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)
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
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.
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?
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
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
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.
+1 for interest from Australia (Sydney).
(Subscribed to the thread, but forgot to jump in.)
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 t2kv. Thanks for joining in. I am a novice volts-nut. What is your expertise?
What type of DMM do you want to calibrate?
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
I'm whatever the rank below novice is.
I'm whatever the rank below novice is.
We could split up Novice in Low/Mid/High
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.