Re: [volt-nuts] LTZ1000 project build
Hi, The product I designed to use the 2ppm/degC resistors is sealed in an enclosure where the LM399AH etc live, so I don't expect much problem with humidity. I use 2K2, 3.3K, 10K & 22K. It's the RG2012L series from Susumu:- http://datasheet.octopart.com/RG2012L-103-L-T05-Susumu-datasheet-13139546.pdf http://www.susumu.co.jp/common/pdf/n_catalog_partition01_en.pdf The 2nd PDF above is mainly for the 5ppm versions but does contains various graphs including humidity. Ian. On 03/06/2016 17:01, Lars Walenius wrote: Hi, Do you have any idea of the aging and humidity sensitivity of these 2ppm/C resistors? I have tested many resistors during the years and my opinion is that tempco is not the biggest problem for normal nuts use but of course may be if you sell a product. For a nut it is quite easy to check the tempco but not aging and humidity sensitivity. Of the resistors I have tested it is only hermetical sealed resistors that I don´t see a humidity sensitivity on. Even if they are bulk metal foil, wire wounds or metal films with low tempco´s they seem to have very varying humidity sensitivity if not sealed. Lower values of resistance (100-1k) normally seems to be better than 10-100kohm values that in all families may have up to 1-2ppm/%RH. Last year I bought wire wounds, to be used in a LTZ1000 based design, that were supposed to be insensitive to humidity but they were not. They were even worse than other brands of WW and had several months of time constant. After a while the manufacturer admitted that it was a problem in the manufacturing and they were humidity sensitive. So far I haven´t received a replacement. Of course if you have a resistor with 2ppm/%RH and a seasonal variation of 50%RH it is only maximum 1ppm seasonal variation on the output on the LTZ. That is not easy to measure for most of us nuts. Lars Från: i...@ianjohnston.com<mailto:i...@ianjohnston.com> Skickat: den 26 maj 2016 13:35 Till: il...@xdevs.com<mailto:il...@xdevs.com>; volt-nuts@febo.com<mailto:volt-nuts@febo.com> Ämne: Re: [volt-nuts] LTZ1000 project build Hi all, TiN, out of interest I spent ages fishing for low ppm/degC resistors for my own reference..ended up with 2ppm units from DigiKey. Yes, they are expensive and send the BOM into the clouds!..so I know how you feel! Ian. - Original Message - From: Illya Tsemenko [mailto:il...@xdevs.com] To: volt-nuts@febo.com Sent: Thu, 26 May 2016 18:42:54 +0800 Subject: [volt-nuts] LTZ1000 project build I'm glad my little project got so much attention. Worth to mention few points regarding my (or any other LTZ1000) unit: A. One should consider cost of whole BOM, not only LTZ chip. In my case resistors from VPG exceed cost of LTZ1000 by far. B. PCB I designed was targeted best to my own application need, where compact size and direct output (whatever is coming out of LTZ) were key importance. Since modules are part of bigger system with DAC synth, specific value, like 7.150 was not important for me. C. If there is large enough group to have this project going, I can actually modify original design (e.g. for easier hand soldering, or added buffer or ratio circuits, onboard LDO, you name it) and get PCBs made for interested nuts, at small cost. You can also find lot of temco/stability data with temperature/environment logs with mentioned LTZ modules on my site here: https://xdevs.com/services/ in LTZ1000 voltage reference tests section. RAW DSV data are available. I still have 3 modules at hand for any testing/checks (one was sold while ago, one was installed in HP 3245A source to replace LM399). Illya "TiN" Tsemenko ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. -- Ian Johnston www.ianjohnston.com https://www.youtube.com/user/IanScottJohnston /"Because it feels good to make stuff!"/ ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] LTZ1000 project build
