Ian Johnston PDVS2

[kj7e]

Just pulled the trigger, the waiting begins...

http://www.ianjohnston.com/index.php/onlineshop/handheld-precision-digital-voltage-source-v2-detail

[tautech]

Did you know Ian is a member here ?
https://www.eevblog.com/forum/profile/?u=4754

Probably a thread about his reference somewhere in the forum.

[kj7e]

I figured he must be    I didn't see anything here regarding V2 with the LM399, but I likely just didnt search hard enough.

[IanJ]

I am here.....

Ian.

[tggzzz]

I notice that the units are burned in for 48 hours. Is there any indication that it is unnecessary to have a longer burn-in period, say 1 week to 1 month?

Background: my limited experience, with a different reference, is that noticable changes occurred over more than 168 hours.

[IanJ]

I notice that the units are burned in for 48 hours. Is there any indication that it is unnecessary to have a longer burn-in period, say 1 week to 1 month?

Background: my limited experience, with a different reference, is that noticable changes occurred over more than 168 hours.

In the first 12hrs I see the output vary on some units (but not all) but then start to settle.

I found that the power cycles, i.e. temperature cycling has more of an initial effect on settling the initial output. On the very first prototype (that Dave saw in his mailbag) the reference used there was reasonable.....until you started the power/temperature cycles......it never powered up twice with the same output. The LM399AH is completely different.

There is also a full battery charge cycle from flat to full on every unit which helps.

But also it's down to the fact I am building & selling these in my spare time and 48hrs fit my production line. Also, given that the user can recalibrate themselves I have never been overly concerned with anything more than 48hrs.
There is a spec for the unit I try to adhere to, anything else is a bonus........but I do read LM399AH's can take a long time to settle (months!) going by what others say..........i'd love to know what other manufacturers do in terms of burn-in times of their LM399AH based units.

I use low tempco resistors around the LM399AH and final output, and making use of some nice LTC2050HV & LTC1250 chopper op-amps.
The DAC itself is the 18-bit DAC9881 from TI........I haven't found anything better.

PS. One thing I have learned........my 3458a is the dogs b******s, whilst my Keysight 34461a doesn't have a great tempco.....I can almost tell the temperature in my workshop using the 34461a and the uV variances.

Ian.

[tggzzz]

But also it's down to the fact I am building & selling these in my spare time and 48hrs fit my production line.

Understood and accepted. If I was doing something like this I think I would buy 10, keep them continuously powered in a test jig, remove 1 at a time when an order arrived and replace it with a new order. Obviously there is an decision about whether to have 10, or 20, or 30 etc

Also, given that the user can recalibrate themselves I have never been overly concerned with anything more than 48hrs.

Always presuming they aren't using this as their primary reference!

PS. One thing I have learned........my 3458a is the dogs b******s, whilst my Keysight 34461a doesn't have a great tempco.....I can almost tell the temperature in my workshop using the 34461a and the uV variances.

I certainly can using my Solartron 7081 and saturated Weston cells But they (+ the 7081) have the advantage of being slightly less noisy than my Trancell.

[TiN]

PS. One thing I have learned........my 3458a is the dogs b******s

I'm not sure I understand this section, could you elaborate?

[Wytnucls]

http://www.urbandictionary.com/define.php?term=Dog%27s%20Bollocks

[TiN]

Alrightie. English ain't my native, have mercy

[kj7e]

Wow, that's all I have to say right now.  Super impressed, thanks Ian!

[IanJ]

Great stuff!........always good to see the unit in somebody else's hands.

Ian.

[kj7e]

Great stuff!........always good to see the unit in somebody else's hands.

Ian.

Running some tests, more stable and lower noise than the LT1021 based reference.  Took me a min to figure out how to move the courser under the digit for the rotary encoder (had to read the manual haha).

[mimmus78]

Ian

Great work!
May I ask you how much you spent for the CE stuff?
Do you apply it only for EMC or also something from the T&M part?

[IanJ]

Ian

Great work!
May I ask you how much you spent for the CE stuff?
Do you apply it only for EMC or also something from the T&M part?

So, I wanted to sell the PDVS2 legally in the UK/EU.......so went looking into CE but found it a minefield. So, I employed the services of Barclay Phelps and was quoted 500UKP but needed a 2nd directive not initially anticipated so total cost 765UKP.
For that I got the technical file including the DoC (in my case EMC, RoHS & EN61326-1-2013 conformity statements).
Then all I had to do was buy the stickers....:-)

Ian.

[kj7e]

Ian,  I did notice the PDVS2 is somewhat sensitive to orientation.  That is, if you tilt it up at an incline say 45 deg to better see the display, the voltage will drop maybe 50uV from 10V.  I suspect warm air around the LM399 is affecting nearby components and at an angle the this slightly disrupts the normal heat distribution pattern. Not a big deal, but I found it interesting.  Have you seen the same?

