NEW PDVS2mini DC Voltage Reference from Ian Johnston - Reviewed - NOW WRYTECH - Page 1
Forum section: electronics / general

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 27, 2019, 10:07:36 pm
content: Hi All,I thought I would pop this here, I just published a review of a new piece of equipment from Ian Johnston, the PDVS2mini, which is a 0-10V DC voltage reference.No doubt you will spot things I am doing wrong, I'm not a metrology guy after all, but hopefully the video demonstrates the capabilities of the unit.

author: IanJ
author_rank: Unknown
timestamp: August 28, 2019, 03:25:03 pm
content: Hi all,Working on a couple of software bugs at the moment, mostly down to the math.h library which isn't great on these small AVR's (it can't add or subtract properly!). So, having to write (C++) around the issue which is a pain.Scott's low end non-linearity problem I don't experience on my own PDSV2mini's here.......so some detective work is required.Prototyping Happy days!Ian.

author: Svgeesus
author_rank: Regular Contributor
timestamp: August 28, 2019, 04:07:39 pm
content: So, the Integral Non-Linearity is higher than the PSVS2, but because resolution is also higher it is compensated for in software?

author: branadic
author_rank: Super Contributor
timestamp: August 28, 2019, 04:25:30 pm
content: Scott, your meter also has INL which is not zero. You could use your F343 and make differential measurements to get more into that.-branadic-

author: IanJ
author_rank: Unknown
timestamp: August 28, 2019, 06:11:29 pm
content: Quote from: Svgeesus on August 28, 2019, 04:07:39 pmPDVS2 (18-bit DAC9881) INL = +/-2 LSB typical, +/- 3 LSB max.PDVS2mini (20-bit MAX5719A) INL = +/- 1 LSB typical, +/- 20 LSB max.The +/- 20 LSB is scary (when volt-nutting) so there is 11 y=mx+c calib setpoints between 0 and 10Vdc output (1Vdc apart).......to compensate/help minimize any deviation.An alternative solution would have been to add in an ADC (low INL) and monitor the DAC output and compensate accordingly, but that just pushes the BOM/complexity up..........Ian.

author: MiDi
author_rank: Frequent Contributor
timestamp: August 28, 2019, 08:02:51 pm
content: Quote from: IanJ on August 28, 2019, 03:25:03 pmAssuming the PDSV2mini does no range switch, this simply shows the DNL.The DS states a DNL of +-1LSB@25°C -> +-10uV@10V FS (This means that this DAC even may not be monotonic).And it is unlikely that this is only in the low end, the Fluke meter has not enough resolution to show this accurate in 1V/10V range - as Scott already stated.Ian, are you sure that yours have better DNL?

author: IanJ
author_rank: Unknown
timestamp: August 28, 2019, 10:18:56 pm
content: I have 2 others sitting here from the same batch and an older one......and on my 3458A no real linearity problems (exception: see below) including at the low end.However, I had found an issue with the firmware which generated a 1 or 2bit random inaccuracy. It's a well known math.h library problem (it can't subtract/divide properly and shows up as a rounding error!). It's fixed now and makes a nice difference.This weekend I'll check Scott's video properly and look into the low end issue......but I am beginning to think it's just DNL as we are right down at 1bit step changes......which are magnified in Scott's mV mode on his DMM. My testing has been done on the same 3458A mode across the full range and shows no difference between high or low.Maybe I will try adding a range selection like I did on the PDVS2, an extremely low RDSon Fet and a low tempco resistor or two. This DAC doesnt have the same Vref range unfortunately, but there are other ways. Hmmmm!Ian.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: September 07, 2019, 03:16:01 am
content: Ian did a firmware update to 1.01 which I applied to my prototype unit (Ian corrected a problem the math library, as mentioned above), the unit steps by 10uV without missing a beat now, I barely even noticed the original issue anyway but now it is fixed.

author: IanJ
author_rank: Unknown
timestamp: September 07, 2019, 11:57:36 am
content: Quote from: TheDefpom on September 07, 2019, 03:16:01 amYep, V1.01 is definitely a winner, and subject to some on-going testing being completed I should be going into production in the coming couple weeks.Maths error:-On 8-bit Atmel AVR controllers the float type is 32-bits which makes the limit 6 or 7 digits......close to the bone and causes rounding errors when working at 5dp's.So, rather than rely on the maths library doing any rounding I have taken control of it just before converting and sending to the DAC......thus forcing it the way I want it.Anyone interested in purchasing please use the NOTIFY ME link and as soon as I have stock you'll get an email.https://www.ianjohnston.com/index.php/onlineshop/handheld-precision-digital-voltage-source-2-mini-detailIan.

author: niner_007
author_rank: Frequent Contributor
timestamp: September 08, 2019, 02:07:11 am
content: Can't wait to get oneYou should consider an STM32, not only will it use less power than the AVR, but better software and libraries too

author: IanJ
author_rank: Unknown
timestamp: September 08, 2019, 12:47:01 pm
content: Quote from: niner_007 on September 08, 2019, 02:07:11 amSomething for the future maybe........but what puts me off slightly is the lack of EEprom, albeit they do have EEprom emulation in flash via paged memory or something like that........well, thats as much as I know about STM32 anyways.Ian.

author: niner_007
author_rank: Frequent Contributor
timestamp: September 09, 2019, 03:32:45 am
content: Quote from: IanJ on September 08, 2019, 12:47:01 pmSTM32 have both eeprom (STM32L010F4 for example) and non volatile flash, depending on the model, which will allow you to store calibration constants and so on, but why do you need eeprom specifically? the API for reading and writing to the flash is quite fine, maybe I'm missing something

author: TiN
author_rank: Super Contributor
timestamp: September 09, 2019, 04:04:08 am
content: I don't like STM, their marketing here in TW failed hard when I tried to get some support to consider using STM32 on a project.Now let's get back on topic. I got this little cute PDVS2mini in thermal box, runningfor lifefirst quick and dirty tempco test.I'm sure somebody will dig a photo with $70K vs $300 DC source.Design assembly is nice and tidy, with all critical stuff well cared. Graphical LCD is not backlit, just COG panel. It has decent contrast and main output voltage have nice large digits. The menu system is little unusual but not hard to figure out without any RTFM. There is a help string on the bottom strings to show keypad actions.Access to battery requires removal of 4 screws, and also provide a way to see some internal construction.There is no separate battery compartment or protection over electronic parts, due to low-cost targeting reason, which is understandable.PDVS2mini designed to use two 9V batteries in series, with integrated charger. Unit needs to be powered on to allow charging from external DC jack.I'm working on detailed review/testing, but it will take some time, so here are just some initial dirty results using my secondary equipment (K2002 and Arroyo TECpak controlled box).PDVS2mini is powered by batteries, placed in DIY chamber. Raspberry Pi controls Keithley 2002 as a digitizer, and TECpak 585 for precision temperature control. 40W noname TEC used as cooler/heater, with water-cooling loop dissipating heat into room elsewhere. The sensor in the box is Honeywell HEL-705-1 100 Ohm platinum RTD. This thermal box setup may not look like much, but its able to maintain any programmed temperature from -5 °C to +65 °C with better than 0.008 °C stability over hours.Now to the first test results. The first graph is a plot of +10V output from PDVS, with temperature change from +15.00 °C to +55 °C in a slow and controlled manner. There is soaking time at +35°C for 2 hours, and also at peak max temperature, to get an idea of settling and hysteresis behavior. The horizontal axis is time duration, vertical axis is deviation from initial point at +15 °C, which happened to be +9.999994 VDC +/-2ppm.For illustrative purposes, chart have additional plots of -0.1 ppm/K and -0.2 ppm/K thresholds based on temperature change (using box method) and TEC current readout from Arroyo TECpak 585. Ramp up time for temperature is +0.08333 °C per minute. Measured deviation is -4.0 ppm for +15.0°C to +35°C ramp, and another -5.3 ppm for +35°C to +55°C ramp. Following the TC Box method we can estimate temperature stability at max-0.23 ppm/Kwhich is impressive for $300 USD DAC box!Now same data, but in voltage/temperature scale representation.Hysteresis on fixed temperature points is around ~2ppm but that will need additional verification with proper setupUnit may need additional time, longer than 30min to get temperature soaked to reach equilibrium. This particular temperature chamber does not use forced airflow, and from datalog looks like it need ~30 minutes to equalize temperature change.Stay tuned for moreOne part I'm not very happy about is banana-only output connectors. Once initial testing and calibration verification test is done, these will be for sure changed to some proper low-thermal EMF hardware.If somebody wants particular test setup/conditions - feel free to give feedback.

author: TiN
author_rank: Super Contributor
timestamp: September 09, 2019, 10:01:00 am
content: And battery died after 12.5 hours.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: September 09, 2019, 10:57:18 am
content: When you consider that most people would want to keep this device a long time and that the value of the reference to the particular end user increases over time it would be a shame to lose everything to battery leakage. I would extend the battery connector to an external connector as the very first modification and permanently run from external power.

author: 2N3055
author_rank: Super Contributor
timestamp: September 09, 2019, 11:30:01 am
content: Quote from: chickenHeadKnob on September 09, 2019, 10:57:18 amIf you keep it normal side up (screen up) it will leak to the bottom of the box, not electronics. Also, it uses rechargeable Li-ion PP3 9V batteries that are not leak prone...

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: September 09, 2019, 12:04:06 pm
content: Quote from: 2N3055 on September 09, 2019, 11:30:01 amThat is good to know, I would still want to keep it powered continuously with a linear supply to age the lm399 for the first three years. There-after I suppose you could switch to intermittent power-ups.

author: TiN
author_rank: Super Contributor
timestamp: September 09, 2019, 12:27:13 pm
content: This device is not designed to be a permanent DC voltage standard, but a portable programmable DC source/DAC. LM399 is not really worthy of proper DC standard anyway due to noise/stability and tempco.And it can run long time with external charger/PSU connected to the Charge port. PDVS2mini is much cheaper than another 5.5-digit source alternatives, even tho output is limited to only one 0V - 10V range.Better DAC option are some 30kg+ anchors like Fluke 5440 and alike, for which you need to be in right country/right spot/with cash in hand and will to repair/troubleshoot boards and modules when things go sour.Handy option for beginner volt-nuts. And if you think ~$300 USD is too much, well, MAXIM's eval board with used DAC, without LCD, case, charger or LM399 already cost $190. Another popular "volt-nut" DAC with AD5791 with LTZ ref is even more, close to $500 USD.Don't get me wrong, I'm not implying somebody should calibrate 3458A with PDVS2mini,It's more of educational precision DC source kit, that is fun to have around for some simple tests, without expensive demands for accuracy. And for this role it looks like priced adequate, and 24/7/365 operation is not a requirement.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: September 09, 2019, 12:37:04 pm
content: The unit is pretty damn good for the money, yes it has a dc input jack for charging the batteries, it can run from that in itself, however due to introducing noise via that input, and the extra heat generated during charging Ian recommends that it not be used that way to avoid it affecting the output accuracy.

