NEW PDVS2mini DC Voltage Reference from Ian Johnston - Reviewed.

[GingGangGooly]

Any idea of cost for a new 1.6 device?
(for budget purposes) 👍

[Ecogeek]

Hi Johannes, thanks for the update and all the best. I have a question?  For the new version of PDVS2mini, has the LM399 been upgraded to the ADR1399? Or is this an option when ordering?   
It would seem the ADR1399 has several advantages over the older model including lower noise, be it at the cost of a higher zener current and lower battery run time.
regards from Australia

[wrytech]

To address the points brought up:

• Hope the first batch can go on sale in around 2 weeks; all things are bureaucratic things are set up now and the things at hand are more logistical now. Started calibrating the first half of the first batch today, the second half is still burning in until end of next week, gathering packaging, etc. ... People registered on the newsletter on the website will be the first ones to be notified, with further announcements here, etc. then some time later
• Budget-wise I would allocate 359€ net plus shipping (which I will try to keep at what I pay plus packaging, etc.)
• At this point no upgrades / changes to the analogue part of the design have been done. First step is to get v1.6 where Ians units were as well. Also have partial stock left for around 150 units which I will use up before making relevant changes to the design. Would also like to be able to quantify the advantages in some way when changing over to the ADR1399 for example as it will come with an increase in price as well which further complicates things. So, this is something more for the mid to long term...

Firmware is fully updated as well and now also supports the internal temperature and new calibration point via serial. A big thanks to Ian for kindly updating WinGPIB to be compatible with the v1.6 units as well so quickly!

Thanks
Johannes

[wrytech]

And the shop is live: https://www.wrytech.eu/

Units went on sale on Friday, as was announced via the newsletter, but there is some stock left so no worries there (and I am already planning the order for the next batch haha)

All orders were shipped today, so waiting for any feedback to come in now. Thanks to everybody who has already ordered one, signed up for the newsletter or reached out to me in general! I am glad to see the interest and the trust shown - it means a lot to me.

Best,
Johannes

[flo.b]

I could never get my hands on Ians original, but this must be a totally awesome continuation. I'm glad this project is in good hands again

I was wondering a bit about the newly added temperature sensor, but after looking at the Certificate of Calibration which comes with the unit, the Internal Temperature during Calibration is stated there as well in addition to the ambient temperature, so it all makes sense.

Another issue is that I cannot find any mentions about using non-rechargable 9V batteries. I found some article saying it's not recommended but there was no source or reason given (probably safety).
I don't have rechargable ones lying around, so I'm using Varta 9V Lithium with 1200mAh. Will last only about 24 hours though, so not ideal, especially considering the price of those.
Obviously I won't connect external power, and I've disabled charging in the options as well.

Then I had the idea to burn this in for a long long time (potentially years) which brings up a concern: Is there a MTBF or something specified for the display? Could it possibly be switched off per software? Or is this a non-issue?

[ivo]

Another issue is that I cannot find any mentions about using non-rechargable 9V batteries. I found some article saying it's not recommended but there was no source or reason given (probably safety).
I don't have rechargable ones lying around, so I'm using Varta 9V Lithium with 1200mAh. Will last only about 24 hours though, so not ideal, especially considering the price of those.
Obviously I won't connect external power, and I've disabled charging in the options as well.

A lot of the time this is simply because, being human, we'll forget that we left a 9V alkaline cell in our precious device, leave it for 6 months, then by murphy's law come back and see that it has been ruined by leaking in that time. It's also possible that 9V alkalines might not stand up very well to the inrush current of the heating reference when the device turns on, given it's effectively 12 tiny battery cells in series. Or just at the rate they'll get drained, you'll be making a lot of environmental waste...

[Kleinstein]

The display is a simple passive LCD. There should be not issue with keeping it running for a long time. So no need to turn it off.

[krebacz]

I have received mine middle last week and so far I am very happy with it.
I am a beggining voltnut - so a Keithley DMM6500 for now (6.5 digits).
The PDVS 2 Mini 1.6 has firmware 1.11 and, after a brief warm up (28+ deg C internal, about 5 mins from ambient 23-24 now) is within +- 1 LSD - 10uV on 10V range. On 1V and 100mV ranges it is similar, sometimes up to 20uV.
My Keithley has the last (and first - factory) cal date of 05.2023.

Everything seems in order and the accuracy can flow to my handheld meters.

Thanks Johannes for the quick delivery and an amazing continuation to Ian's work!

[wrytech]

Thanks a lot for the feedback provided and the units shown here - great to see them put to use!

Non rechargeable batteries can be used, of course, as long as nothing is connected to the input jack to prevent any chance of the PDVS 2 Mini trying to charge them. Reasons against using non rechargeable ones are mostly related to convienience and cost, as it gets quite tedious and ultimately expensive to constantly exchange the batteries..
Inrush current should not really be a problem, as there is a small resistor in series with the heater limiting it during startup.

Regarding the LCD, I dont really have any concerns regarding longevity, as so far I am not aware of any problems being reported for Ian's units that are out there. It's socketed anyway, so it can be fairly easily exchanged if required. However, I do not recommend removing it for any other reason, as it's somewhat fiddly to get it to sit right with all the pins and quite hard to pull out without breaking the display, as I found out quite quickly 

Thanks,
Johannes

[IanJ]

The display is not an OLED and so does not degrade over time in the same way. The LCDs are robust, feel free to leave them powered up for many years. In addition, I never had faulty ones ever from memory.

There is a trick I used to remove the LCDs, use the handle of your side cutters (plastic) under the LCD and wedge it up a corner at a time……..enough at one side till it’s loose enough to pull it off by hand.

Ian

[J-R]

I see this latest batch has sold out.  Any news on future production runs or a more regular/reliable supply?

[wrytech]

I did start production of the next batch over the weekend. Had the PCBs here for a longer time, but had some units left in stock, that then all sold out in a couple of days...

With the burn in required the units should become available towards the end of November. Will announce it here then and via the newsletter.

Best,
Johannes