even the big guns would struggle with a new true low noise/PPM 8.5 digit meter, 9.5 digit might be doable in theory today, but 10.5 IMO would take the collaboration of all involved and likely cost > $1B and 10+ years of serious development.  10.5 would take guts not even invented yet.

In any case, I'm struggling to think of even an uber niche need for such a 10.5 digit meter?  Aside form a few guys here sales would likely be very low, 

[enut11]

@calmachine
Hi Calmachine. Your offered services will be of much value to many (mainly local USA) voltnuts as well as those at the top of their game regardless of location.
However, we need to keep this thread on topic and find a practical way to help voltnuts, located in different parts of the world, check their out-of-cal 6.5 to 8.5 DMMs. A lot of these enthusiasts have home-made voltage references of different grades. So, for many, a stable reading using a calibrated DMM (eg HP3458A) would suffice.

From my pespective, this can be successful done provided each country has an affordable service such as yours. In reality, I think we have to find a way to help ourselves because the practicalities of international roving standards has yet to be resolved.

[TiN]

enut11

My personal 5c that given cost numbers from CalMachine for measurement/check it would be hard to beat, even including shipping to and from USA. Would you spend 300$ to design a box with reference and resistor, when you can just send your meter altogether and get it calibrated for similar sum? Unless you have more than few meters, this is viable way too. So I'd say this discussion is very well on-topic. There are still no specs/requirements defined and no-one seem to have large enough loads of time required to actually build first roving box to make this Club talk practical.

Surely CalMachine can start separate thread, called "Hobby-level calibrations service" or something like that if he desire to keep all eggs in one barn. 

[enut11]

@TiN
Yes it would be tempting to take up Calachine's offer from Australia but for the risks involved with international shipping. My HP3456A, purchased working from the USA, arrived with several errors. I found 2 dislodged PCBs, most likely due to rough handling. Hence my suspicion of this working for me - would I be confident of receiving a calibrated meter for my $300?

[e61_phil]

And yeah, I realize that 8.5 DMMs are the longest scale out there right now... that's why I was maybe wanting to develop a 9.5 or even 10.5 DMM, but it sounds like it's going to take some serious design improvements along with maybe some quantum references.

If you want more resultion only, you can connect a 3458A via GPIB and you will get more than 8.5 digits... I'm still interested in how do you want to achieve (with DIY methods) an ADC which is at least as linear as the 3458As one?

[TiN]

enut11

You already know the answer - only one way to find out, pack the box well, talk with CalMachine and sent it. We all can learn from outcome, before sending ours 3458A to him .
Of course your mileage will vary, but ALL my gear comes internationally, mostly from US eBay. Only once I had problem, with 4263B, broken front panel plastic due to horrid packaging with just tightly fit single layer cardboard box.

That's also reason why I usually never question shipping cost, which could be sometimes 30-100% of unit cost. Bright example was Agilent 4142B. Unit itself - 220$. Shipping of it : 250$ due to 29.9kg weight and size (4U frame 750mm deep).

And again, if you pay 100$ for shipping each way, and 100$ for cal of your 3456A, you will get much better bang per buck than spending same 300$ for building 10v, 10k reference box (which you still need pay for ship to someone for calibration and pay for it to come back). And that leaves you without current ranges except 1mA, without high/low voltage and without ACV/ACI and makes you need MFC/sources to transfer your reference values into same 3456A. To me choice is obvious

[Dr. Frank]

I found this AC Quantum Voltmeter, if somebody needs a 10 digit DVM, here it is:

http://www.supracon.com/en/ac_quantum_voltmeter.html

That's a cooperation of PTB and the companies esz and Supracon, latter offers JJA systems, also.

That system is able to measure DCV and ACV to about +/-10V with 0.1nV/V (10digits) uncertainty for DCV.. JJA serves as reference and D/A, obviously.

Frank



Frank

[mimmus78]

Ahhh!!! I just brought a 3458a ... it will never ends!

Inviato dal mio Nexus 6P utilizzando Tapatalk

[dr.diesel]

it will never ends!

Dang technology!   

I took the post about 9.5/10.5 digit meters as in something in a reasonable form-factor, not considering stuff with multiple kWs of consumption that arrives on a semi and requires a forklift to unload!

You pretty much have the best money can buy at the moment.

[mimmus78]

Form factor, consumption ... does it really matter!?

Inviato dal mio Nexus 6P utilizzando Tapatalk

[CalMachine]

And yeah, I realize that 8.5 DMMs are the longest scale out there right now... that's why I was maybe wanting to develop a 9.5 or even 10.5 DMM, but it sounds like it's going to take some serious design improvements along with maybe some quantum references.

If you want more resultion only, you can connect a 3458A via GPIB and you will get more than 8.5 digits... I'm still interested in how do you want to achieve (with DIY methods) an ADC which is at least as linear as the 3458As one?

I am not sure... this is in the infancy stage of just an idea that I have.

I found this AC Quantum Voltmeter, if somebody needs a 10 digit DVM, here it is:

http://www.supracon.com/en/ac_quantum_voltmeter.html

That's a cooperation of PTB and the companies esz and Supracon, latter offers JJA systems, also.

That system is able to measure DCV and ACV to about +/-10V with 0.1nV/V (10digits) uncertainty for DCV.. JJA serves as reference and D/A, obviously.

Frank

This is amazing!  This is the type of stuff I'm shooting for.  Maybe I need to go back to school for a physics degree!

it will never ends!

Dang technology!   

I took the post about 9.5/10.5 digit meters as in something in a reasonable form-factor, not considering stuff with multiple kWs of consumption that arrives on a semi and requires a forklift to unload!

You pretty much have the best money can buy at the moment.

Yeah the form factor I would try to design the unit around would be, like, the size of a Fluke 5700 or Datron 4808/4708

[Theboel]

Hi,

One think I like to do if I have access to lab standard is made a history of my own standard in control environment for a long time with let say 90 days interval let say in 2 years long with this work I can made a prediction about drift and accuracy in longer term.
   

[technix]

I wonder how much would this cost. I have a LM399 and an ADR03B chips to calibrate. Maybe I will calibrate my UT61D multimeter too.

[Theboel]

I wonder how much would this cost. I have a LM399 and an ADR03B chips to calibrate. Maybe I will calibrate my UT61D multimeter too.

I don't know how Your country tax policy, but from experience annually send my VNA calibration kit to overseas lab the shipment and tax are killing factor compare to my NMI cal

[VK5RC]

There is 'a bit' of an 'Aussie Cal Club' going - thanks to enut11 et al.