author: IanJ
author_rank: Unknown
timestamp: September 09, 2019, 05:32:38 pm
content: Apart from the possible introduction of noise depending on your DC power source......and by example running at 20Vdc at the power jack sees the output vary by about 10uV (1bit !) eventually due to the extra internal heat being generated.On disconnecting the DC input it takes approx. 30mins for the unit to return to it's normalized output.I've tried to minimize this heat induced drift by mounting the LM399AH externally, it's under the LCD in it's own little 3D printed conductive PLA thermal cover.Running off DC permanently then has it's issues per above, but is entitely safe. The MAX1873 battery management IC recognizes an external supply and once the battery is detected as fully charged it will cease charging completely and the DC supply is used to feed the rest of the circuit. The batteries remain in isolation effectively and are not in any way trickle charged.I haven't had a Lithium-Ion battery leak yet and I have about 40 of them which have been charged, drained and left sitting for months on end in and out of PDVS's.PS. This unit was never directly designed as a "reference"......it was designed as an adjustable precision voltage source, but with some capabaility of a reference.Quote from my website "With a user adjustable range from a true 0V to 10Vdc and an accuracy/stability down in the uV’s it has a multitude of uses as a calibrator, reference & precision voltage source."But TiN is right.........not a great idea to calibrate a 3458A with it........I'll be in production soon with it.Ian.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 10, 2019, 08:50:16 am
content: Are you planning to add a remote control?

author: IanJ
author_rank: Unknown
timestamp: September 10, 2019, 04:26:30 pm
content: Quote from: MegaVolt on September 10, 2019, 08:50:16 amIt has a serial header and you can control it remotely from a PC already much the same as the PDVS2 with an appropriate adaptor......however, I will just be supplying the Ascii protocol used and not a Windows app (well, I might supply an EXE unsupported).Ian.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 10, 2019, 08:57:54 pm
content: Quote from: IanJ on September 10, 2019, 04:26:30 pmThank. I did not notice the serial connector.

author: IanJ
author_rank: Unknown
timestamp: October 19, 2019, 01:29:52 pm
content: Hi all,I have just made the first batch of units available in my online shop. Here:-https://www.ianjohnston.com/index.php/onlineshop/handheld-precision-digital-voltage-source-2-mini-detailAvailable worldwide with shipping via UPS courier.Thanks,Ian.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 30, 2021, 07:37:15 pm
content: i am not sorry for kicking this topic back alive :-)wow amazing product you made there Jan, all looks super professionalI really like to see some closeups of the mecanical implementation of the LM399you say it is under the display ?and inside 3D printed isolation case ?the display looks like it can be taken out, so this detail could be revealed,

author: Grandchuck
author_rank: Super Contributor
timestamp: December 30, 2021, 09:15:36 pm
content: It is an amazing product. Mine does not seem to be drifting at all. The reason I must use the word "seem" is due to an interim calibration/adjustment for my 3458A. I wasn't careful enough and should have made more measurements and records. I confess to being a bit of a sloppy volt nut

author: IanJ
author_rank: Unknown
timestamp: January 01, 2022, 06:47:02 pm
content: Quote from: oz2cpu on December 30, 2021, 07:37:15 pmHi,Here's the LM399 cover.........3D printed in conductive PLA, and grounded to the pcb GND via it's mounting screw, a pad and a ring around the LM399.

author: IanJ
author_rank: Unknown
timestamp: January 01, 2022, 07:32:23 pm
content: Spec of the conductive PLA from the datasheet:-How Conductive Is It?● Volume resistivity of molded resin (not 3D Printed): 15 ohm-cm● Volume resistivity of 3D printed parts along layers (x/y): 30 ohm-cm● Volume resistivity of 3D printed parts against layers (z): 115 ohm-cm● Resistance of a 10cm length of 1.75mm filament: 2-3kohm● Resistance of a 10cm length of 2.85mm filament: 800-1200ohmIan.

author: Anders Petersson
author_rank: Regular Contributor
timestamp: January 02, 2022, 05:18:52 pm
content: Are there any long-term stability measurements? For example calibration over several years.

author: IanJ
author_rank: Unknown
timestamp: January 02, 2022, 05:35:11 pm
content: Quote from: Anders Petersson on January 02, 2022, 05:18:52 pmThe closest I have is a customer who bought one in Oct. 2019, and then damaged it in Oct. 21 and it was sent to me for repair. A protection diode was replaced and then a full re-cal.Unfortunately, back in 2019 I didn't produce as full a cal cert as I do now, however, you can see the BIT COUNT changes I had made on the re-cal which will give you some idea.As follows:-

author: Anders Petersson
author_rank: Regular Contributor
timestamp: January 03, 2022, 12:15:41 pm
content: Quote from: IanJ on January 02, 2022, 05:35:11 pmThanks. Comparing a few of the data points, I only see 1-2 counts correction.If you place a few units in different storage conditions and record their calibration every few months, that could answer the "tba" placeholder for drift in your specifications to increase the (already high) value of your product.Nitpicking: The certificate specifies 11 digits for voltage output which seems optimistic. Also, including some calibration/accuracy estimation of your 3458A would be helpful.

author: guenthert
author_rank: Frequent Contributor
timestamp: January 09, 2022, 01:05:04 am
content: Quote from: Anders Petersson on January 03, 2022, 12:15:41 pmFirst of all, those numbers are most impressive.There's nothing wrong per se with 11 or more digits, but w/o estimate of the measurement error, they are a bit questionable. Sure, we can look up the uncertainty Agilent promises to better with the 3458A, but that tells us little about your unit nor how much additional error is introduced when measuring the calibrator (I'm sure there are codified / documented best practices, but an ad-hoc approach might be to use an example unit, measure it's voltage a number of times over multiple days, inverting polarity and calculating the standard deviation from that -- that at least gives a hint about the quality / reproduce-ability of the measurement procedure).

author: IanJ
author_rank: Unknown
timestamp: January 09, 2022, 06:20:43 am
content: Thanks guys, some good points there.My automated procedure just logs directly what the 3458A output gave at the time with an NPLC of 100.Are those numbers reproducable?......no, certainly not at 11 digits, but i figured if thats the numbers the 3458A sees then thats what i record. To be honest, i didnt think twice about it.I'll look into pulling those digits back on the cal certs on future ones, or maybe adding a statement to the certs.Thanks,Ian.

author: TiN
author_rank: Super Contributor
timestamp: January 09, 2022, 06:33:10 am
content: Or just remove everything after 7th digit and call it a day.I wonder if Ian considering to use new 1399 reference in PDVS "3" mini version?

author: IanJ
author_rank: Unknown
timestamp: January 09, 2022, 06:51:44 am
content: Quote from: TiN on January 09, 2022, 06:33:10 amHmmmmmm!Ian.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: January 09, 2022, 07:44:59 am
content: Quote from: IanJ on January 09, 2022, 06:20:43 amI would be inclined to leave all the digits there, might even help identify minor drifts with the 3458A... there are "only" 5 decimal places on the PDVS2mini, with the last one known to have a little rounding due to DAC conversion, I really wouldn't worry about it, people will only be looking up to the 5th/6th decimal place I expect, the rest is for your own records.

author: IanJ
author_rank: Unknown
timestamp: January 09, 2022, 09:48:30 am
content: Quote from: TheDefpom on January 09, 2022, 07:44:59 amNIST would have trouble with 11 digits......heading into superconducting JAWS territory.9dp's on my certs are not stable, not reproduceable so kinda pointless being there.If i run the autocal again the numbers wouldnt be the same.The PDVS2mini isnt that stable......so TiN is right, 7 digits will do.It's a Precision Voltage Source, not some high grade piece if metrology gear.Gotta be totally honest/clear when selling.........Ian.Update, it's fixed (example):-Code:volts10.Text = Format(Val(txtr1aBIG.Text), "#00.0000000")

author: J-R
author_rank: Super Contributor
timestamp: April 13, 2022, 10:27:59 pm
content: Has anyone experimented using the PDVS2mini and a resistor voltage divider to generate much smaller voltages or with an external circuit to make a precision current source?

author: skander36
author_rank: Frequent Contributor
timestamp: July 08, 2022, 03:56:52 pm
content: Hi @IanJ !Two quick questions.1. Why aren't you used AD 5791 for DAC?2. The schematics can be obtained, in order to make an output amplifier that can be driven by PDVS2mini?Thank you!

author: IanJ
author_rank: Unknown
timestamp: July 08, 2022, 04:57:43 pm
content: Quote from: skander36 on July 08, 2022, 03:56:52 pmThe AD5791 is very expensive, and requires a more complicated power supply circuit. Easy to do but affects the BOM.The schematic diagram is not available I am afraid.Ian.

author: skander36
author_rank: Frequent Contributor
timestamp: July 08, 2022, 06:12:25 pm
content: Indeed, is more expensive and now is "unobtanium".There is a project with AD5791 as a calibrator but max 20 uV step.I'll see how I will extract output of the calibrator for interfacing an external amplifier.Thank you!

author: deepfryed
author_rank: Unknown
timestamp: October 14, 2023, 01:11:38 am
content: Quote from: IanJ on July 08, 2022, 04:57:43 pmOn that topic, another question is why not use a discrete PWM DAC ? It looks like some of the old HP voltage sources use that design to get 6.5 digit accuracy. I'm only a hobby tinkerer, so if that's a silly question feel free to say so.I'm thinking of making a hobby grade programmable source as learning exercise with a decent 10v reference like LT1021C, with a discrete PWM DAC driven by a STM32, analog switch like ADG1611 and a low pass filter.

author: deepfryed
author_rank: Unknown
timestamp: October 14, 2023, 04:22:43 am
content: Heh, DAC schematic from 3245A. This might explain itStill going to tinker with a simpler version and see how I go

author: skander36
author_rank: Frequent Contributor
timestamp: October 14, 2023, 09:04:10 am
content: About a month Ian has posted on Youtube a repair video of 3246A -https://www.youtube.com/watch?app=desktop&v=0EPc8ttbU3Q

author: p.larner
author_rank: Frequent Contributor
timestamp: December 31, 2023, 05:07:45 pm
content: is the schematic+fw available for this to homebrew one?

author: skander36
author_rank: Frequent Contributor
timestamp: December 31, 2023, 09:46:35 pm
content: Quote from: p.larner on December 31, 2023, 05:07:45 pmhttps://www.eevblog.com/forum/metrology/new-pdvs2mini-dc-voltage-reference-from-ian-johnston-reviewed/msg4287775/#msg4287775

author: J-R
author_rank: Super Contributor
timestamp: February 02, 2024, 07:49:20 am
content: Just saw this on Ian's PDVS2mini page (https://www.ianjohnston.com/index.php/onlineshop/handheld-precision-digital-voltage-source-2-mini-detail):"I have decided for logistical and health reasons to stop making PDVS2mini’s permanently.If you’d like to purchase the rights to the design, all design files and my remaining stock of parts then please contact me.The PDVS2mini is a very successful and well respected product, it deserves to live on.Business enquiries only"

author: deepfryed
author_rank: Unknown
timestamp: February 02, 2024, 08:02:57 am
content: Oh noes, I've always wanted to get one and missed out on the last round. Too bad, hope you're ok Ian. Take care.

author: IanJ
author_rank: Unknown
timestamp: February 02, 2024, 09:49:38 am
content: Yeah I am fine.....health wise nothing drastic just can't hover over the workbench for days-on-end anymore.I've had a few enquiries thus far and options to look at.......hopefully one of them will work out and the PDVS2mini will continue.Ian.