[Andreas]

Hello

all LM399 are sensitive to orientation (some more and some less).

my K2000 had around 8.4 ppm on tilting

https://www.eevblog.com/forum/metrology/project-pimp-a-keithley-2000/

And I have access to a further K2000 which changes readings even in the range of 20 ppm.
So your 5 ppm are not unusual.

You can improve that (partly) when thermally isolating the LM399.
(from both sides of the PCB -> also the soldering joints).

Of course that may also affect calibration.

with best regards

Andreas

[IanJ]

Ian,  I did notice the PDVS2 is somewhat sensitive to orientation.  That is, if you tilt it up at an incline say 45 deg to better see the display, the voltage will drop maybe 50uV from 10V.  I suspect warm air around the LM399 is affecting nearby components and at an angle the this slightly disrupts the normal heat distribution pattern. Not a big deal, but I found it interesting.  Have you seen the same?

Hi,

Yes, a phenomenon of the LM399, and I have tried to minimize it's effects with holes in the pcb around the LM399 to help thermally isolate it.
I do see the odd unit which does appear to not budge hardly at all in terms of orientation, but unfortunately it's not something that can be specified at order and it's not something I considered measuring and characterizing.
I have two workshop units I use and one is about the same as yours, the other about 20uV.......but all within spec. for the unit.

Not sure if you are running of external DC or batteries, but batteries are the most recommended method of power source. More predictable thermals amongst other factors.

Ian.

[Andreas]

Hello Ian,

which raw voltages do the both references have?
I suspect that the effect is related to the unheated tempco of the LM399.

So LM399s which are closer to 6.875V should be affected less.

with best regards

Andreas

[kj7e]

Ian,  I did notice the PDVS2 is somewhat sensitive to orientation.  That is, if you tilt it up at an incline say 45 deg to better see the display, the voltage will drop maybe 50uV from 10V.  I suspect warm air around the LM399 is affecting nearby components and at an angle the this slightly disrupts the normal heat distribution pattern. Not a big deal, but I found it interesting.  Have you seen the same?

Hi,

Yes, a phenomenon of the LM399, and I have tried to minimize it's effects with holes in the pcb around the LM399 to help thermally isolate it.
I do see the odd unit which does appear to not budge hardly at all in terms of orientation, but unfortunately it's not something that can be specified at order and it's not something I considered measuring and characterizing.
I have two workshop units I use and one is about the same as yours, the other about 20uV.......but all within spec. for the unit.

Not sure if you are running of external DC or batteries, but batteries are the most recommended method of power source. More predictable thermals amongst other factors.

Ian.

I picked up some EBL Li-Ion 9v's as you recommended and found an 18v 1a wall wart on Amazon to use as a charger (guitar distortion pedal power supply), works quite well. 

[IanJ]

I picked up some EBL Li-Ion 9v's as you recommended and found an 18v 1a wall wart on Amazon to use as a charger (guitar distortion pedal power supply), works quite well.

That will will ok.......but just be aware if it is a switch mode power supply then it won't be the best and will inject a little HF noise into the system despite the dual filters on the psu circuit. However, if it's a linear psu then it'll be fine. Saying that, if you are just using it to charge the batteries then no problem.

Ian.

[IanJ]

So LM399s which are closer to 6.875V should be affected less.

Ahhhh, now that I didn't know!

Ian.

[Free_WiFi]

The Ian Johnston's unit is very ,very unique stuff around here (an unique piece of art in he's genre),but if we are talking about the hobbiest purposes then this unit become pretty dead....
I will give my money for it,but only in the case if this unit would be able to do more ,like: µA,mA .
Who knows the future
maybe something like that is coming from the Ian Johnston's horizonts or maybe from something else

[Gyro]

You are reading and posting in the Metrology section here - it is about highest achievable precision, not hobbyist DMMs level.

For Hobby DMMs you would be better to look in the Beginners or Test Equipment sections. 

[Free_WiFi]

You are reading and posting in the Metrology section here - it is about highest achievable precision, not hobbyist DMMs level.

For Hobby DMMs you would be better to look in the Beginners or Test Equipment sections. 

I feel some kind of hostility smell against me,but why ?
Im just getting out my personal opinions.
In my opinion this device is very expensive without functions like µA,mA and + you're super pathetic if you really wanna tell me that this is some kind of professional instrument for calibration or reference ... 
I don't think and i also won't to believe that a real professionals will use this expensive black box toy in the real professional fields of metrology ... 
So please... keep kalm and love your toys ,im also not blaming someone or something ,this black magic box is still pretty cool,but damn !!! is very expensive and of course is not for professional purposes like you are trying to make me to believe in it