Thanks to TiN and minnimus78 and others for the run of TiN's KX boards (see xdevs.com/article/kx-ref for excellent background on the development)
After a bit of a struggle getting some good Vishay resistors into Australia - [as opposed to Ultohm Plus/Mr Pettis, who was so helpful and a delight to deal with, thanks again]  I have built three LTZ reference boards.
One has an LTZ1000CH with Ultohm Plus resistors (Mr Pettis)
One has an LTZ1000ACH with Ultohm resistors
One has an LTX1000ACH with mostly Vishay Precisions ( and one Mr Pettis Res - VK5RC stuffed up his order with Vishay!!!!!)
Currently they are 'running in', I aim to put ~400hours or so on them.
I boxed them in a cast metal box with some foam insulation which is then placed inside a plastic box for a bit more thermal insulation. They are powered by a linear PSU using a TPS7A49 low noise regulator putting out 15V, this is mounted in its own metal case nearby but 'out in the open' - to minimise heat transfer.
The PSU receives 18V from another linear PSU LM7xx series.
The resistors and LTZ are mounted just a little off the PCB so I could get a decent set of haemostat forceps in there during soldering to minimise heat stress. So far early drift (by simple measurement) has only been around 1 ppm.
Still undecided re logging strategy, my Linux/Rasp Pi/Python abilities are terrible, IanJ's excel macro/82357A or RF scientific/Prologix are possibilities.
With thanks to EEVblog Metrology forum contributors for helping me get this far
Robert

[TiN]

What is your next step in plan? If you wish to perform a transfer using one of modules with cross-shipping (I'd assume Australia-Taiwan be fairly cheap), you can include RPI3 with it and I can set it all up for you, so it will be as easy to start logging as entering one command ./make_me_logging.sh 

[VK5RC]

TiN,  that is a great  offer,  I would be delighted to accept,  I would want to be sure the unit I send is reasonably stable,   along with a RPi3,  this might take me a week or two.
I am reasonably happy my 3458 is moderately stable: It mainly lives switched off but if I warm everything up properly,  and read either,  1 an old separate 3458 voltage reference or,  2 my fluke 731b,  over the last 2-3 months,  I am getting readings consistent to around 2 to 5 uV.  Over many hours the results are better. 
Regards Rob

[TiN]

Sure, I'd expect to get reference to settle first 200+ hours. Then similar would need to be happen here, log for week or two to make sure it's all good and stable.
As bonus I'd be able to run tempco curve for you

[enut11]

Hi VK5RC. Great implementation of LTZ1000 refs. Now that I have successfully built a couple of LM399 refs I am looking forward to getting stuck into an LTZ project. Just need to source a PCB. BTW, any idea of the total cost of one completed ref?
enut11

[VK5RC]

Hi enut11,
The Vishays were crazy in price AUD $80+ EACH ! (Vishay sent me to an Asian distributor) The Ultrohm Plus resistors despite being prob very close in quality (I am not qualified to say) but were a fraction of the price, I recall about USD$5-10 each and Ultrohm was so much easier to deal with. Mr Pettis is a contributor to this forum - in the future it will definitely be Ultrohm for me.

The LTZ1000ACH I could only get from Digikey and were ~ AUD$80 ! I think the LTZ1000CH were a bit over half price.
The other components are pretty cheap. TiN on his KX reference article has a list of components and the price he could get them for - getting the Vishays in Australia was quite a bit more than TiN could in Taiwan.

Getting an old (but hopefully not buggered) 3458 reference board starts to look not bad value (often around USD240). The one I got is OK (I think!).

I am tempted later to try and make a 'rough and ready/good value' reference using an LTZ1000CH, a few well placed good resistors (some are more critical - I recall the 120R) on veroboard ! Just to see what difference it makes! HiHi.

I think I saw your 399s on another post - nice units!

Robert

[Kleinstein]

The vertical mounting of the PWW resistors is not such a good idea: this way the temperature at both ends of the resistor can be a little different and thus thermal EMF could be an issue. Ideally the resistors should be mounted horizontally with wires of equal length. So the PWW resistors should get a slightly different layout. The 70 K resistors are already less critical than the others - so I don't see a reason for the metal canned ones here.

The way the board is mounted looks strange - looks like possible mechanical bending the the board. This is usually something one wants to avoid. So ideally more like one fixed point and maybe 3 more with a little room for free movement.
Having a full metal enclosure is a good idea.

[Alex Nikitin]

My "1010B" reference box is available now in the UK for any EEV forum member who needs a quick check with a better than 50ppm uncertainty - please PM me if interested. The reference provides 10V with a low output impedance, 1V with 1K output impedance (so the value will be off by -0.01% on 10M load), 10K and 1K resistance (hermetic bulk foil). The stability for 3 weeks running (~500 hours) is very good, the temperature coefficient is about +1ppm/C for the voltage and less than 3ppm/C for the resistance. I will send this unit out with two conditions - the time to return should be less that ten days and the unit should be sent back by Special Delivery. I would prefer to get the reference back to my place every time as it would allow me to check it before sending it out again. 10v output is adjusted for 10.00000V at 23C, the actual measured values for 1V output, 10K and 1K resistance are marked on the reference case. The power supply could be from 16 to 26V DC, a couple of 9V batteries in series will do nicely, as the current consumption is low (~4mA) and a warm-up time from cold to <5ppm of a final value is about 10min . I can send a simple 24V switcher with the reference if required (I use a 24V stabilised linear supply with it, but it is quite heavy).
 
Cheers

Alex

[VK5RC]

Doing a few experiments to see if I really understand my vol-nut set-up ( the answer is I don't fully - yet ) I think I still have a few - I think - possible ground loop - gremlins.
 
Today was quite hot day (outside Min 18C max 33C)- 3458 warmed up overnight - mine is usually about 16C above ambient - below are some graphs of the measured voltage of an (TiNs KX design PCB - Thanks again to TiN for design and minimus78 for the PCB run) with Ultrohm (Mr Pettis' ) resistors and LTZ100ACH reference.
I am currently using a Prologix GPIB USB interface and 'RFScientific' program on a PC. Only one ACAL DCV at the beginning - clearly against the protocol - where it should be done every degree C change.
The bottom graph is the measured voltage which altered over the day (and room temperature) The airconditioning (reverse cycle hole in the wall type) was switched on between 1300 and 1500hrs. I was pleasantly surprised it didn't horrendously effect the voltage (via loops etc). It is on the same run/phase from the distribution board. The room warmed up from about 21 to 27C by 1300 then cooled to about 21 by the aircon. The 3458s internal temperature reflected this and I suspect probably also so did the references temp but the voltage of the MAX166 only indicated an internal temp change of the reference by about 2 or 3 degrees ( I forgot to write the result down ).
The top is a scattergram of the 3458 self measured Internal temp vs measured voltage of LTZ reference. To me it probably shows both the 3458 and the external LTZ1000s temp coefficient - poss other effects e.g. lead to terminal thermal gradients. etc. Hysteresis I think is also evident. Overall reasonably happy with 8uV / 7V  over 5C temp change so about 0.2ppm/C which I think is in spec - mine is a very old 3458. SN 28*******
Robert

[enut11]

Thanks for the update @VK5RC. It all goes to show that when you venture beyond 6 digits all manner of influences can affect the readings. So it is important to talk about it so that we can learn and improve our measurement skills.

Even with a 6.5 digit dmm I am not certain of the true origins of the fluctuations that I see in my home made Lm399 voltage refs. Consequently I am hoping that the next step, an LTZ1000 REF, will clarify the situation.

Now that the Aussie Cal Club is up and running, we will soon be in a position to exchange cal data which I believe is an important step in estabishing confidence in our DMMs.
Enut11

[VK5RC]

Hi enut11, 
The more you look the more you see (or don't want to see). It does get very confusing. I am now pretty sure just switching on my laptop about 50cm away from the reference and the 3458 alters the reading by around 3-4uV. Connecting it (with Prologix) and connecting its power supply also add a lesser but not trivial voltage 'errors' .
Arrrrggggghhhh.
Robert

[VK5RC]

Just an update, the "Aussie Cal Club" has completed its first round - below is an action shot of testing one of the last references in Round1.
My desk is usually that messy!
Next photo is the references boxed up heading back to New South Wales from my state of South Australia.

I am not sure what to fully conclude from the first round.
One member has an 'in calibration Fluke 7 1/2" - this is very likely to give the best results but the methodology of warming up. what power supply, what is switched on in the room, what cables are used, and what temperature it is inside the reference are some of the issues that will be being looked at in Round2.