author: J-R
author_rank: Super Contributor
timestamp: February 03, 2024, 03:17:40 am
content: Whew, glad to hear your health issue is nothing drastic!Maybe you could find someone to do the harder parts like populating the PCB. I also think it would still sell at a higher price point, so you could take your time and make fewer?

author: Paul_txl
author_rank: Newbie
timestamp: February 08, 2024, 09:46:40 am
content: I've been looking at buying one for a couple of years but I thought you had stopped selling them post covid. I should have used the "email when available" link, my bad. Glad its nothing too serious thats stopped you and hope you enjoy your other interests.

author: glitchcatcher
author_rank: Contributor
timestamp: February 14, 2024, 12:03:02 am
content: Woah, all the best Mr. Johnston!Absolute bummer though, this product is amazing and deserves to be continued! And I was waiting for the new production..Wish I could help with this, but I'm afraid I lack the experience. Hopefully a new partner can be found soon!

author: J-R
author_rank: Super Contributor
timestamp: March 21, 2024, 03:02:04 am
content: Just saw this:"The design rights to the PDVS2mini has been SOLD.Forwarding information for the new manufacturer will be published soon."

author: IanJ
author_rank: Unknown
timestamp: March 23, 2024, 01:43:05 pm
content: Quote from: J-R on March 21, 2024, 03:02:04 amNearly 5 years of home production of the PDVS2mini and 40yrs in the oil industry (mostly electronics related) it's time to retire, part health issues and part "it's time".The demand for the PDVS2mini has never been higher and I think it will be in great hands, so please give them some time to get their ducks in a row, keep your eye on my website for updates.For me, I am still doing a couple days a week in oil just for a wee while so the folks taking over my work can make good.......so lets, for the moment, call it semi-retirement.Meanwhile I am forging ahead having fun with my YouTube channel and test instrument repairs.......so if you have any faulty gear you don't need then please contact me.Ian.

author: donlisms
author_rank: Frequent Contributor
timestamp: March 23, 2024, 06:26:51 pm
content: Ian, this enhanced picture of what's going on with you is encouraging for those of us who tend to assume the worst. Thanks for the update. All the best!

author: p.larner
author_rank: Frequent Contributor
timestamp: March 31, 2024, 06:40:55 am
content: why not release this as an open source project?.

author: 2N3055
author_rank: Super Contributor
timestamp: March 31, 2024, 08:33:49 am
content: Quote from: p.larner on March 31, 2024, 06:40:55 amAnd why would he?It is a low cost calibrator. Apart from Ian making a nice and elegant design, for users of device 99% of utility of buying it was fact that Ian kept calibrated KS3458 that he calibrated devices with. And he did a top notch job, too.You were buying calibration, mostly, not device per se.Without proper calibration it's not very useful...Without proper calibration it is just a source of stable voltage.And also, people that do the hard work should get paid for it.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: March 31, 2024, 08:45:31 am
content: Ian deserved to earn some money by selling his design to someone that was willing to continue the work and ensure that people could still buy the units, and as mentioned, building the thing is only half of it, a decent calibration of the PDVS2mini is the critical bit there.

author: Kean
author_rank: Unknown
timestamp: March 31, 2024, 10:56:14 am
content: Quote from: p.larner on March 31, 2024, 06:40:55 amIf he was shutting his business down completely, then that would be ideal. It benefits the community and allows existing owners to maintain their units.But as 2N3055 explains, a large part of the value of such a device is in the calibration which your average DIY builder would not have access to.For as long as it is a viable product, it makes much more sense to sell the business/IP as a going concern and have someone continue the manufacture and calibration. While the market is somewhat limited, there was clearly demand as Ian would quickly sell out of each production batch. It took me a few in-stock notifications before I had an opportunity to grab one for myself. His pricing was very fair, and I don't think anyone reputable could provide them significantly cheaper.

author: skander36
author_rank: Frequent Contributor
timestamp: March 31, 2024, 11:25:44 am
content: Quote from: p.larner on March 31, 2024, 06:40:55 amThere are other projects as open sources.One of them is here -https://www.elektormagazine.de/labs/voltage-current-calibrator-0-to-10v-and-0-to-40ma-0001with atempts to replicate here : -https://www.eevblog.com/forum/testgear/elektor-voltage-current-calibrator-project/But as you can see and guys here explain before me, the main issue is the calibration of such device, even the methodology for aquiring repetable results is not easy.

author: J-R
author_rank: Super Contributor
timestamp: May 11, 2024, 08:43:25 pm
content: Ian starts talking a bit about his now sold PDVS2mini design in this podcast starting here:https://youtu.be/kTpmiK5p_Wc?t=1152New owners are making some improvements:https://youtu.be/kTpmiK5p_Wc?t=1923

author: Svgeesus
author_rank: Regular Contributor
timestamp: May 13, 2024, 10:15:19 am
content: For the (now discontinued) PDVS2, the manual says that there is a simple ascii protocol available on request. I have one of these, and would like to be able to program a fairly complex sequence of voltage steps far beyond the 5 steps provided by the windows electable. Is that still available or would I need to contact the new owners of the PDVS2mini?I'm very happy with this as a manually-programmable voltage source, but (in contrast to the observation in the podcast that "everyone was just using it for it's basic functionality" I also want to use it in an automated test setup to examine the performance of voltage-controlled oscillators; this requires around 100 steps for a full test.

author: IanJ
author_rank: Unknown
timestamp: May 13, 2024, 10:23:32 am
content: Go to my website, online shop and look up the manual for the PDVS2mini, the comms protocol is published there……which is almost identical to the PDVS2.I will provide the actual protocol for the PDVS2 on this thread later today.

author: Svgeesus
author_rank: Regular Contributor
timestamp: May 13, 2024, 10:46:41 am
content: Perfect, so <KeyVoltage,0,1.23456> is all it takes in terms of commands(!) wonderful

author: IanJ
author_rank: Unknown
timestamp: May 13, 2024, 05:38:29 pm
content: Quote from: Svgeesus on May 13, 2024, 10:46:41 amThere are slight changes depending on firmware version, but here's the protocol text doc for the PDVS2.Code:PDVS2 Serial Protocol (PVDS2 firmware 3.00)===========================================INTERFACE = USB (FTDI USB Drivers - http://www.ftdichip/Drivers/VCP.htm)BAUD: 250k,N,8,1A simple bi-directional ascii based serial data protocolRate = Data from PDVS2 to PC is sent every 110mSFormat to PC:- VR0,0,12345Format from PC:- <KeyVoltage, 12, 1.23456>The following details all the data being sent from the PDVS2, and only a partial listing of the data from the PC.PDVS2 OUTPUTS TO PC:========================KV,0,Output Voltage of PDVS2BV,0,Battery Voltage or DC Input VoltageBVFM,0,Battery Voltage Feed MultOVF,0,Output Voltage FeedbackOVFM,0,Output Voltage FeedbackdacZ,0,DAC Zero CaldacS,0,DAC Span CalBC,0,Message = DC Input - Charging, DC Input, DC Input - Full, Running on Batteries, Battery Charge high mA!BLI,0,Message = Status - Low, Status - OkMode,0,Message = Main Menu, Normal, Calibration, Settings, Playback, RampVA0,0,Volts Auto SetVA1,0,Volts Auto SetVA2,0,Volts Auto SetVA3,0,Volts Auto SetVA4,0,Volts Auto SetTA0,0,Time Auto SetTA1,0,Time Auto SetTA2,0,Time Auto SetTA3,0,Time Auto SetTA4,0,Time Auto SetAC,0,AutocountAMR,0,Message = Running, StoppedVR0,0,Volts Ramp SetVR1,0,Volts Ramp SetVR2,0,Volts Ramp SetVR3,0,Volts Ramp SetVR4,0,Volts Ramp SetTR0,0,Time Ramp SetTR1,0,Time Ramp SetTR2,0,Time Ramp SetTR3,0,Time Ramp SetTR4,0,Time Ramp SetRC,0,Ramp countRMR,0,Message = Running, StoppedBMIM,0,Battery Monitor IC MultBI,0,Battery currentAL,0,AutoloopRL,0,RamploopSC2,0,Seconds2dacZ2,0,DAC Zero Cal Dac2dacS2,0,DAC Span Cal Dac2VRS,0,Vref SwitchCMS,0,Cal Mode SubOUTPUT FROM PC TO PDVS2:========================<KeyVoltage,0,1.23456>Voltage requested to output from PDVS2<VrefSet,0>Vref setting, 0=10v mode, 1=2v modeIan Johnston

author: ComradeXavier
author_rank: Contributor
timestamp: May 19, 2024, 02:38:37 pm
content: I fumbled my PDVS2mini taking it off the shelf and dropped it onto my bench. Thankfully, it seems to have survived undamaged. I decided its front panel needed some protection from me (and also from the dust that settles on anything I don't touch twice a day).This case has a nice close fit, a satisfying magnetic closure, and a storage slot so I don't lose the charging cable. (I should find where I stashed the cal sheet and stick that in there, too.) I used PETG for impact resistance and strong layer bonding.If anyone has the same butterfingers problem and wants to make their own, I've attached the .step file.Hardware is:M2.5x25 with nylon lock nut, qty 2 (for hinge pins)6x2.7 mm magnet, qty 4 (commonly sold as 6x3 mm, I designed for the actual thickness of the ones I have)

author: wrytech
author_rank: Contributor
timestamp: June 18, 2024, 09:52:18 pm
content: Time for an official update on the PDVS 2 Mini!In the past weeks and months since I have taken over the design from Ian a lot of things happened and thus the PDVS 2 Mini is on a good way to make a return under the newly created wrytech brand.The tasks at hand always alternated between the technical things to ensure that my version will be up to the standards set by Ian and managing all things business related and bureaucratic - with the latter being a lot more involved than expected (who would have thought?).Today I picked my 3458A back up from calibration at ab-precision and it is very comfortably within the 90-day spec for DCV and with that the last open thing from a technical side is taken care of. The first 50 boards of the version 1.6 have been here with me for a couple weeks with everything working smoothly, also thanks to the constant exchange with and inputs from Ian.Changes for the new version 1.6 include:Maximum output voltage increased to 10.22222V from 10.00000V with additional calibration pointAddition of an internal temperature sensorUpdated optics on the front panel and slight changes on the PCBs for improved manufacturability (reverse mount LED for the comms indicator for example), all criticalanalogue circuitry remainscompletlyunchangedOther than that, everything stays the same; all remaining stocked parts, test jigs, etc. have been taken over and as stated already the goal is to continue seamlessly where Ian has left off.For now, one official matter is outstanding, but should be done in the upcoming weeks and the units can go on sale then.To sign up for the newsletter head over towrytech.eu. Updates will be posted here as well and any questions are more than welcome, of course.Thanks again to Ian for the continued support and feedback provided,Johannes

author: IanJ
author_rank: Unknown
timestamp: June 19, 2024, 06:49:41 am
content: All the best Johannes and Wrytech going forward. The PDVS2mini is in good hands.Ian

author: skander36
author_rank: Frequent Contributor
timestamp: June 19, 2024, 07:12:16 am
content: Hi! Alll the best in the start of this takeover of an already success product!My question is if you will take care of the support for the old ver.(calibration, repairs)?Thank you!

