DMM Volts/Ohm Calibration Club - anyone interested?

[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