My 3458 definitely reads high on DC V (prob about 3ppm) but is pretty consistent, my ability to get repeatable ohms readings out of it definitely need improvement.
A 34461 has done quite well, esp for the price.
Robert

[TiN]

Maybe you want to wait till LTZ get back to you?
High chances you'd get it by end of the may...

[VK5RC]

Hi TiN,
No rush re getting the reference back,  I have another three LTZ based references (and a Fluke 731b), one LTZ  is on an HP board the other two are your KXs design, one of the KXs has gone for round 2 around Australia - its the same as the one you have with Edwin's resistors but I can't seem to get its temp sensor to work!!!
Regards Rob
PS When the reference you have does comes back , I will have play with it for a short while then I might get it to go around and get the fellow with the new Fluke to liaise with you.
Rob

[bitseeker]

Just an update, the "Aussie Cal Club" has completed its first round - below is an action shot of testing one of the last references in Round1.
My desk is usually that messy!
Next photo is the references boxed up heading back to New South Wales from my state of South Australia.

Congrats, Aussie Cal Club. Rob, I just had to mention that I like your alligator/croc clip storage method. I'll have to give that a try. Otherwise, they tend to wander off.

[enut11]

Hi VK5RC. Love the pic of your lab. I am currently set up in a shared computer room and under strict orders to keep it tidy! In a way its good because it forces me to clean up after every session.

I am currently analysing the data from Round #1. 5 members took part, mostly junior voltnuts. We shared voltage, resistance and current standards. Although we did not adhere to strict metrology methodology there was still a lot of useful data gathered. Already I have a lot more confidence in my old uncalibrated HP3456A.

Round #2 will be better with a number of LTZ1000 and LM399 refs as well as better resistance refs. We are also looking to standardise our measurement techniques.
Enut11

[TiN]

Hopefully all the data will be published, so we all can learn and enjoy the ride 

[VK5RC]

enut11 is  the driving force behind the group, Thanks Lou,  TiNs work continues to inspire 

The funniest part of my setup is the old sheet on the chair - it has a hole in the middle (for your head)  so if I feel the need to do a bit of soldering or spray painting and I can't be bothered to get out of work clothes.........
Rob

[bitseeker]

Rob's lab trivia.

[cellularmitosis]

Just wanted to say I'd love to be in on the next round!  I can send out a Gellar Labs reference, as well as a Pentaref, if that's considered stable enough to be useful.  On my end I have an HP 3478A (5.5-digit) and Keithley 196 (6.5-digit), both of which are uncalibrated.  I'm also working on a LM399 design but haven't aged my 399's yet.

[enut11]

Hi cellularmitosis. I presume you are talking about a USA Cal Club. I suggest you PM other Forum members from USA/Canada who have posted on this thread and see what you can arrange between yourselves. This way you can get things moving quickly without the complexities of international shipping.
enut11

[julianhigginson]

I'd love to get in on the Australian club... How does someone new apply?

[enut11]

I'd love to get in on the Australian club... How does someone new apply?

PM me. Tell me where you live and what equipment you have, both meters and standards (if any).
enut11

[bitseeker]

Just wanted to say I'd love to be in on the next round!  I can send out a Gellar Labs reference, as well as a Pentaref, if that's considered stable enough to be useful.

Hi cellularmitosis. Which model is the Geller Labs reference and to what resolution is the calibration data? I wasn't sure from the info on their retired product page to what extent it can be used as a transfer standard.

The Pentaref data is to four decimal places, so I surmise it'd be OK to check a 3.5- or 4.5-digit DMM against. I'm sure others here can provide more experienced guidance.

I'd be interested in participating with the various meters I have (up to 6.5 digits), but I don't have the expertise to run a cal program for this region like there now is for Aus/NZ.

[julianhigginson]

PM me. Tell me where you live and what equipment you have, both meters and standards (if any).
enut11

done!

[BradC]

I'd be interested in participating with the various meters I have (up to 6.5 digits), but I don't have the expertise to run a cal program for this region like there now is for Aus/NZ.

Now, now. Don't go mistaking our enthusiasm for expertise!

[enut11]

PM me. Tell me where you live and what equipment you have, both meters and standards (if any).
enut11

done!

Hi julianhigginson.

Welcome to the Aussie Cal Club. An enthusiastic group of (6 now) junior voltnuts. We are in the throws of starting another roving standards session where we each commit one or more voltage/resistance/current standards to travel around the country. This is a good time to join.

I will PM you with more info.
enut11

[bitseeker]

I'd be interested in participating with the various meters I have (up to 6.5 digits), but I don't have the expertise to run a cal program for this region like there now is for Aus/NZ.

Now, now. Don't go mistaking our enthusiasm for expertise!

LOL! Well, I figured I'd err on the side of compliments.

[Ash]

I've just noticed that there is an Aussie Cal club. (I've only really been active on the forum for the last month I guess). 

I'd love to get involved as well. @enut11, Do I just PM you my details?

I've got a Keithley 2015, and will have 2 Keithley 196s soon (all 6.5 digit). Nothing in cal, but all should have good well aged references to compare against.

I do also have an EDC 521 voltage calibrator that I fixed, but I don't trust that it is anywhere near in cal, but it would be a good baseline to compare against I guess. I was planning on constantly tracking it against all the Keithleys to get some relative drift confidence.

I also have a matrix switch coming and I was planning to design and build some "simple" zener references (a little ways off yet) and use this gear the track them all against each other. I use Prologix Ethernet GPIB interface and can write code to drive it all.

If there is anyone in the Brisbane area with access to a calibrated 6.5+ meter, I'd like to adjust my EDC voltage standard if that would be possible??

Thanks,
Ash.

[IconicPCB]

Hello Ash,

I am in Brisbane  too but unfortunately all I can offer is a well calibrated wit.
Glad to see You are a local lad, may be some day we can exchange salty tales and cross reference the reference.

PS I too am expecting some of the chinese zeners to land on my door step any day now. I would like to try them out in a slightly different configuration to what’s been done so far.

[Ash]

I am in Brisbane  too but unfortunately all I can offer is a well calibrated wit.

  Perhaps that will be useful 

Glad to see You are a local lad, may be some day we can exchange salty tales and cross reference the reference.

PS I too am expecting some of the chinese zeners to land on my door step any day now. I would like to try them out in a slightly different configuration to what’s been done so far.

Sounds good. I've not got involved in the Chinese Zeners yet (tempted) but I was going to first of all try to do something with some 1N829A like in my calibrator. I was also going to play around with some others as well. But first I have to get my K196s and switch matrix up and running with some software support so I can monitor them against my calibrator to see how things behave.

PM me if you want to have a chat one day.
Ash.

[technix]

PS I too am expecting some of the chinese zeners to land on my door step any day now. I would like to try them out in a slightly different configuration to what’s been done so far.

I have placed the order to the factory. There will be some leading time as their own stock is running low (someone placed a GINORMOUS order in the aggregation.)

Are those diodes really that good a reference? I am still deciding between that 2DW23x and LM399 for my own calibrated voltage transfer standard. There are government-operated cal labs in Shanghai that is two or three steps away in tracing from the global standard.

[VK5RC]

Hi Guys, re Aussie Cal Club, there is a group of 5 or so (I am one) who have done one round - each contributing a voltage reference and or resistor reference - measuring then forwarding results and the references to the next person. Round two has just begun. One of the guys has an 'in Cal' 7 1/2 digit meter but if I can summarise a very complex situation - when you get below 10s of uV (out of a 7-10V reference) almost EVERYTHING counts. I think our first round has showed that. Temperature, humidity, warm up, on time, EMF interference from anything etc - the list goes on.
enut11 is probably the main contact and if he doesn't see this shortly I would PM him. 