author: aronake
author_rank: Frequent Contributor
timestamp: June 19, 2024, 01:36:36 pm
content: 10.2222 Volt is a nice upgrade!How is the temperature sensor implemented?If digital readout by the software, then that opens up for the idea of having say 3 calibration curves, one at 17C, one at 23C and one at 29C then interpolate between these to eliminate much of temperature coefficient of that output. That would be a super cool feature and should not be too difficult to implement if digital temperature sensor is there.

author: aronake
author_rank: Frequent Contributor
timestamp: June 19, 2024, 01:39:31 pm
content: ah, looking at the pictures i see now that there is digital readout on the display. great!

author: tatel
author_rank: Frequent Contributor
timestamp: June 19, 2024, 01:51:11 pm
content: Looking forward to get one of these. Having to send it out of the EU to calibrate, etc, was the bump in the road for me. But if it can be done within the EU, then I want one...Best wishes

author: J-R
author_rank: Super Contributor
timestamp: June 20, 2024, 10:20:28 pm
content: I also would like to know about obtaining calibrations for the previous model. It also would be nice to have a US-based option.

author: wrytech
author_rank: Contributor
timestamp: June 23, 2024, 09:51:55 am
content: Thanks for all the feedback and input provided already, very nice to see!To answer the questions and open points brought up:I will of course also provide (re)calibration and adjustment if needed / wanted for the PDVS 2 Mini and its predecessors.I can also do a firmware update in the process to extend the output of earlier versions to 10.22222V with the additional calibration point as well if wanted, leaving the temperature sensor then as only difference to v1.6.Same goes for repairs for the PDVS 2 Mini - as stated, I have taken over the complete stock of parts from Ian, so I can do exact repairs for previous versions even if components are different nowThe temperature sensor used is a TI TMP112A, with the current value shown on the display. Have not gotten around to add the temperature value to the serial communication protocol, but will do so going forward. Another thing might be a small indicator to show when the unit should have warmed up, as there is around a 10 K temperature difference to ambient once fully warmed up, which takes about 30 mins to settle if the unit was turned off before.Thanks and Best,Johannes

author: cmu2017
author_rank: Contributor
timestamp: July 10, 2024, 12:25:02 pm
content: Hi Johannes,And when can we expect the first ones for sale?

author: GingGangGooly
author_rank: Contributor
timestamp: July 11, 2024, 08:26:28 am
content: Any idea of cost for a new 1.6 device?(for budget purposes) 👍

author: Ecogeek
author_rank: Contributor
timestamp: July 13, 2024, 12:04:04 pm
content: 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

author: wrytech
author_rank: Contributor
timestamp: July 13, 2024, 10:22:22 pm
content: 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 laterBudget-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!ThanksJohannes

author: wrytech
author_rank: Contributor
timestamp: July 29, 2024, 08:25:45 pm
content: 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

author: glitchcatcher
author_rank: Contributor
timestamp: August 08, 2024, 10:13:57 pm
content: 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 againI was wondering a bit about the newly added temperature sensor, but after looking at theCertificate of Calibrationwhich comes with the unit, theInternal Temperature during Calibrationis 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?

author: ivo
author_rank: Regular Contributor
timestamp: August 09, 2024, 02:24:26 am
content: Quote from: flo.b on August 08, 2024, 10:13:57 pmA 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...

author: Kleinstein
author_rank: Super Contributor
timestamp: August 09, 2024, 03:42:19 am
content: 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.

author: krebacz
author_rank: Newbie
timestamp: August 10, 2024, 07:44:54 pm
content: 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!

author: wrytech
author_rank: Contributor
timestamp: August 11, 2024, 10:03:24 pm
content: 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 quicklyThanks,Johannes

author: IanJ
author_rank: Unknown
timestamp: August 12, 2024, 03:04:46 am
content: 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

author: J-R
author_rank: Super Contributor
timestamp: November 03, 2024, 07:12:54 am
content: I see this latest batch has sold out. Any news on future production runs or a more regular/reliable supply?

author: wrytech
author_rank: Contributor
timestamp: November 04, 2024, 01:58:04 pm
content: 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

author: Cyclotron
author_rank: Unknown
timestamp: December 02, 2024, 08:29:15 pm
content: Quote from: wrytech on November 04, 2024, 01:58:04 pmDid I miss the announcement? Per the update above, I thought units would be available for purchase at the end of November.Thanks

author: J-R
author_rank: Super Contributor
timestamp: December 04, 2024, 01:10:25 am
content: I don't think you missed any announcements. He's probably still working on the latest batch.

author: Cyclotron
author_rank: Unknown
timestamp: December 04, 2024, 05:01:27 pm
content: Quote from: J-R on December 04, 2024, 01:10:25 amThanks, I travel a lot and often don't have a chance to check back on the personal stuff I'm working on.I wanted to get one of these when the next batch was out. I think I'm signed up for the emails.

author: J-R
author_rank: Super Contributor
timestamp: December 05, 2024, 12:00:07 am
content: My opinion is that there is not quite as much pent-up demand for these now. The last two took weeks to finally sell. Hopefully he can keep them in stock going forward because it's very annoying to recommend a product that nobody can actually buy! I'm sure making them in batches is more cost-effective, though.

author: IanJ
author_rank: Unknown
timestamp: December 05, 2024, 12:12:42 am
content: Quote from: J-R on December 05, 2024, 12:00:07 amI don’t think so, no change from my days…….probably more demand now.Ian

author: ITArchitect
author_rank: Contributor
timestamp: December 05, 2024, 01:45:15 pm
content: I waited more than a year to get mine and it was worth the wait. Any bench can benefit! I use it every day and would love a backup! Please make more!

author: J-R
author_rank: Super Contributor
timestamp: December 05, 2024, 06:26:31 pm
content: Is this a teaser?https://www.wrytech.eu/cdn/shop/files/DSC03595.jpg

author: skander36
author_rank: Frequent Contributor
timestamp: December 05, 2024, 06:33:19 pm
content: Quote from: J-R on December 05, 2024, 06:26:31 pmI want this!

author: Martinn
author_rank: Frequent Contributor
timestamp: December 07, 2024, 06:09:51 pm
content: Quote from: wrytech on November 04, 2024, 01:58:04 pmNow there are two versions, one with LM399 and one with ADR1399.Which one should I buy? The ADR1399 is fairly new and I am not sure if there is sufficient experience regarding long time stability.Thanks! Martin

author: Cyclotron
author_rank: Unknown
timestamp: December 07, 2024, 06:55:39 pm
content: Quote from: Martinn on December 07, 2024, 06:09:51 pmI went ahead and bought the ADR1399 model. If there's issues long term I can get an LM399 version then. I guess I'll just plug it up and turn it on and let it stay that way on the bench to age. I'll start checking its accuracy each year after my meters are calibrated.

author: Kean
author_rank: Unknown
timestamp: December 09, 2024, 12:42:44 am
content: Hey wrytech,On your page for the IUSL - Isolated USB Serial Link for PDVS 2 Mini, it mentions:QuoteI don't seen any software under the resources tab.Is v1.2 just an updated Windows app, or does it involve newer firmware and if so can end users update firmware on their pre-v1.6 hardware?I have a similar isolated USB serial from DuPPa.net. Pin ordering is different, but I can deal with that.Thanks!

author: telectric
author_rank: Contributor
timestamp: December 09, 2024, 10:25:30 pm
content: Missed the latest go around. Is there an ETA for the next batch?Also, for shipments outside the EU (USA) is the VAT subtracted from the price?Looking forward to having one.Thanks, WT

author: wrytech
author_rank: Contributor
timestamp: December 09, 2024, 11:06:32 pm
content: Finally found some time to catch up here as well...New batch went on sale on Saturday, with anADR1399version now available as well. Apart from the changed reference, nicer gold-plated banana jacks are included as a little extra bonus. Since quite a lot of people asked about the ADR, I decided to go ahead and make this variant as well. The changes in circuitry are small anyway.Currently, the ADR ones are out of stock, but there are 2 more coming that started the burn-in process later. I hope to get them calibrated over the coming weekend and will put them online then. Parts for more ADR1399 are already ordered, with the usual lead time mostly due to the burn in...The goal is definitely to have a stable supply going forward; I just didn’t really know how the reaction to the ADR ones would be.LM399 ones are available- as usual everything that is listed as in stock in the shop will be shipped immediately.Quote from: J-R on December 05, 2024, 06:26:31 pmThat was way faster than I would have imagined and yes this is a teaser. Some work still needs to be done on the software and unit characterization, but I’d say most things of interest are visible in the picture...Quote from: Kean on December 09, 2024, 12:42:44 amThe software hasn’t been uploaded yet, as instructions for updating and a changelog still need to be prepared—I hope to get it done over the coming weekend. New PDVS 2 Minis ship with the updated firmware and no individual IUSL have reached their buyers yet, so not that much of a problem yet...The changes mostly focus on improving serial connection functions and making them more flexible. Currently, the baud rate is fixed at 250,000, which can cause issues since it's somewhat uncommon, and people have reported problems with it. Version 1.2 will be fully backwards compatible and run on pre v1.6 PDVS 2 Minis as well - no worries there.The DuPPa adapters are good and work with the 250,000 baud rate, but dealing with the non-matching pinout became annoying, so I went ahead and made the IUSL.Quote from: telectric on December 09, 2024, 10:25:30 pmSee above, LM399 ones are available, 2 ADR ones are coming on a shorter notice and then more some time early next year (hopefully).VAT is excluded for shipments outside the EU, with import taxes and other fees to be handled by the buyer as usual.Thank you for all the comments, questions, and feedback here! With the usual pre-Christmas rush at my day job, there's quite a bit of juggling to do, so please bear with me if things take longer than expected or if communication is a bit slow on my end.Johannes

author: SHF
author_rank: Regular Contributor
timestamp: December 14, 2024, 11:44:41 am
content: I treated myself to the ADR1399 version, very nice device, works excellently!

author: wrytech
author_rank: Contributor
timestamp: December 15, 2024, 02:51:59 pm
content: Firmware v1.2 is now available for download under the Resources tab on the website:https://www.wrytech.eu/pages/resourcesA PDF file with upgrade instructions and a changelog is also provided.Additionally, the manual has been updated to include information on the new features introduced in this firmware version.Best,Johannes

author: tonyalbus
author_rank: Super Contributor
timestamp: December 18, 2024, 11:13:53 am
content: Received mine yesterday, the ADR1399 version... video review coming soon, but i needed to play with it. could not help to share it.Yeah that feels great, my meters are good!! Yes! Yes!!!(yes its not horizontal, but that is just quickly for the picture)

author: tonyalbus
author_rank: Super Contributor
timestamp: December 19, 2024, 08:49:39 am
content: What software are you guys using for your PDVS2mini for remote control ?have not connected mine yet, but i have the isolated adapter,i have been looking for the software from the screenshot from Ian, but i can't find it . (PDVS2mini 20bit V1.0)also for calibrating the device (calibration for now not needed but who knows for later)i did found some from other:https://github.com/DunningtonAudio/PDVS2miniAppOr for the old one from Ian: (but that is for the older 18 bit i guess prob not to use for this one)https://www.ianjohnston.com/index.php/onlineshop/handheld-precision-digital-voltage-source-v2-detailOr are you using something completely different?