Hi all, TiN, out of interest I spent ages fishing for low ppm/degC resistors for my own reference..ended up with 2ppm units from DigiKey. Yes, they are expensive and send the BOM into the clouds!..so I know how you feel! Ian. - Original Message - From: Illya Tsemenko [mailto:il...@xdevs.com] To: volt-nuts@febo.com Sent: Thu, 26 May 2016 18:42:54 +0800 Subject: [volt-nuts] LTZ1000 project build I'm glad my little project got so much attention. Worth to mention few points regarding my (or any other LTZ1000) unit: A. One should consider cost of whole BOM, not only LTZ chip. In my case resistors from VPG exceed cost of LTZ1000 by far. B. PCB I designed was targeted best to my own application need, where compact size and direct output (whatever is coming out of LTZ) were key importance. Since modules are part of bigger system with DAC synth, specific value, like 7.150 was not important for me. C. If there is large enough group to have this project going, I can actually modify original design (e.g. for easier hand soldering, or added buffer or ratio circuits, onboard LDO, you name it) and get PCBs made for interested nuts, at small cost. You can also find lot of temco/stability data with temperature/environment logs with mentioned LTZ modules on my site here: https://xdevs.com/services/ in LTZ1000 voltage reference tests section. RAW DSV data are available. I still have 3 modules at hand for any testing/checks (one was sold while ago, one was installed in HP 3245A source to replace LM399). Illya "TiN" Tsemenko ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] 8.5 digit DMM wanted
Hi all, Anyone have or know of a Keithley 2002 or HP 3458a for sale. Don't mind a faulty unit. Willing to pay worldwide delivery to UK. Ian. Ian at ianjohnston dot com Sent from my iPad [Sent by MDaemon Mail Server at IanJohnston.com] ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] LM399 & LM399AH
Hi all, Just wondered if anyone has experience of the A and non-A versions of the LM399. I.E. 0.3 - 1ppm max., versus 0.3 - 2ppm max. In reality, is it worth the extra cost for the 1ppm max. version.or in normal typical circumstances are they generally going to perform not as far apart? Thanks, Ian. [Sent by MDaemon Mail Server at IanJohnston.com] ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] LM399 selection test PCB
Hi, Sasumu RG2012L-223-L-T05 from Digikey - 408-1636-1-ND 0805 package. £2.90 each in low qty. My first experience of them... I was also trying 5ppm/degC resistors but they drifted like hell. I haven't done the sums yet so either the 2ppm ones are good, or the 5ppm ones aren't so good...there was too much drift to simply be 2 versus 5 ppm/degC. The jumps/noise one the one LM399 is every second...haven't investigated yet. Ian. On 26/11/2015 15:46, Lars Walenius wrote: Nice board! Will give you a lot of experience. See forward if you have more to report. What 2ppm/degC resistors do you use? Do you have any previous experience with them? Like noise , jumps could have its own thread. I think I have seen 5-10uV jumps on most of my 10V refs based on buried zeners. On some it has been years between and some very often. For some I have only seen it during temperature scans over a span of a couple of °C. Sometimes at low temperature and sometimes at higher temperatures. Of course the LM399 is special with its fixed heater. On one DMM based on LM399 I can have minutes or sometimes hours with 1.5ppm shift in reading but when it goes back for a long time. This have been ongoing for 20 years for that particular DMM. Lars Från: Ian Johnston Skickat: onsdag den 25 november 2015 23:29 Till: Discussion of precise voltage measurement Hi all, Thought you guys might be interested in a small PCB I made in order I could test, select & check pre-age (if there is such a thing!) my LM399's. 10 channel. Each channel has it's own chopper op-amp (self bias the LM399), 2ppm/degC tempco resistors throughout, 2x2 sockets for the LM399's (same footprint). Test points for each channel. Jumper link on the power rail to disable each channel individually (op-amp and heater power). Holes around each LM399 footprint to help isolate any thermal stress. Here:- http://www.ianjohnston.com/temp/lm399select.jpg So far it's working out great...i've already discovered one of my LM399AH's (sitting in ch.4 in the photo) is somehow unstable. It's output jumps around by about 10uV's. Need to investigate The idea is that I can test, select and pre-age LM399AH's before soldering them into my target PCB's. I understand that soldering can/will reset any aging...but I figured it might help. I did a pre-test on those Ebay LM399's I bought and they seem to work ok...still to properly evaluate.but I do notice that the new ones's I bought from Digikey are all giving over 7Vdc, the Ebay ones all well under 7Vdc. Cheers! Ian. -- Ian Johnston www.ianjohnston.com https://www.youtube.com/user/IanScottJohnston /"Because it feels good to make stuff!"/ [Sent by MDaemon Mail Server at IanJohnston.com] ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] LM399 selection test PCB