[Ash]

Hi Guys, re Aussie Cal Club, there is a group of 5 or so (I am one) who have done one round - each contributing a voltage reference and or resistor reference - measuring then forwarding results and the references to the next person. Round two has just begun. One of the guys has an 'in Cal' 7 1/2 digit meter but if I can summarise a very complex situation - when you get below 10s of uV (out of a 7-10V reference) almost EVERYTHING counts. I think our first round has showed that. Temperature, humidity, warm up, on time, EMF interference from anything etc - the list goes on.
enut11 is probably the main contact and if he doesn't see this shortly I would PM him. 

Hi VK5RC, I'm keen to get involved so I can get a chance to develop my knowledge and skills in this area more. It wouldn't be fun if it was easy

I may not be ready for the next round as I still have to get my equipment and set it all up and get some confidence in it before I would feel like I can be of use. Might take me a month or two to get at least a little organised. So I'm not sure how that fits in with the next round.

I will be trying to build some sort of references and I was also putting together a resistance box as well for myself. Again, the initial cal is the trick

[VK5RC]

Hi Ash,
Hopefully enut11 will read this soon, don't get the idea we are experts, esp me!
There are some very serious guys like DrFrank, CalMachine and TiN whose posts are good value.

I am still trying to get consistent readings - which is very hard - I have an old 'out of cal' 3458 with dodgy ACV and with 4 hours warm up of the 3458 and my Fluke 731b reference, with no lights on in the room, no other electrical devices on other than my laptop with a GPIB interface I am getting readings reasonable repeatable to 3-5uV or so (holding my tongue at the right angle) ......mostly       

In the current round, one of my LTZ1000 Kx references is going around Australia, one has gone for a trip to Taiwan (thanks TiN) and upon return I think it too may go for an Aussie round. The rounds are actually quite slow as measuring each reference takes a lot of time, for most of us its after hours work- a round could easily take 3-4 months - so no rush.

73 Robert

[Ash]

I am still trying to get consistent readings - which is very hard - I have an old 'out of cal' 3458 with dodgy ACV and with 4 hours warm up of the 3458 and my Fluke 731b reference, with no lights on in the room, no other electrical devices on other than my laptop with a GPIB interface I am getting readings reasonable repeatable to 3-5uV or so (holding my tongue at the right angle) ......mostly       

In the current round, one of my LTZ1000 Kx references is going around Australia, one has gone for a trip to Taiwan (thanks TiN) and upon return I think it too may go for an Aussie round. The rounds are actually quite slow as measuring each reference takes a lot of time, for most of us its after hours work- a round could easily take 3-4 months - so no rush.

I certainly don't know much. I've been trawling through the metrology area picking up what I can from the 'serious' guys. Fascinating stuff. This analogue precision stuff is way new to me (I'm a digital / firmware / software guy) so I decided to take a leap and learn something new and interesting.

I too would be doing this in the evenings, but I do work from home so I'm thinking that I want to get it all automated so it can tick away in the background and make lots of measurements and I can keep an eye on it. But first I need to prove out my setup. I'm 'only' doing 6.5 digits for now - dip my toes in as it were.

Probably all started when I bought my HP8595A specky, then a Keithley 2015 THD. Then the test gear bug bit...  So of course I can't tell anything with just 1 meter, so I found an eBay seller with a Keithley 196.. and they had 2 of them - perfect I also had acquired my EDC 521 voltage reference that I've just fixed. so I was going to start using all three meters (well, when I'm not using the 2015 for real work) to monitor the voltage reference. Then I can get some idea of relative drift. Then I found a Keithley matrix switch for next to nothing (actually 2 of them...)    oh dear.. how deep does the rabbit hole go?? 

I think I need to go check into Test Equipment Anonymous now.. 

Ash

[TiN]

how deep does the rabbit hole go??

It goes deep. Very deep. I wouldn't call myself serious by any analogue means, I just have 4 8.5-digit meters, but that means nothing good.

one has gone for a trip to Taiwan (thanks TiN) and upon return

Hear, hear... I'd better get it modified, retested and send back.

One thing I'd like to see, is bit of more transparency for outsiders of Oz club. Meaning to see actual datalogs/charts/excels/plots whatever has you, with accepted level of obfuscation (like addresses, IDs, shipping info, etc ).

[enut11]

Hi Ash. Currently in Qld. Will be back in NSW by Fri. PM me with your email address and I will get back to you. We recommend starting with an LM399 for your first Vref. One of our members can supply a pcb.
enut11

[Ash]

how deep does the rabbit hole go??

It goes deep. Very deep. I wouldn't call myself serious by any analogue means, I just have 4 8.5-digit meters, but that means nothing good.

 

Maybe one day I'll have enough gear...  doubt it.. 

[Ash]

Hi Ash. Currently in Qld. Will be back in NSW by Fri. PM me with your email address and I will get back to you. We recommend starting with an LM399 for your first Vref. One of our members can supply a pcb.
enut11

Thanks will do that.

[enut11]

how deep does the rabbit hole go??

It goes deep. Very deep. I wouldn't call myself serious by any analogue means, I just have 4 8.5-digit meters, but that means nothing good.

one has gone for a trip to Taiwan (thanks TiN) and upon return

Hear, hear... I'd better get it modified, retested and send back.

One thing I'd like to see, is bit of more transparency for outsiders of Oz club. Meaning to see actual datalogs/charts/excels/plots whatever has you, with accepted level of obfuscation (like addresses, IDs, shipping info, etc ).

Hi TiN. We inderstand the importance of sharing experimental data. As we are just starting out we only have a spreadsheet of single measurements for each ref from each member/meter. Not sure if it would be of much interest to others. Perhaps when we start graphing longer term data this will change. However, am open to suggestions on how to improve feedback.
enut11

[TiN]

Hi TiN. We inderstand the importance of sharing experimental data. As we are just starting out we only have a spreadsheet of single measurements for each ref from each member/meter. Not sure if it would be of much interest to others. Perhaps when we start graphing longer term data this will change. However, am open to suggestions on how to improve feedback.
enut11

It's not the data itself that may be value for the others (including new followers, which may be considering to jump in) but how are the transfers done, and how everything is roving. Sure, more data from automated datalogging setups (VK5RC will be getting configured Pi3 to sample data, etc.) is great to have, but more importantly is knowledge what can be obtained, how one can contribute, and what a reference anchors of the whole club.

And I see LOT of hidden titanic-grade icebergs in these murky waters here, so sharing details of _how_ things are going and done, already higher value than the calibration points data itself. Ideally would be great if someone would take a time and write-up a guide or an article, covering the procedure, going down to cable types, shipping hints, instrument settings (e.g. measuring 10Kohm resistance by even HP 3458A without offset compensation delays (seconds) may easily cause 20+ppm errors, as Dr.Frank demoed while ago. This documented, but very not obvious important detail, which entry-level volt-nuts may not know about). I sorta tried to do such article/notelog for a first DCV transfer I made last year.

If you need site hosting, web storage space for such data/experiment setup logs, I'm happy to provide.

[enut11]

Aussie Cal Club - the story so far...

TiN puts up a compelling argument, so here goes. I initially started this thread because I had just purchased my first true DMM, an out-of-cal HP3456A 6.5 digit.
Even though it is a monster in size, and takes up a disproportionate amount of my very limited desk space, I have become quite attached to it.