author: J-R
author_rank: Super Contributor
timestamp: December 19, 2024, 09:49:56 am
content: I suppose there will need to be an update to the software to support the 10.22222V output and perhaps some other aspects?But you could try Ian's Windows software:https://web.archive.org/web/20240617223338/https://www.ianjohnston.com/images/stories/IanJ/VoltageSourcePrecision/PDVS2mini/PDVS2mini.zip

author: tonyalbus
author_rank: Super Contributor
timestamp: December 19, 2024, 10:22:43 am
content: Quote from: J-R on December 19, 2024, 09:49:56 amThanks! Yes the intrnet archive, i forgot. Great that was what i was looking for.Ian made some great software for GPIB and just watched an old video how he automated the whole bulk calibration for the PDVS, very impressive stuff.

author: Cyclotron
author_rank: Unknown
timestamp: December 24, 2024, 05:41:09 pm
content: I received my unit yesterday. I regularly get things from mainland China faster. I'm not lodging a complaint; it's just an observation.I highly suspect that the holidays and maybe even Canadian post being offline have impacted global shipping. I ordered a KWeld board out of Toronto that should take 2-3 days to Virginia, and it took 2.5 weeks via FedEx.Okay, what a nice device! I immediately did what most people, I figure, will do: I hooked it up to every meter I had to check its accuracy. I'm happy to say my primary two bench meters are perfect or thereabouts.That means the recent calibrations I've made are likely good.I have noticed a behavior I haven't seen reported, and I wanted to mention it here for WRY TECH and others.I charged mine overnight, and this morning, I was nerding around with it (definitely not fondling). I turned it off and set it aside when I realized I wanted to check the firmware version.I clicked the power button, and the display showed the images in the attached photos. My stomach sank a bit. I think I clicked the button for more time, and it came to life normally.In the end, I can reproduce the results easily. If you just tap the power button the display will pop up some lines and slowly clear. I suspect there's some logic in there that prevents bumping the device and changing the power state. But I'm not sure.

author: IanJ
author_rank: Unknown
timestamp: December 24, 2024, 05:55:01 pm
content: Quote from: Cyclotron on December 24, 2024, 05:41:09 pmThis is caused by not holding the power button down long enough when you want to power it up.The soft power circuit is integrated into the software, so when you just quickly jab the power button it does send 3.3Vdc to the display & uController but not long enough for the software to run and interact with the soft power switch hardware in order to hold the power on permanently.The proper way to power up is to hold the power button for a second or so.....then release.There's nothing wrong with your PDVS2mini.Ian.

author: glitchcatcher
author_rank: Contributor
timestamp: December 24, 2024, 05:56:02 pm
content: Quote from: Cyclotron on December 24, 2024, 05:41:09 pmIt's perfectly normal behavior. IIRC it's written in the manual that you have to hold the power button to turn it on.It's either against accidental power on as you say, or the µC is disconnected from the battery by that push button, and holding it down energizes the circuit and it takes some time to initialize and bypass that button electronically so the device stays on. That would be a power saving feature then which is just a guess. Wondering if that's still necessary with todays µCs standby/sleep currents.

author: Cyclotron
author_rank: Unknown
timestamp: December 24, 2024, 08:57:14 pm
content: Quote from: IanJ on December 24, 2024, 05:55:01 pmYup, that's what I figured, and I just didn't communicate well in my post. I only posted about it in case others saw it, and, as I did, a mild panic attack. I prefer it like it is; as you said, there is nothing wrong with it.

author: wrytech
author_rank: Contributor
timestamp: December 28, 2024, 06:22:01 pm
content: Finally following up on the things that came up over the holidays....Quote from: tonyalbus on December 19, 2024, 08:49:39 amI typically use the Arduino IDE’s Serial Monitor for quick testing or custom Python scripts for more complex tasks. The latter also inspired the changes in software version 1.2, making it easier to reliably retrieve data (mainly temperature) using the “request” option.I’ve mentioned before that I feel the serial connection is underutilized, likely due to the lack of examples and showcases. It’s on my list to address, but other tasks have taken priority for now.That said, I encourage you to explore the commands—it’s as simple as opening the Arduino IDE’s Serial Monitor, connecting a PDVS 2 Mini, and sending <KeyVoltage,0,1.23456> to set the voltage to 1.23456 V.Beyond calibration, I also use the serial connection to remotely set the voltage on my Agilent E3616A supply, which only accepts control voltages and lacks a direct digital interface. I have used this to simulate battery discharge over a longer time period for example.Quote from: Cyclotron on December 24, 2024, 05:41:09 pmShipping has been challenging because I handle low volumes, which made setting up logistics difficult initially due to minimum quantity requirements. DHL ended up being the best option here. However, since the packages transition through both national postal services, delays are sometimes unavoidable.Tracking is included with all shipments, and so far, there haven’t been any major issues, with successful deliveries from Alaska to New South Wales. Still, I’ll look into adding an express shipping option that DHL already offers.Recently, I introduced a cheaper rate for shipping links and the IUSL using “Warenpost International.” So far, this has only been announced in the newsletter.Quote from: Cyclotron on December 24, 2024, 05:41:09 pmI’ve noticed streaks on the LCD when turning on devices for the first time after mounting the display in some cases as well. I suspect this is due to stray voltages in the display that take time to dissipate. This issue can also occur if the batteries are removed without switching the unit off. It can take some time for the streaks to disappear, but so far, I haven’t encountered a display with any permanent marks or damage.As Ian has already kindly mentioned, there’s absolutely nothing to worry about.Let me know if there’s anything else you’d like me to clarify or address,Johannes

author: IanJ
author_rank: Unknown
timestamp: December 29, 2024, 12:24:18 pm
content: Quote from: wrytech on December 28, 2024, 06:22:01 pmYes, I noticed that also sometimes......I.E. if I remember correctly, on the very first boot fresh from the reflow oven and after the firmware is loaded, the Flash ram area in the uC doesn't contain it's default parameters yet and so the LCD can be a bit random and doesn't clear at boot. It could probably be coded around that in setup() but it's only ever going to happen once in it's lifetime......unless the user as per here jabs the power button.Ian.

author: Cyclotron
author_rank: Unknown
timestamp: January 03, 2025, 03:34:20 am
content: Quote from: IanJ on December 29, 2024, 12:24:18 pmAnd now I've been called a "user". Oh man, that stings a bit. I've been an engineer and an Architect in Information Technology for nearly 30 years. "USER" has always been a 4 letter word.I guess we are all users at some point.

author: tonyalbus
author_rank: Super Contributor
timestamp: January 26, 2025, 09:12:56 am
content: Here it is on my desk, the change of weather or the wind blowing the other way, coused my last digit not to match in the videobut man, the thing is clean and stable...

author: ITArchitect
author_rank: Contributor
timestamp: March 04, 2025, 01:00:25 am
content: These are sold out, when will the next batch be available?

author: nwind
author_rank: Regular Contributor
timestamp: May 07, 2025, 07:57:23 pm
content: Quote from: ITArchitect on March 04, 2025, 01:00:25 amPlease let us know.

author: Shimonu
author_rank: Regular Contributor
timestamp: May 09, 2025, 06:02:01 pm
content: I would also like to know when they will be available again

author: wrytech
author_rank: Contributor
timestamp: May 12, 2025, 06:43:40 pm
content: Time for an update!Things have been somewhat quiet here and this is because I have been quite busy over the last couple months. The last units just sold out last week, and the next batch will take a little longer, as I've been working on a larger revision in the meantime.The motivation for these v2 units came from me using up the parts I had taken over from Ian, which gives me more flexibility going forward. Initially, only the microcontroller was meant to change, but as time went by, more things were changed across three revisions of v2 prototypes.The changes made include:Removal of the daughter PCB by integrating the charging circuitry on the main PCB. New 5.5x2.5 mm DC jack. This makes final assembly easier and the more standard size and position of the DC jack allows usage of angled plugsNew microcontroller (AVR64DB48) running at a faster clock speed and significant portions of the software rewritten, leading to a snappier feel. Additionally control functionalities like charging voltage detection and measurement have been improved. Power and ok buttons have been combined into one; the unit is now turned off via the main menu, which prevents accidental shutdowns.Some careful changes have been made to the analogue circuitry as well. My initial tests here show improvement for wideband noise (around -20%) and reduced power consumption for the complete unit (also around -20%). The temperature coefficient remains the final parameter to be checked. Overall layout around ADR1399 and MAX5719A is unchanged.I'm excited about the changes, as final assembly will be simplified, the software feels very good (which might be something mostly appreciated by me, since all units get their final calibration manually), and some improvements in performance are to be expected.The timeframe for availability now depends on the results of the tempco measurements. If a significant decrease in performance is observed, a fallback to the original design remains an option of course.If all goes well, I expect availability in around 6 to 8 weeks.Pictures are attached, happy to answer any further comments and questions.Best,Johannes

author: Cyclotron
author_rank: Unknown
timestamp: July 21, 2025, 04:45:21 am
content: Looking forward to seeing your new updates.Any chance you'll build some current standards any time soon?

author: SHF
author_rank: Regular Contributor
timestamp: July 26, 2025, 09:42:15 am
content: Quote from: Cyclotron on July 21, 2025, 04:45:21 amhttps://www.wrytech.eu/products/pdvs-2-mini-v2New Version

author: Furna
author_rank: Frequent Contributor
timestamp: July 26, 2025, 05:30:45 pm
content: Quote from: SHF on July 26, 2025, 09:42:15 amThat web page had been tormenting me since 11:30 this morning when I received the newsletter email.I had to stop it from tormenting me, and there was only one way: click the buy button.

author: bastl_r
author_rank: Regular Contributor
timestamp: July 26, 2025, 06:38:06 pm
content: Was that good for your personal well-being or not?

author: Furna
author_rank: Frequent Contributor
timestamp: July 26, 2025, 08:43:27 pm
content: Quote from: bastl_r on July 26, 2025, 06:38:06 pmWell I feel definitely better.The web page stopped tormenting me but I am now freaking out waiting to receive the unit.Luckily this will happen soon, since DHL shouldn't have troubles to deliver in the same city.Then the bank account will start tormenting me

author: ledtester
author_rank: Super Contributor
timestamp: July 26, 2025, 08:51:30 pm
content: Quote from: FurnaIt'll probably first go to a central global hub to get grouped with all the other packages going to your city.

author: Furna
author_rank: Frequent Contributor
timestamp: July 29, 2025, 05:46:35 pm
content: Quote from: ledtester on July 26, 2025, 08:51:30 pmIndeed DHL tried to deliver today; unfortunately I was not home and the sender (correctly) ordered the package to be delivered in person and not left at my premise.I have time to charge the batteries

author: Furna
author_rank: Frequent Contributor
timestamp: July 30, 2025, 08:03:13 pm
content: I collected earlier today the package from DHL.Software v2.0 IMHO has at least one bug; see photo. At first boot, I entered the Settings menu and exited without saving.When I entered the Settings menu again (with no rebbot) I foud what you see in the photo.Software v2.0 is a little different than previous version.I am not able to access the serial settings menu via press and hold the LEFT and RIGHT buttons simultaneously.Anyway serial is working; it just start at the first command sent via a terminal application (I am using Putty).You can also restore defualt values for the device (so I have back the correct values for the Settings menu).Playing a bit with the device ...