After some minor repairs, with the help of EEVblog Forum members, I needed (wanted) to find out how accurate this old meter was (first bite of the voltnut bug). My initial idea was to band together with 10 other like-minded souls and fund the professional calibration of the best meter in the group (hopefully a HP3458A) and use that to calibrate all the other member's meters. Well, this idea quickly died but what did come out of this was an interest in sharing home made and professional standards.

The practicalities of international shipping were discussed but I wanted to start out with a local club first to see how it would work (I see there is now a USA Cal Club starting up).

We started with 4 Australian members (now up to 7 Aussies), mostly junior voltnuts with 1 senior nut. Only two members had in-cal meters, 6.5d and 7.5d. All had the same question "How accurate is my gear?".

We started out by each member sending his Refs to a nominated member so that all Refs could be measured at the same time and place. All data was informal in the sense that we did not have a set of instructions on how to go about it. Also, conditions, mainly temperature and humidity, were not constant. Our members are scattered across the country and summer here can get quite hot and humid.

We discovered the importance of equipment and reference warm-up times, the effect of ambient temperature and air currents, effects of nearby electronic equipment, single measurements vs statistical averaging, etc.

Despite the difficulty in navigating through this minefield, we did end up with some valuable data for Stage #1.

More to come
enut11

[bitseeker]

My initial idea was to band together with 10 other like-minded souls and fund the professional calibration of the best meter in the group (hopefully a HP3458A) and use that to calibrate all the other member's meters. Well, this idea quickly died but what did come out if this was an interest in sharing home made and professional standards.

The practicalities of international shipping were discussed but I wanted to start out with a local club first to see how it would work (I see there is now a USA Cal Club starting up).

Yes, thanks to the inspiration from this thread, a US-local one has started up.

Since the focus of this thread has become regional, do you want to adjust the subject accordingly?

[enut11]

My initial idea was to band together with 10 other like-minded souls and fund the professional calibration of the best meter in the group (hopefully a HP3458A) and use that to calibrate all the other member's meters. Well, this idea quickly died but what did come out if this was an interest in sharing home made and professional standards.

The practicalities of international shipping were discussed but I wanted to start out with a local club first to see how it would work (I see there is now a USA Cal Club starting up).

Yes, thanks to the inspiration from this thread, a US-local one has started up.

Since the focus of this thread has become regional, do you want to adjust the subject accordingly?

Hi @bitseeker. I believe not as it may inspire other regions or countries to start their own Cal Cub. Also, as TiN has indicated more than once, shared information is vital for the growth of knowledge. Without a forum such as this I would be on my own and would probably give up. Metrology may be simple but it is certainly not easy.
enut11

[GigaJoe]

is any Canadian around ?

[bitseeker]

Hi @bitseeker. I believe not as it may inspire other regions or countries to start their own Cal Cub.

Ah, yes.

[0.01C]

I hope there is a similar calibration club in Hong Kong.

[lowimpedance]

@ 0.01C .........Whoa, the equipment listed in you sig. gear you actually have ??  .............or would 'like' to 

@ enut, any luck with the 335 ?.

[enut11]

Hi @lowimpedance.
Back from Cairns but soon away again. Managed to check one of the PCBs. The others will have to wait until we get back from GC.

[TiN]

I hope there is a similar calibration club in Hong Kong.

If sig gear is yours, you are more looking at starting your calibration club in HK . I wouldn't mind to hop to HK from Taipei for some few-day holiday to play with some gear and talk about things

[0.01C]

@lowimpedance @TiN All these toys are in my home, but only SR104 has been calibrated.
I'm interested in collecting resistor.

[CalMachine]

@lowimpedance @TiN All these toys are in my home, but only SR104 has been calibrated.
I'm interested in collecting resistor.

Dat 8508 Doe...      

[HighVoltage]

@lowimpedance @TiN All these toys are in my home, but only SR104 has been calibrated.
I'm interested in collecting resistor.

You have an impressive collection at your home.
What brand cable do you have between the 732A and the 3458A?

[TiN]

That is Pomona 1756.

[HighVoltage]

Thanks, found it, datatsheet attached

[enut11]

Aussie Cal Club - the story so far...

TiN puts up a compelling argument, so here goes. I initially started this thread because I had just purchased my first true DMM, an out-of-cal HP3456A 6.5 digit.
Even though it is a monster in size, and takes up a disproportionate amount of my very limited desk space, I have become quite attached to it.

After some minor repairs, with the help of EEVblog Forum members, I needed (wanted) to find out how accurate this old meter was (first bite of the voltnut bug). My initial idea was to band together with 10 other like-minded souls and fund the professional calibration of the best meter in the group (hopefully a HP3458A) and use that to calibrate all the other member's meters. Well, this idea quickly died but what did come out of this was an interest in sharing home made and professional standards.

The practicalities of international shipping were discussed but I wanted to start out with a local club first to see how it would work (I see there is now a USA Cal Club starting up).

We started with 4 Australian members (now up to 7 Aussies), mostly junior voltnuts with 1 senior nut. Only two members had in-cal meters, 6.5d and 7.5d. All had the same question "How accurate is my gear?".

We started out by each member sending his Refs to a nominated member so that all Refs could be measured at the same time and place. All data was informal in the sense that we did not have a set of instructions on how to go about it. Also, conditions, mainly temperature and humidity, were not constant. Our members are scattered across the country and summer here can get quite hot and humid.

We discovered the importance of equipment and reference warm-up times, the effect of ambient temperature and air currents, effects of nearby electronic equipment, single measurements vs statistical averaging, etc.

Despite the difficulty in navigating through this minefield, we did end up with some valuable data for Stage #1.

More to come
enut11

Aussie Cal Club Continued...

A number of interested Australians connected via this thread:

Members Meters:
Tek 7510 (7.5d DMM, in cal)
3 Keysight 34461A (6.5d DMM, in cal)
HP3458A (8.5d DMM, out of cal)
HP3457A (6.5d DMM, out of cal)
HP3456A (6.5d DMM, out of cal)
HP34401A (6.5d DMM, out of cal)
Keithley 2015 (6.5d DMM, out of cal)
Keithley 2700 (6.5d DMM, out of cal)
2 Keithley 196 (6.5d DMM, out of cal)

Members References:
DMM Check+ multi ref
AD588 10v
AD587 10v
LT1236ACN8-10 — 10V ± 0.05%, 2ppm/ºC
MAX6350CPA+ — 5V ± 0.02%, 0.5ppm/ºC
LT1019ACN8-2.5 — 2.5V ± 0.05%, 3ppm/ºC
Y145310K0000V9L — 10k? ± 0.005%, 0.2ppm/ºC
Y07851K00000T9L — 1k? ± 0.01%, 2ppm/ºC
LM399 C3 (unboxed)
Calibratory 10.000000 VDC ±0.0002% (±2ppm)

Resistors
Vishay Metal Foil
Foil Resistor 100K
Foil Resistor 10K
Foil Resistor 1K
Foil Resistor 100 Ohm
Foil Resistor 1K14 Ohm

All the above Refs were sent to one member who set about measuring them under the same conditions. Initial temp and humidity were noted and all results were recorded in a spreadsheet. Some were simple 1-off readings after equipment and refs were allowed to stabilise, often up 24 hrs. Those who could took advantage of statistical averaging.

All Refs were then shipped in bulk to the next member who repeated the process. As this was our first attempt we made a few errors, mainly in environmental management. It was summer time in Australia and coastal towns can get hot and humid. Most members did not have a temperature controlled workshop and we all know temp is king when it comes to high resolution voltage measurements. Also, EMF radiation (fluro lights, computers, etc) proved a challenge for those chasing more than 7 digits!