author: wolfy007
author_rank: Frequent Contributor
timestamp: August 05, 2025, 03:29:49 pm
content: wow, already sold out.

author: Furna
author_rank: Frequent Contributor
timestamp: August 05, 2025, 05:08:58 pm
content: Quote from: Furna on July 30, 2025, 08:03:13 pmMeanwhile this bug has been already corrected and was obviously due to the empty EEPROM.<RestoreFactorySettings> serial command now also saves the values in EEPROM and new devices already have firmware v2.01Unfortunately the firmware is not yet available on the web site and I am not sure to upgrade just for this samll change.Indeed the web site has the new manual for firmware v2.01I proposed Johannes to implement a new value "Half" for Charge Enable setting to charge the batteries to "storage" Voltage value ( 3.7*4=14.8 )I am keeping the unit on all the time with a noisy switching PSU (as far as I know non damage should happen to circuit or compononents) but measurement will be done on batteries only.Let's see ... currently I reached the result switching to "No" at half of the charge.Yes the unit is already sold out ... remember "one man (not full time I guess) company".

author: Gertjan
author_rank: Frequent Contributor
timestamp: August 05, 2025, 05:59:26 pm
content: Sorry, I bought apparently the last one. Next day it was marked "sold out".Will receive it tomorrow.Regards, Gertjan.

author: wrytech
author_rank: Contributor
timestamp: August 05, 2025, 09:04:31 pm
content: Hi all,Thanks for the interest, the purchases, and the feedback so far. I’m quite happy with how the v2 introduction has gone.Initial units were limited due to housings in stock running low. New one are currently in production and I have fully assembled and burned in PCBs ready, so restock won't take too long once the housings arrive.Thanks also to Furna for spotting and pointing out the EEPROM bug and the discussion around it. It’s already fixed in units shipped over the weekend. The issue only appeared on new units if settings were exited without saving. Using "Save & Exit" once writes the needed values to EEPROM (as intended), and the problem won’t occur again. Root cause was the unit trying to restore values from an empty EEPROM; on power-up, defaults are loaded, so it slipped through initial testing. Really don't think I would have been able to find this one by myself hahaAs always, looking forward to more discussions, feedback, etc.Johannes

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 10, 2025, 12:09:51 am
content: Johannes, I emailed you the other day to see if you were interested in sending me a unit to review, to replace my existing Ian Johnston V1 prototype (which this entire thread is based on), haven't had a response so wasn't sure if you got it or not, or if you are not interested in sending a V2 to me to review.

author: Gertjan
author_rank: Frequent Contributor
timestamp: August 12, 2025, 02:15:01 pm
content: A heads-up on the EBL 6F22 Li-ion 600 mAh batteriesTL;DR: These batteries are now having a new appearance. But likely are still the same batteries.I bought 4 EBL 6F22 Li-ion 600 mAh batteries on Amazon. As recommended by Wrytech, and indeed in Europe Amazon seems to be the easiest supplier.The photo on Amazon showed the well known batteries:EBL_old_Amazon-1000pix.pngBut what I received looked completely different:IMG_4447__EBL_Li-Ion_battery_new-2000pix.jpgThe batteries as received measured 7,5V. After charging, I measured 8,4V. So it seems they still contain the same 2 Li-Ion batteries in series as before.Two of these new EBL batteries are now in my PDVS 2 mini V2 for a week, and function without any problems.regards, Gertjan.

author: IanJ
author_rank: Unknown
timestamp: August 12, 2025, 03:20:56 pm
content: I believe EBL rebranded their entire product line. They sent out a press release Dec. 2024.Still my 6F22 batteries of choice.Ian

author: J-R
author_rank: Super Contributor
timestamp: August 12, 2025, 05:15:22 pm
content: https://www.eblofficial.com/products/9v-rechargeable-batteries

author: Gertjan
author_rank: Frequent Contributor
timestamp: August 15, 2025, 01:36:26 pm
content: I wrotea driver for the PDVS 2 mini v2 forTestController, a Program that can log from many multimeters.With this driver TestController can set the PDVS2mini Output voltage. For example, with the "Param sweeper" popup one can do sweeps of the output Voltage. The PDVS2mini Set Voltage, Internal Temperature, and Battery Voltage can be read-out and logged. Additional Status info is read out in the Setup Menu.Please note: This configuration file is for the PDVS 2 miniv2. Unfortunately Wrytrech made changes to the communication protocol. So this driver won't work with older (pre v2) PVDS2 mini's. However, it won't be too difficult to adjust this device configuration file to the older commands.Please find more info, and the definition file here:configuration file for the Wrytech PDVS 2 mini v2.(It will be added to the TestController distribution with the next update)Regards, Gertjan.

author: wolfy007
author_rank: Frequent Contributor
timestamp: September 13, 2025, 05:26:46 am
content: still sold out?

author: SHF
author_rank: Regular Contributor
timestamp: September 15, 2025, 11:30:40 am
content: Quote from: wolfy007 on September 13, 2025, 05:26:46 amyeshttps://www.wrytech.eu/products/pdvs-2-mini-v2

author: Gertjan
author_rank: Frequent Contributor
timestamp: September 19, 2025, 10:33:09 am
content: Start-up behaviour of Wrytech PDVS2 mini v2I measured the start-up / warm-up behaviour of my Wrytech PDVS2 mini v2 @ 10V output.The measurement starts at switching on the cold PDVS2 mini v2The red curve is the output of my PDVS2 mini v2, as measured by the 3458A DMM. The 3458A was pre warmed-up for 24 hours, and ACAL was done 15 minutes before starting the measurement.The distance between Y axis grid lines represents 1ppm / 10uV.The blue horizontal line represents where I think 10V really is*The grey line is the measured PDVS2 mini v2 internal temperature.Green & Pink are the room temperature and humidity. I managed to keep the room temperature constant.Full size graph:PDVS2-mini-v2-start-up-3458A-3-hours-1200pix.png- Within 15 minutes the PDVS2 mini v2 is in spec (Specced accuracy: ±50 μV)- But it takes about 1:40 hours before the PDVS2 mini v2 is really stable.- Note that the output voltage curve is more or less reciprocal with the internal temperature curve. This suggests that tempco is the biggest contributor the output variation.- In this measurement the PDVS2 mini v2 output is about 1,5 ppm high. Possibly because of tempco, as the internal temperature is around 27,6degr.C, and the temperature stated in my Wrytech calibration sheet is 30.4degr. C. Something to look into.* This 3458A was calibrated a year ago by Keysight Boeblingen. I calculated the yearly drift using previous calibrations, and corrected for the last year. (Keysight states an uncertainty of 1,5ppm for the 10V range)regards, Gertjan.

author: Gertjan
author_rank: Frequent Contributor
timestamp: September 21, 2025, 02:31:51 pm
content: After the measurement in previous post, I was curious what part of the difference between the 10V of the PDVS2 mini v2 and the 3458A was due to tempco. Internal temperature of the PDVS2 mini during that measurement was 27.6°C, while this temperature was 30.4°C during the Wrytech calibration.So I put the PDVS2 mini in a big cookie tin, together with a power resistor on a heatsink. This way I could add some warmth to the PDVS2 mini environment, and slowly rise its internal temperature.Full size graph:PDVS2-mini-v2-temperature-variation-1200pix.pngAgain the red curve is the output of my PDVS2 mini v2, as measured by the 3458A DMM. And the blue horizontal line represents where I think 10V really is.Dark grey is the PDVS2 mini internal temperature, and pink is the room temperature.The measurement starts where the measurement in previous post stopped. After applying some heat in the cookie tin (about 1.5W), temperatures are slowly rising, and as expected, the PDVS2 mini output drops.Where the red line crosses the blue line, the PDVS2 mini output is exactly 10V (according to me)A bit after that point, at about 1:00, I stopped adding warmth, and opened the cookie tin to let the PDVS2 mini cool down again. This resulted on the second crossing of the blue line at about 1:45.Then I tried to add just enough warmth to get the PDVS2mini v2 at just the optimum temperature, and keep it there. Alas, at 2:45 the batteries where empty, and the PDVS2 mini switched off (battery voltage is shown by the light blue line)When looking at what internal temperatures the PDVS2 mini outputs precisely 10V, it is on average 29.5°C. And that is close to the Wrytech calibration sheet temperature of 30.4°C.So "my idea of 10V" matches very well with the "Wrytech idea of 10V"But, considering all uncertainties involved, this could just be a happy coincidence... (on my end I would expect an overall uncertainty of about 2ppm)Also, it seems my PDVS2 mini v2 is a bit more sensitive to temperature then expected, so that needs more investigation....regards, Gertjan.

author: Gertjan
author_rank: Frequent Contributor
timestamp: September 24, 2025, 05:40:44 pm
content: Wrytech PDVS2 mini v2 linearityI measured the linearity of my Wrytech PDSV2mini v2.The PDVS2 mini is controlled by TestContoller, and sweeps from 1V to 10.2V in 1230 steps Its output is measured with with the Agilent 3458A, on the 10V range in manual ranging.A math function in TestController calculates the difference between input and output.Full size graph:PDVS2-mini-v2-linearity-1-10.2V-100NPLC-1200pix.pngThe red trace is the PDVS2mini v2 output, measured with the 3458A, blue trace is the set value of the PDVS2mini output. (hardly visible, because it is under the 3458A trace)The dark grey trace is difference between measured output and set value, in PPM.Pink trace is the internal temperature of the PDVS2mini, to check if variations in the difference trace are correlated with temperature.I tried to minimise the "noise" in the difference trace.- Changing from 10NLPC to 100NLPC did not make much difference. So it is not a noisy PDVS2mini v2 output.- Using a longer delay before taking the measurement, to let things stabilise, did not make any difference. The PDVS2mini v2 settles quickly, and I used a Teflon measurement cable with low absorption. (This measurement uses 0,5sec delay between a set-step and taking the corresponding measurement, I also tested with 2sec delay)My conclusion is that most of this "noise" is due to the 20bit resolution of the MAX5719 DAC.Mostly it is well in spec (Accuracy = Within 50 µV = 5ppm @ 10V)Only on the low end the differences become somewhat larger.Of course one has to realise that this not only a measurement of the PDVS2mini v2 linearity, but also of the 3458A.Linearity is excellent. A flat line with only a hint of rise below 5V. It clearly pays off that the calibration has 11 set-points, not just "min" and "max". (MAX5719 INL = ±20LSB Max.)I also took measurements with a sweep from 0V to 1V, to better explore the low voltage part. The 3458A was now in it's 1V range, so with optimal resolution and linearity for this measurement:Full size graph:PDVS2-mini-v2-linearity-0-1V-100NPLC-1200pix.pngIndeed the differences become worse with lower voltages. Note that the difference scale is now coarser: ±100ppm instead of ±25ppm previously.Extra shielding (cookie tin, guarding) made no difference. The PDVS2mini was galvanically isolated from the measurement PC using the IUSL Isolated USB Serial Link.I think we see the bottom of the DAC barrel.Linearity is still excellent until about 0.3V, below it becomes a bit worse.Fortunately I can't think of a use case for these very low output voltages. (And a 100ppm deviation is still only 0,01%.Edit:For more insight seethis postbelow.regards, Gertjan.

author: HKJ
author_rank: Super Contributor
timestamp: September 24, 2025, 06:12:19 pm
content: Nice, but I am missing the actual error in uV. If you have saved the data it is easy to add it.Use manual scale in TC and place it away from the center.

author: Gertjan
author_rank: Frequent Contributor
timestamp: September 24, 2025, 06:38:23 pm
content: Quote from: HKJ on September 24, 2025, 06:12:19 pmHi HKJ,Why do you prefer the error in uV instead of PPM?I will add it tomorrow morning, and maybe I will I will find out when I see it.regards, Gertjan.

author: HKJ
author_rank: Super Contributor
timestamp: September 24, 2025, 06:55:55 pm
content: Quote from: Gertjan on September 24, 2025, 06:38:23 pmI like both, the information you get from them are different.

author: Gertjan
author_rank: Frequent Contributor
timestamp: September 25, 2025, 08:02:00 am
content: I added the difference in uV to the PDVS2 mini v2 linearity measurement:Full size graph:PDVS2-mini-v2-linearity-1-10.2V-100NPLC_uV-1200pix.pngNow the difference in ppm is in dark grey, and the difference in uV is in pink.Indeed, this is interesting to see:- The uV graph shows much clearer that there is an offset of ≈7uV @10V, witch declines towards 1V output.(This is the 5.6uV calibration offset of the 3458A, combined with ≈1.5uV tempco of the PDVS2mini v2. For looking at linearity this is not important)- The absolute error (in uV) remains the same over the whole 1-10V range, and that is why the relative error (in ppm) increases towards lower output voltages. (Of course, the offset decreases with the attenuation of the output voltage)- Both graphs work well for looking at linearity. Like showing the small dip around 5V. But with the uV graph, linearity is easier to judge.With these new insights, I also added the uV graph to the 0-1V chart:Full size graph:PDVS2-mini-v2-linearity-0-1V-100NPLC_uV-1200pix.pngNow the low end looks much better!We can see that the absolute error does not increase at low voltages. And linearity remains good.But of course, the relative error is getting larger, as that error becomes an increasing bigger part of the output when the voltage becomes smaller. As the ppm graph is showing.Thank you HKJ, for giving me this nudge.regards, Gertjan.

author: branadic
author_rank: Super Contributor
timestamp: September 25, 2025, 09:17:09 am
content: The drawback of MAX5791 used in the PVDS2mini is its maximum reference voltage of Vdd (max. 5.5 V), which means that the DAC output voltage is followed by a gain 2x boost stage to get you the 10 V and that the reference voltage of the LM399/ADR1399 is scaled down to 5 V'ish to begin with. That design choice was due to the lower BOM cost compared to AD5791. However from a performance perspective, AD5791 beats the MAX5791.-branadic-

author: IanJ
author_rank: Unknown
timestamp: September 25, 2025, 03:58:08 pm
content: Quote from: branadic on September 25, 2025, 09:17:09 amAll day long.......AD5791ARUZ = £57+VATAD5791BRUZ = £88+VATMAX5719AGST = £33+VATThe AD5791 has a much, much better INL, but is more complicated to use as it needs a split rail power supply. Believe me I tried back in the day but I just couldn't get the BOM cost numbers to work.......and sadly there wasn't really any other 20bit DAC's available in that class. I remember even trying a dual DAC prototype......but that gets quite complicated......I still have nightmares about it!The MAX5719 is a great, GREAT compromise all things considered......IMHO.PS. I was always hoping a successor to the MAX5719 would appear, maybe 24bit, better INL or more flexible VREF but it never appeared......and as far as I know still hasn't!Ian.

author: CalibrationGuy
author_rank: Unknown
timestamp: September 27, 2025, 09:34:53 pm
content: The Ectron 1120 did a dual dac architecture. I've built a number of dual 16bit units for fun. Works well but the costs add up quickly so maybe justified in a $1,000.00+ device.TomG.

author: Gertjan
author_rank: Frequent Contributor
timestamp: October 02, 2025, 05:57:53 pm
content: PDVS2mini v2 Tempco measurementI measured the temperature coefficient of my PDVS2mini v2. Already when measuring warm-up behaviour, it looked like that temperature had most influence on the PDVS2mini v2 output voltage. So i wanted to take a closer look.I put the PDVS2mini in a cooky tin. This cooky tin has wooden bars glued to bottom and sides. So the is content kept on a distance from bottom and walls.Also in the cookie tin is a LM35 temperature sensor for measuring the ambient temperature.IMG_4527_PSDVS2mini_v2_tempco_setup-2000pix.jpgThe cookie tin is placed in a cool box, with a 12V Peltier element and fan. It is placed in a way that the air can flow around it, but it is shielded from direct air flow from the fan. The cabling was also shielded / isolated from the air flow, to minimise thermal voltages.By reversing the power to the Peltier, one can also heat the contents of the cool box.Full size graph:PDVS2mini-v2-tempco-26-09-2025-1200pix.pngBlue is the ambient temperature. After some stabilizing time, the temperature goes down to ≈ 14°C. The temperature dwells at ≈ 14°C, to let the PDVS2mini internal temperature (and output) catch up. Then the temperature rises slowly to ≈ 31°C. Unfortunately, by then the battery was almost empty... So I let the temperature dwell at this temp, to get nice stable internal temp and output voltage values.Green is the internal PDVS2mini temperature, tracking the ambient with a some delay.Red is the resulting output voltage of the PDVS2mini v2. One vertical division is 10uV = 1ppm.Battery intermezzoThe grey curve is the PDVS2mini v2 battery voltage. Unintended this measurement was also a battery test. The measurement started with fully charged EBL 6F22 batteries, and after 8:50 hours they were empty. Earlier then promised / expected.So I ran capacity tests on 2 EBL 6F22 batteries, and got ≈ 450mAh. I posted test & results in theEBL 9V battery topic.Back to tempcoEven though I could not complete my temperature sweep because of empty batteries, there is enough info to calculate tempco.Using the boxed method I calculate a tempco of -0,77ppm/°C related to the outside temperature.Related to the PDVS2mini internal temperature, I got a tempco of -0,89ppm/°CThis is the same measurement, transferred to Excel:Full size graph:PDVS2mini-v2-tempco-26-09-2025-Excel-1500pix.pngHere I have added two traces, showing the PDVS2mini output voltage with the tempco calculated out of it. For each trace, I nudged the tempco figure to get as flat lines as possible.The added light-blue trace is the PDVS2mini v2 output, with the ambient tempco calculated out of it. I found an optimum using -0,75 ppm/°C tempco.The reason that this line is not flat is the delay between a change in ambient temperature, and the resulting output change.The added light-green line is the PDVS2mini v2 output, with the tempco referred to the PDVS2mini internal temperature calculated out of it. This line is much flatter, because of the good coupling between internal temp and output voltage. With this correction of -0,9ppm/°C the PVDS2 mini v2 output would only deviate ±1ppm over the 15°C ….31°C temperature range!ConclusionsThe Tempco figures found with the boxed method correlate well with the figures found in the Excel graph.My findings in the warm-up measurement were correct: my PDVS2mini v2 output is more sensitive to temperature then expected.The bad news is that the tempco I found of -0,75 ppm/°C is much worse than the Wrytech spec of “Typically < 2 ppm across a 10K temperature change”.The good news is that the light-green trace in the Excel graph shows that it is quite possible to calculate this tempco out in the PDVS2 mini v2 software, and removing it from the output. The temp sensor is already there.This could be done in the next PDVS2 mini v2 firmware.....I will run a second tempco measurement to verify my findings.Regards, Gertjan.

author: IanJ
author_rank: Unknown
timestamp: October 03, 2025, 07:45:18 am
content: Good test. I wonder if you could make improvements though.1. If the tin is mostly sealed the air inside will stratify, I.e. temperature layering causing issues, especially since the PDVS2mini generates heat itself.2. If going below ambient the tin may condensate causing temperature and humidity issues.I think changing out the tin and using a different material to barrier from direct airflow would be better.Here's my home made test chamber, removal door same material.I draped a thin cloth over the PDVS2mini. The peltier fans on the inside are very small so little airflow, just enough to move the air around to try and avoid gradients.Ian

author: Andreas
author_rank: Super Contributor
timestamp: October 03, 2025, 08:12:16 am
content: Hello,a diagram with internal temperature as x-axis would be interesting.And also if there is a difference between ramp up vs. ramp down (to see wether there is any hysteresis).with best regardsAndreas

author: Gertjan
author_rank: Frequent Contributor
timestamp: October 03, 2025, 08:37:01 am
content: Quote from: IanJ on October 03, 2025, 07:45:18 amHi Ian,Good points.I must admit that I used the cookie tin, because I use it for more shielded measurements. (The tin is connected to the guard of the 3458A)It is always good to consider imperfections in ones measurement setup, especially when results are different from expected.1 Re stratification: The LM35 ambient temperature sensor was at the same height (about the middle of the PDVS2mini box), and positioned that it would not be influenced too much by the PDVS2 temp, and also not too close to the cookie tin wall.2 The temperature changes were very slow (taking 2 hours to go from 20,7°C to 14°C). So I do not think condensation occurred.Risk of condensation was the reason I did not want to go any colder. Maybe next time I should also put a humidity sensor in the box.I already did a second measurement, with even slower temperature changes. I hope to post the results later today.regards, Gertjan.

author: Gertjan
author_rank: Frequent Contributor
timestamp: October 03, 2025, 08:45:09 am
content: Quote from: Andreas on October 03, 2025, 08:12:16 amHi Andreas,Indeed,a diagram with internal temperature as x-axis would is interesting, and I make them of every tempco measurement.I choose not to present them this time because the measurement sweep did not return to the starting temperature, and thus this plot is less informative.Meanwhile I did a second measurement, with a full sweep, and I will show these diagrams. Hopefully later today.regards, Gertjan.