Despite all the problems we ended up with a set of very consistent results. Members with out-of-cal equipment were able to see how their DMM compared with the calibrated units.

Some of us have already started to build better refs to play with. Initially LM399s and now LTZ1000s, all inspired by the Metrology section of the EEVblog Forum. These  new refs are in soak mode to attempt to stabilise the output. We are also looking at rationalising our methods of measurement to improve uncertainty.

The journey continues...
enut11

PS
We have just had two new members join recently and are now 7 strong.

[0.01C]

@lowimpedance @TiN All these toys are in my home, but only SR104 has been calibrated.
I'm interested in collecting resistor.

You have an impressive collection at your home.
What brand cable do you have between the 732A and the 3458A?

That pomona is not so good , use teflon silver plated four wire shielded cable and copper spade lug DIY is better and cheap ,teflon cable $2-3/M, spade lug $30-40/1000pcs

[enut11]

Hi @0.01C
Where did you buy the pure copper spade lugs?
enut11

[0.01C]

Hi @0.01C
Where did you buy the pure copper spade lugs?
enut11

I bought from taobao.com , ¥16 100pcs
If you want ,I can send you some .

[enut11]

Hi @0.01C
I went to taobao.com but could not see how to change the web-page to English. Can you sell me some copper lugs or buy some on my behalf? PM me if interested.
enut11

[0.01C]

Hi @0.01C
I went to taobao.com but could not see how to change the web-page to English. Can you sell me some copper lugs or buy some on my behalf? PM me if interested.
enut11

Sure ,I can send you some for free ,pm me

[TiN]

I'd like few too. Checking with some factory to make copper banana jacks too, still in progress to get quotation.

[0.01C]

I'd like few too. Checking with some factory to make copper banana jacks too, still in progress to get quotation.

no problem , pm me,
I think banana jacks is not good for low thermal .
taobao diy binding post @$3.5

[Vgkid]

taobao diy binding post @$3.5

Can you give us some links, please.
Thanks.

[TiN]

I agree, banana is a PITA to use for high precision stuff, but I'm not ready yet to modify my Keithley 2002's for binding posts

[SvanGool]

I would also be very interested in copper lugs, binding posts and banana plugs. FYI I now submit tinned copper items to DIY electrolysis and that works, for certain brands (some use another plating process) but it is a tedious process.

[Ash]

no problem , pm me,
I think banana jacks is not good for low thermal .
taobao diy binding post @$3.5

Those look good. I'd be keen to purchase some of those and the copper lugs as well. I've several projects coming up that I'd use the copper binding posts on and they look perfect.

If you could provide links that would be cool! Or if you wanted to run a group buy I'd be happy to be involved.

Thanks heaps.
Ash.

[VK5RC]

I agree, banana is a PITA to use for high precision stuff, but I'm not ready yet to modify my Keithley 2002's for binding posts

I have a similar opinion re a 34461.
A while ago I made a pair of lug to banana adapters (bodge city! - soldered)  and did a run with an ltz1000, with either the adapters in or out of the circuit, (main lead was Pomona low emf banana pair lead)
No difference detected with about 500 measurements in each run but constant temperature .
PS Aus Cal guys - the adapters are coming around with the ltz1000.
Robert
Edit   corrected model number

[0.01C]

no problem , pm me,
I think banana jacks is not good for low thermal .
taobao diy binding post @$3.5

Those look good. I'd be keen to purchase some of those and the copper lugs as well. I've several projects coming up that I'd use the copper binding posts on and they look perfect.

If you could provide links that would be cool! Or if you wanted to run a group buy I'd be happy to be involved.

Thanks heaps.
Ash.

here  https://world.taobao.com/item/40823926055.htm?fromSite=main&_u=g1paopr9dbf

[Ash]

here  https://world.taobao.com/item/40823926055.htm?fromSite=main&_u=g1paopr9dbf

Ok, first time I've used Taobao and had to rely on Google Translate. 

Hoping it works out! 

Thanks for the link!

Ash.

[0.01C]

here  https://world.taobao.com/item/40823926055.htm?fromSite=main&_u=g1paopr9dbf

Ok, first time I've used Taobao and had to rely on Google Translate. 

Hoping it works out! 

Thanks for the link!

Ash.

I just contact the binding posts seller , his email is qinchang001@sohu.com   ,if you have question ,you can contact him.

ps : I don't know the seller and bought from him only once.

[SvanGool]

I looked at Tao Bao to purchase 10 pieces but I am getting 240 Yuan shipping cost to Europe, which is about 32 Euro.

[0.01C]

I looked at Tao Bao to purchase 10 pieces but I am getting 240 Yuan shipping cost to Europe, which is about 32 Euro.

10pcs is about 100g ,ship from HK POST to Italy is about HKD40.

[SvanGool]

That would be indeed much better shipping cost (app. 4.57 Euro), now we need to convince the seller/Taobao 
Taobao recommends to contact the seller about the shipping cost, I did, no reply yet.

(Meanwhile we are polluting this thread from message msg1234742 on, maybe a moderator can move this to a new "Low thermal-EMF materials" thread)

[VK5RC]

With thanks to TiN and I believe SvanGool for putting design up on OshPark, and Lou et al for the Aus Cal Club 

A set of 6+ LTZ references being slowly built- aim is long term  - kept ON  - in a controlled temp cabinet, measured every 3 months or so - watch their drift (and that of my 3458 and 34461).
Difficult part will be getting lab at a constant temp without too much interference from heating-cooling system- I don't have a cellar - but tempted to dig a big pit!
I will probably heat / cool lab for 48hrs prior to measure time - then switch off.  I have also seen a little interference from the computer +/- PSU  / GPIB interface. Lots of known (and avoidable) interference from LED lights and other SWPSUs.
Most (5)  will be with TE UPS50 resistors, closest I can easily get to 13k is 13.3k (paralleled 20k and 40k), 70k (20k+50k), I have one set of Mr Pettis' left.
Four will be with LT1006 and 100nF across 1k and 120R, but two LT2057s
Four  will be with LTZ1000As but a generous Aussie gave an LTZ1000C and I have one 'C' of my own.
It won't be a quick result project!
Robert
VK5RC

[bitseeker]

A cellar would be a nice thing to have for relatively constant temp. The humidity might not be ideal, depending on where you're located. Underground/cave lab in the middle of the desert.

[GFWD1D]

Hi I'm new to this forum and would like to know more about your building of V refs.

I'm also interested in the calibration forum that has been set up here in ADL or Aust.
 

[enut11]

Hi GFWD1D
Please tell me a bit about yourself wrt electronics, professional or hobbyist?
Also what type of equipment do you own and what State/town do you live in.
What do want to achieve wrt Vrefs?
Please send your reply via Personal Messages.
Regards
enut11

[enut11]

Hi I'm new to this forum and would like to know more about your building of V refs.

I'm also interested in the calibration forum that has been set up here in ADL or Aust.

Hi GFWD1D. A good way to start out in Metrology with Vrefs is to build an LM399 based reference. Parts are easy to get and not expensive. PCBs are available from one of our Aussie Cal Club members.
Use a plastic or metal box (better shielding) and download the LM399 spec sheet. This circuit is based on the 'portable calibrator' from the spec sheet. You can power it from a regulated 15v supply (not switch-mode, too noisy) or from a battery (lower noise). Circuit draws about 25mA. The 3 output terminals provide Vz and 10v.
enut11

[VK5RC]

Hi Aus Cal Guys et al.

Sometimes out of a stuff up comes some good. My LTZ references (almost all Kx - Thanks again Ilya) have been sitting in a shelf as part of a longer term experiment- mostly happy - I moved some other test gear a week or so ago and didn't noticed the pile of stuff had moved and pulled out the DC connectors!

I thought it would be good to put it all in a steel enclosure I had spare. It started to grow a bit as a project . I have a linear mains to 18V DC supply which can been seen outside the box in the photo below - labelled PSU1.
The DC is transferred in some shielded twin cable - directly into a small common mode filter box "Filter". Consists of about 2x14 turns (counter-wound) on a ferrite core and a small 100nF cap between the DC rails. The shield is connected to the box - not mains earth. 18V is distributed to secondary low noise linear PSUs, based upon TPS7A4700 - down to 15V for the KX labelled PSU2.

Today quite a bit of time was spent grinding off paint and checking continuity between the panels, rails etc. Common tie point to the shields.
Inside references were well fixed (my favourite 'bodge' attachment method) using double sided sticky tape and zip ties.

Previously I have had some interference from SMPSUs in my DC measurements esp my LED downlights - often in the order of 10-30uV! Today following the 'boxing' it is down to around 1-2uV.

Edit ; grammar.

[beanflying]

Bump 

Collected most of the bits I need. Ali box for the Vishay .005% arriving next week.

Plan is two socketed Max 6350 CPA references powered by 3S LiPo's in the small Ali enclosures with charge and cut out boards (shielded from the reference as well as space allows)

Vishays 2 x 10k, 1x 5k, 2x500R and a 100R mounted as 4W independent resistors so they can be used as a precision divider set. Allows 1-10V in 1Vsteps and 0-5 at .5V or 1-20mA precision currents plus others which suits the accurate temperature logging projects I am working on. Considering adding an additional 2 resistors to this lot yet to generate a few more steps.

Seemingly very accurate Agilent 34401A (2 years out of Cal from a clean room environment)

Might mount the lot into a larger temp stable enclosure at some stage but 3 units suits my limited bench space.

So consider me interested in a swap of some sort in the New Year if it comes up again.

[enut11]

Hi @beanflying
Let us know when you are ready to compare your Ref measurements with ours. We have several DMMs with 6-8 digits.
enut11

PS
I am also into R/C flying. Where do you live?

[beanflying]

SW Victoria in Koroit / Port Fairy area.

Breadboarded one of the Max's this morning. Horrible thing 4.99997V I blame the Temperature it's only 23 degrees

On for 30 minutes now. Top of the chip is 27 degrees and 5.00001V

[enut11]

Hi @beanflying
Long way from me. I am on the east coast just south of Sydney.

Temperature is king when it comes to Vrefs. Open refs respond to air currents and other influences. Try a metal box with insulation. One of our members has been working on a Vref oven with control down to -/+0.1C
enut11

[beanflying]

If you have ever flown competitive Gliders or Electrics we would know some of the same mob 

Should have them in the little Deltron enclosures today or tomorrow to start burning in. 480mA will run over a week while I get the charging boards built.

[beanflying]

Quick question on enclosures. Did I read correctly somewhere to leave the gaskets out? Need to know how much space I don't have left 

The posts are gold (chinese  ) plated brass, brass washers and some brass knurl nuts I have sliced in two to hold the board. The posts will still be soldered to the output of the reference rather than using the brass to copper junctions. Basically removing any iron from the output path I can easily was the plan.

Breadboard hack up got up to 5.00003 and as it cools a touch sitting at 5.00002.

[BradC]

Breadboard hack up got up to 5.00003 and as it cools a touch sitting at 5.00002.

How much has your room temperature fluctuated? How much of that drift is the ref and how much is your meter?

[beanflying]

The great unknown 

Over the afternoon raised by about 8 from this morning when I first hooked up but it jumped quickly after 30 minutes settling. Top of the chip is now at 24.5 degrees and reading 4.999998. Based on bulk I am sure whatever the Meter is drifting it will lag behind the exposed IC.

The bits will be in a box in a couple of hours, still have room to cram a charging and monitoring board and an RTD next to the chip over the next week.

edit: Just dropped the second 6350 on the bread board running at 4.99982 as the temperature drops to about 17C

[Andreas]

Hello,

my 2 MAX6350 samples drift around 10 ppm/year.
So compared to many of my AD586LQ (after 6 months run in time) this is around factor 5 more.

with best regards

Andreas

[beanflying]

Mmmm I have a 3rd enclosure too 

More bits for my next Mouser order ............

[TiN]

I would avoid lithium packs due to shipping restrictions .

[beanflying]

Internal shipping on small LiPos by road post is fine https://www.master-instruments.com.au/files/product_warranty/customer_guidelines_for_lithium_batteries.pdf.pdf

Most Freight companies in Australia have a dangerous goods area or shipping option too.

LiPo's can be shipped by air but there is plenty of hoops to jump through so not worth the effort for this sort of thing. We have shipped multiple dozens of 6S 5000mAh batteries for model aircraft use internationally.

Generally LiPos get shipped by post without the declarations on the parcel anyway 

Part of the reason to maximise the LiPo in the enclosure was to allow it a 7-8 day unplugged life to allow for moving around powered up.

[beanflying]

Now 28 degrees and it has flicked up to 01.

Still some bits to add in the box. Will be adding the trimpot but it will have an external jumper to add it or not.

[beanflying]

So now I am officially broke but the owner of two 34970a's and 4 modules. 

Get in quick these are a steal thanks to Toyota pulling out of the local car industry https://www.ebay.com.au/itm/Agilent-34970a-Data-Acquisition-Switch-Plus-2x-modules/173019637414?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

Drop Rohan a message tell him Tim sent you and ask about the 1 and 2m GPIB cables. There was initially 34901a, 34903a and 34907a modules available. He will pack and post items.

Also some Power Supplies listed and Sig Gens coming up but I am out of pocket money .........

[mimmus78]

Beware of those fake copper transparent binding posts ... I get a couple of them few months ago and if you cut in half you'll find they are not copper.

[beanflying]

Fairly comfortable they are Brass based on some filing and magnetic response. The Nuts, washers and soldering washers were certainly iron based on the couple of different ones I got in so I junked them in favour of plain brass and silver based solder. For their 3 and 4 1/2 digit testing job I wasn't to worried about emf precision.

[VK5RC]

I have not been completely volt-nut lazy over the past few months but doing a bit of an experiment - mainly to help me understand voltage references - in both long term drift , temperature and construction of Voltage references. The basis has been TiNs Kx board - again thanks Ilya for sharing your efforts. The reference that TiN evaluated is No 2.
I have 11 voltage references , 10 of which have been powered on continuously since the experiment started in August 2017 (UPS). All Kx have a 2 stage linear regulation power supply, 1st to 18V then to 15V.
Each reference is slightly different - by accident initially - but then expanded.  Below is a table of their differences

Ref No    LTZ Version   Kx Board version   OpAmp    Resistor type      Temp Resistor
   1                 A           early                    2057      Vishay z202s             12k       
   2                 A           early                    2057          Pettis                    12k
   3                 A         early modified         2057         Pettis                     12k
   4                 A              later                  2057     120 Vish, TE-UPW      13.3K
   5                 C              later                  1006         TE-UPW                 13.3k
   6                 C             later                   1006          TE-UPW                13.3k
   7                 A             later                   1006          TE-UPW                13.3k
   8                 A             later                   1006      120Vish, TE-UPW       13.3k        Vish S102
   9                 A             later                   1006      Pettis120, TE-UPW     13.3
 3458    A 3458s LTZ reference board
Fluke 731b
The boxing/insulation of 4 to 9 are identical.
The set up for each measurement has been similar, 3458 ( a very old one) on for 12 hrs before, room temp >17 for 4 hrs before, heaters/lights off during measurement, DC ACAL, NPLC 100, the same low EMF (Pomona) cables used. Cables left connected for 5 mins before reading taken - draft cover on.