author: Gertjan
author_rank: Frequent Contributor
timestamp: October 03, 2025, 03:00:39 pm
content: 2nd PDVS2mini v2 Tempco measurementI did a second tempco measurement, using the experience gained from the first. (But unfortunately before Ians ideas for improvement)Now the PDVS2mini v2 was powered externally, so no battery problems. The PDVS2mini was switched on the evening before, so the batteries were fully charged, and extra warmth of the charging was gone long before the measurement started.This time the temperature changes were even slower, so the PDVS2mini internal temperature could track the ambient better. And at the top and bottom temperatures I let the temperature dwell extra long, until PDVS2mini int. temp and output were stable too.Full size graph:PDVS2mini-v2-tempco-ext-ps-29-09-2025-1200pix.pngBlue trace is the ambient temperature. After letting everything stable for 30 minutes, the temperature goes slowly down in 2hours to 14.5°C. There it dwells for 1:20hour, until PDVS2mini internal temp and output are stable too.Then the temperature rises slowly, in 4hours to the maximum temp of 31.7°C. There it dwells again for 1:30hours, again until PDVS2mini internal temp and output are stable too.Then in 2hours back to the starting temperature. Unfortunately there was some overshoot. So, with power from the Peltier removed, I let it dwell towards an end temperature, with everything stable.Green is the PDVS2mini v2 internal temperature. It is lagging the ambient temp. One can see where the ambient temp is constant, that the internal temp needs about an hour to really catch up.And red is the output voltage of the PDVS2mini v2. As measured with the 3458A, and corrected with the calibration offset. Again one vertical division is 10uV = 1ppm.The same measurement in Excel:Full size graph:PDVS2mini-v2-tempco-ext-ps-29-09-2025-Excel-1500pix.pngI used the Excel table to calculate the boxed method tempco. Points were chosen near the end of the dwell periods, where all temps and output were stable.The result wasa box method tempco of -0,83ppm/°C related to the ambient temperature. Related to the PDVS2mini internal temperature, I got a tempco of -0,94ppm/°CThese values are close to the ones found in the first measurement.Also in the Excel graph are the additional traces with the tempco calculated outThe light-blue trace is where the Ambient tempco was calculated out of the output voltage. Best result I got with a nominal temp of 22°C, and a tempco of -0,8ppm/°CThe light-green trace is where the tempco referenced to the PDVS2mini v2 internal temperature was calculated out. Here the best result I got with a nominal temp of 29°C, and a tempco of -0,9ppm/°C. This got me a very flat line (<±1ppm deviation, and very close to the nominal 10V output.These tempco values are close to the boxed method values.Another look at the tempco is plotting the PDVS2mini output against temperature. This is for the tempco referenced to the ambient temperature:Full size graph:PDVS2mini-v2-tempco-ext-ps-29-09-2025-Ambient-1500pix.pngBlue is the PDVS2 mini v2 output plotted against ambient temperature. Ideal would be a straight line. If tempco would be zero, a horizontal line. If the tempco would be non-linear, the line would not be straight (but a curve, or even more complex)Here we see clearly that the output voltage is lagging the ambient temperature: it is shown by the distance between the the ascending and descending lines in the graph.A good thing is that the beginning and ending are meeting: there is no long term hysteresis (a more permanent shift in output after the temperature changes)Light-blue is the same plot, but with the tempco calculated out of it. This should be as horizontal as possible. I use this to judge if my tempco calculation was correct.Here is the same graph, but this time the tempco referenced to the PDVS2mini internal temperature:Full size graph:PDVS2mini-v2-tempco-ext-ps-29-09-2025-Internal-1500pix.pngImmediately we see that the ascending and descending lines are now much closer: Less hysteresis, the coupling between the internal temp and output voltage is much better.The line is straight: only first order tempco. Good!Beginning and end of the line are close together: no long term term hysteresis. Also good!The light-green line, with the tempco related to the internal temp calculated out of it, is more like a horizontal line. Showing that the tempco calculation was correct.ConclusionsWithout the pressure of battery time, I was able to do a slower temp sweep. With longer dwell times resulting in a more reliable boxed method tempco calculation.Starting and stopping at the same temp made (the absence of) long term hysteresis visible.The found tempco figures maching pretty good with the results of the first measurement, strengthening confidence.But the last graph, showing the tempco referenced to internal temperature is in my view the most important one.It shows clearly that, although the existing tempco is higher then expected, it is linear (first order), and good coupling between temperature and output.This means that the tempco could be calculated out of the output by the PDVS2 mini v2 firmware. It would result in a big improvement: in a 15°C temperature range output deviation would decrease from about 12ppm to 1...2ppm. Meaning the last digit becomes a lot less temperature dependent, and thus more reliable.The PDVS2mini v2 is a good and useful reference as it is. I am happy with it. But it seems there is room for further improvement. If I were the designer, I would be very tempted to further improve an already very good device...regards, Gertjan.

author: IanJ
author_rank: Unknown
timestamp: October 04, 2025, 12:05:56 pm
content: Certainly possible to adjust the cal map in the PDVS2mini based on temperature and see a more accurate output relative to tempco.......however, the issues would be:This complicates calibration during production.At a guess, each PDVS2mini wouldn't necessarily have the same swing in output for a given temperature change......so this would require in order to get it spot on for each and every PDVS2mini to calibrate during production at least 2 different temps, a min and a max and map from there.The hope of doing this would have to be testing a bunch of PDVS2mini's in a chamber, and from completely different batches. If they differ then this whole approach falls apart.Another issue could be the cal map changing as the temperature changes.....and if you were logging or doing something critical then you'd see a jump in output. The way around this could be to only switch maps on restart of the PDVS2mini......but I guess that kinda self defeats the whole thing.At the end of the day, IMHO, I'd leave it as is and only try to improve tempco at a hardware level.PS. PDVS2mini and PDVS2mini V2 differ. I don't have a V2 so can't comment (I've been asked).Great idea though!Ian.

author: aronake
author_rank: Frequent Contributor
timestamp: October 04, 2025, 02:48:57 pm
content: I proposed investigating temperature dependent calmapping earlier in this thread.How i would to it would be one set of parameter for sat 17 degrees, one for 23 degrees and one for 28 degrees. Then do cubic interpolation depending on actual temperature. And either have a separate temp sensor for ambient temp or use the internal and use delta temp to figure out ambient temp or something. Then there would not be jumps for different temperatures. And an option in the settings to just use the 23 degree cal map or this temp interpolated cal map.There are quite some complexities, but also seems rather doable and may or may not work, and may be tricky to verify, but could also be a cheap way to get away with TC compared to tweaking components.

author: Gertjan
author_rank: Frequent Contributor
timestamp: October 04, 2025, 05:33:16 pm
content: Quote from: IanJ on October 04, 2025, 12:05:56 pmHi Ian (and aronake),Interesting ideas & comments on tempco correcting the PDVS2mini v2.Extra interesting to hear the thoughts of the original developer.Indeed I do not think that compensatingeachPDVSmini v2 for it’s optimum tempco would be a good idea. It is just too impractical in production.But compensating the PDVS2mini v2 with anaveragetempco correction seems very well possible.Measure a few, and compensate all with the average. Even if it only would reduce influence of temperature to half or a third, it would be very worthwhile.I am thinking of a simple correction. The tempco is linear / first order. So no complicated corrections needed. In my Excel I used this simple formula:Output + (nominal temp – internal temp) * tempco coefficient = corrected output.You can download my original Excel sheethereif you want to play with it.Why do you think this will complicate calibration?I think you can calibrate with the correction in place. After all, if calibrating at the nominal internal temperature, the correction will do nothing.But maybe I am missing things, and is my solution too simple. And of course, when tempo is reduced, other sources of errors will become dominant. I can not judge that.I agree that improving at a hardware level is always the best idea.Of course I measured only one sample. Wrytech’s findings for the v2’s tempco are better than mine. So it is also possible that there is a hardware difference between mine, and the one measured by Wrytech.Maybe another brand resistors with worse tempco was used in production then for the measured prototype, etc.In the end the PDVS2mini v2 is now a commercial product of Wrytech. It is up to them what to do with this info.I just wanted to give them a nudge.Regards, Gertjan.

author: wrytech
author_rank: Contributor
timestamp: October 04, 2025, 11:29:51 pm
content: Nice to see the detailed measurements and effort put in by Gertjan, and the resulting discussion! Much appreciated, as any further testing adds to the standing of the units.I did, of course, think about adding some active tempco compensation logic around the temperature sensor included in all wrytech units. The main problem there is the Differential Nonlinearity (DNL) of the DAC, making the adjustments done by a compensation logic not perfectly predictable and possibly leading to unwanted results. One solution would be to measure the exact change in output voltage above and below the calibration points by a couple of counts each. The actual change in voltage will differ in practice from the nominal ~10 µV, and with this information a predictable compensation of the tempco could be done — at the cost of making the calibration more complex due to the amount of additional information needed, and the approach only works for the exact calibration points. Additionally, this should be paired with an individual measurement of the tempco for each unit, further adding to the work to be done.Quote from: Gertjan on October 04, 2025, 05:33:16 pmAs described in the blog post, I used the measurements of the three version 1.x units to check whether my measurements matched those done with the prototype by xDevs (thus verifying my test setup to some extent), which was the case, so I went on with testing the prototypes of v2. The v2 design has gone through multiple iterations, with some measuring worse in the absolute tempco and/or in the distribution among prototypes tested. So I have seen some worse results as well with the temperature chamber setup and found that Ian’s initial design is already very close, and changes to the critical parts of the design might not lead to improvements in practice (no matter how good they look on paper). The three units tested for v1 and the final v2 are not a large sample size; however, the results are close for each version, so I went ahead here.A point I would like to stress is that I built only three of the final v2 units initially, burned them in, and did the testing as shown in the blog post. No further selection for good or closely matching units was done for either v1 or v2. The same goes for the components used — the exact same ones were used for all v2 (and v1.6) units sold, with no changes made for worse-specced parts or similar. I am very cautious here, as not only the absolute tempco is important, but also the matching of the tempco, so without further measurements (that I really do not want to do) I would not make any changes.QuoteWhich, again, is much appreciated. I have been quite busy in the last weeks with the day job and private matters, and have been working on implementing SCPI-style commands as an additional possibility for remote control, also suggested by Gertjan. Once the firmware is tested, new units will ship with it directly, and it will also be made available on the website so users can update their existing v2 units themselves.Not committing to a timeline, but I will also implement an optional, experimental active tempco compensation function in firmware, available for anyone who wants to measure the tempco and experiment with adjustments. As long as this stays in firmware, it doesn’t require much additional effort on my side, but it could provide some interesting insights for everybody.Overall, I think — and testing for v2 has shown — that the reference is the limiting factor, and any further gains in hardware would come at significant cost and effort for testing.So, a lot of interesting directions to explore in the coming winter days, I would say.Best,Johannes

author: Gertjan
author_rank: Frequent Contributor
timestamp: October 05, 2025, 10:33:39 am
content: Hi Johannes,Good to see you back in this topic. I know you are extremely busy.Thank you for sharing background information and your thoughts.I think that individual measurement of tempco as part of calibration can not be expected at this price point.Quote from: Gertjan on October 04, 2025, 05:33:16 pmAfter readingthis post by branadic, I was expecting that the circuits after the reference (DAC etc.) were diluting the ADR1399 tempco.However, reading the ADR1399 datasheet again more carefully, the differences in our measurements could just be different ADR1399 samples. The headline spec is 0.2 ppm/℃. But the graphs are showing tempco’s between +0.44 ppm/℃. and -0.66 ppm/℃.one example:ADR1399-datasheet-tempco-1000pix.png(I do not know whether you are using the TO-46 or the LCC version)So the difference could just be a different ADR1399. With mine being a bit of an outlier.And you could very well be right:Quote from: wrytech on October 04, 2025, 11:29:51 pmRe component choices:Quote from: wrytech on October 04, 2025, 11:29:51 pmGood to hear that you are careful and cautious! Indeed it is easy to try to improve on one point, and find out later that something else got worse. Tempco is just one aspect, linearity and long term stability are important others.Quote from: wrytech on October 04, 2025, 11:29:51 pmI think this is an excellent idea, to make tempco compensation optional in software!This will not require more calibration effort, nor add BOM cost. So no increase of selling price for people who do not need the feature.And those that like the extra accuracy gained by tempco compensation can do their own measurements and adjustment. (The increase in cost is now their own time)I certainly will use it!Commercially, it is a good way to add a selling point to your product.QuoteNice to hear that you picked up this suggestion! I will update the TestController driver when the new firmware is published.Best regards, Gertjan.