I was a little surprised with the longer term stability  of the measurements, I thought I would see more drift, I suppose I am trying to measure "one ruler with 9 very similar rulers" - I can't get around that short of a JJA ! My findings seem to support the comments of some of the more experienced of you do seem to get some "golden" LTZ - some seem to be doing better.
 -
The graphs below are
1 Orange line; the references change in ppm compared to its average
2 Blue line; the room temperature change in degrees C compared to its average.

The experiment continues.

regards Rob

Edit ; You can see the set up in the photo in  Reply 250 above, the Refs 4-9 are on the RHS, Ref 1, 3 and 3458 are inside the Black Box, Ref 2 is outside.

[TiN]

Ref 7 is a stinker  

[enut11]

Well done VK5RC. A lot of patient work there. Have you picked a favourite yet?
Further explanation of how you generated the the graphs might be beneficial.
enut11

[VK5RC]

Hi enut11,
The data are all manually processed in Excel, the readings down to uV level are taken by hand.
The room temperature was taken from my trusty Keysight U1253B (no the display hasn't faded yet ! HiHi)
Voltage averages for each reference were calculated and then the individual readings from the 3458 subtracted then multiplied by 10e6 to get ppm variation. The orange graph is this in ppm.
The temperature (blue) curves were done the same way- an average room temp was calculated and the variation from that is shown in C for each reading set. I did it that way so I could use the same axis readings and not be too far out.

I need to get some more data points so I can get enough to do some correlation coefficients of volts vs date (drift) and Volts vs temp.

Ref 7 and 8 are looking pretty good -but I was suprised as HP only rates the 3458 around 8ppm/yr - this is looking a lot better than that - perhaps HP again underquoting.
Regards Rob

[AG7CK]

I have noticed that the US Cal Club thrives. But from recent posts or lack thereof, it seems that the Aussie club is less active. Anyone keeping anything going?

If not, I would like to see a low key, laid back and minimum stress Asia/Pacific(/World) thing. The guy(s) with the best meter(s) closest to cal come forward and offer to help. In exchange they get paid for helping others with "transferring" 10v / 7.xv and checking short time stability / drift (1h/24h) and stdev noise. Add resistance for those interested. No big packages.

IMO it should not be free. Look at the US thing. Months of waiting. Payment weeds out the "nice to be in - it's free" crowd.

Just my 2 satang.

PS I sold my 2x LTZ1000 boards a few years ago. Now I am in the market for a loaner before I finalize my refamp builds and buy a new LTZ1000 chip or board.

I pay shipping both ways, a decent rent and insurance ("real cost or more" deposit) for a ref board "close to real" 10v that I can borrow 2-4 weeks.

[BradC]

I have noticed that the US Cal Club thrives. But from recent posts or lack thereof, it seems that the Aussie club is less active. Anyone keeping anything going?

Not at the moment. We got 2 go-arounds, but we had a couple of fairly long stalls where the references sat and gathered dust. I was the last recipient this time around, but I encountered some issues with my measurements that made me reticent to post results.

In all honesty it's quite $$ to shunt references back and forward across Aus, and I dunno about the other guys but I found limited value in it for me given I had little confidence in my own measurement setup and my reference was by far the worst of the bunch. Personally, I think we'd have to come up with some more defined goals and outcomes before attempting it again.

On the other hand, if & when I want to get some references independently measured, I have people I trust now that I can send them to who have setups that are more accurate than mine.

[AG7CK]

BradC

Thank you for reporting.

I have heard about the results of sending a bunch of refs of varying goodness around without intermediate checking.

What I would like to do is similar to the US club reference going around in a star pattern (or at least frequently being checked by someone with calibrated gear). Also the LT1021 mini reference seems to be a success (on a more modest level) always returning to the owner for checking.

I just wanted to check if there was any interest. I'll guess I just wait and see. If nothing turns up, I will try to buy a "calibrated" LTZ1000 board in the Buy/Sell section. I don't have the time or inclination to build, burn in and then beg someone for "calibration" now.

If a few people are interested we could put in some USD50-100 each for a group buy of an aged board for a few hundred or so here on the forum. Having it reside with the person with the most recent calibration and paying him for the "docking" service should make it possible for everyone to check their gear to at least 5ppm or so. We'll see ...

[enut11]

I have noticed that the US Cal Club thrives. But from recent posts or lack thereof, it seems that the Aussie club is less active. Anyone keeping anything going?

If not, I would like to see a low key, laid back and minimum stress Asia/Pacific(/World) thing. The guy(s) with the best meter(s) closest to cal come forward and offer to help. In exchange they get paid for helping others with "transferring" 10v / 7.xv and checking short time stability / drift (1h/24h) and stdev noise. Add resistance for those interested. No big packages.

IMO it should not be free. Look at the US thing. Months of waiting. Payment weeds out the "nice to be in - it's free" crowd.

Just my 2 satang.

PS I sold my 2x LTZ1000 boards a few years ago. Now I am in the market for a loaner before I finalize my refamp builds and buy a new LTZ1000 chip or board.

I pay shipping both ways, a decent rent and insurance ("real cost or more" deposit) for a ref board "close to real" 10v that I can borrow 2-4 weeks.

Hi @AG7CK
Yes, the Aussie Cal Club is currently in a state of hibernation, except for perhaps @VK5RC with his LTZ experiments.
The initial 2 rounds were about establishing a degree of confidence in uncalibrated quality digital bench meters. And from my perspective it worked well.
Also, I agree with @BradC, it is expensive to ship items around Australia so the next round will have to fulfill a higher need and be confined to more stable and accurate refs.
I dare say that the members may be experimenting in secret for the time being. I know one is well into double-oven temperature stabilisation and this should improve Ref stability by an order of magnitude.
I am near the end of an 18 months programme on 'running in' a number of LM399 refs and will publish results soon. A couple of the 6 chips look promising.
enut11

[VK5RC]

Hi enut11 et al
I have added a new experiment, I have found some nice sockets for some LTZs (DigiKey PN 1-1437508-6-ND) and built a couple of Kx boards (Thanks TiN for design and open sourcing it and SvanGool for OshPark-ing it ) with TE 3-5ppm resistors and 1006 OpAmps,  1k/13.3K and 120R.
I will burn in the LTZ for a couple of months then do some short term temp co studies to see if I can find another 'good' LTZ1000A (or two), I have a total of  6 LTZs to sort out for the new Kx board which will go into a HP 3245 as per TiNs mod on one channel of the HP 3245A.
From the latest measurements of the ongoing experiment, No 7 and 8 are still behaving themselves - despite the weather having changed here quite significantly (cool wet winter 7-13c  from hot dry summer 18-34C).
The Fluke 731B also looks pretty good.
One really interesting factor is the old 3458 itself is doing well - the overall drift of all of the references measurements  looks quite small now - suggesting the 3458 itself is behaving itself. 
 Rob

[enut11]

I have posted my latest results for six LM399 chips that have been powered on now for about 18mths.
https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg1696106/#msg1696106

The idea is for the best one to be part of a precision temperature oven experiment. The oven and controller were designed by a friend but you could also use a diecast metal box.
enut11