Hi all, Thought you guys might be interested in a small PCB I made in order I could test, select & check pre-age (if there is such a thing!) my LM399's. 10 channel. Each channel has it's own chopper op-amp (self bias the LM399), 2ppm/degC tempco resistors throughout, 2x2 sockets for the LM399's (same footprint). Test points for each channel. Jumper link on the power rail to disable each channel individually (op-amp and heater power). Holes around each LM399 footprint to help isolate any thermal stress. Here:- http://www.ianjohnston.com/temp/lm399select.jpg So far it's working out great...i've already discovered one of my LM399AH's (sitting in ch.4 in the photo) is somehow unstable. It's output jumps around by about 10uV's. Need to investigate The idea is that I can test, select and pre-age LM399AH's before soldering them into my target PCB's. I understand that soldering can/will reset any aging...but I figured it might help. I did a pre-test on those Ebay LM399's I bought and they seem to work ok...still to properly evaluate.but I do notice that the new ones's I bought from Digikey are all giving over 7Vdc, the Ebay ones all well under 7Vdc. Cheers! Ian. -- IanJohnston.com /"because it feels good to make stuff"/ [Sent by MDaemon Mail Server at IanJohnston.com] ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Low-cost voltage reference questions
Hi all,
I can relate to this...and only last night I was pouring over it
wondering what to do!
I have just designed a Handheld Precision Digital Voltage
Source.LM399AH & uController controlled.
About to start selling them, and so I am writing the manual & spec sheet for
it...but can't decide without a years worth of data & testing behind me
what figures to use!
I've got the reference, DAC and op-amp figures, all the tempo's I need etc
etc.
H!
Ian.
-Original Message-
From: acb...@gmx.de
To: volt-nuts@febo.com
Date: Tue, 24 Nov 2015 09:35:24 +0100
Subject: Re: [volt-nuts] Low-cost voltage reference questions
Charles and group,
another persons opinion:
I guess the reference to the "standards" means those sold on ebay US. If so,
I would think it is a false expectation this would meet 3ppm acc. guaranteed
within a year.
There is a lengthy chat in eevblog about it, in case you are not aware, and
while the unit typically may not be too bad, it is certainly not seriously a
3ppm guaranteed standard (even in its best version). It starts with the
traceability, and goes on with the design and build standard. Details in the
blog. In summary, it is not even really spec'ed, also because it can't be
(at least not close to what it seems to raise in expectations). But at that
price, it would be unfair to expect more than a hobbyist item with
relatively unclear real specs. But if you mean another item, let us know, I
guess the group would be interested.
Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year. There
is data available from Fluke about 732B drifts ("Predictability of Solid
State Zener References"), and it can be seen how hard it is for them to
guarantee 2ppm/year.
So I think your price target and spec expectation ("guaranteed to
remain"...) just does not match.
I would think a unit that has a traceable specification to a National
Standard (including an error propagation analysis for the factory
calibration how to get there), and be within say 5ppm a year, over a defined
(limited) temperature range, with a good build standard (CU-TE spades, metal
case, EMI filtering, PSU...), targeted at those who cannot afford/do not
need a 732B could easily have a fair price of a couple hundred usd.
Other opinions welcome.
Cheers
Adrian
> Gesendet: Montag, 23. November 2015 um 23:26 Uhr
> Von: "Charles Steinmetz" <csteinm...@yandex.com>
> An: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
> Betreff: Re: [volt-nuts] Low-cost voltage reference questions
>
> Russ wrote:
>
> >What is considered the break-over point of precision with low uncertainty
> >versus cost to a group like this? Is there a rule-of-thumb for the cost
of
> >each additional digit of precision after N digits?
>
> One person's opinion:
>
> To a group like this, I'd be inclined to say that interest begins at
> a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
> guaranteed to remain within 3ppm from 18-22C for at least one year
> after purchase). 3 ppm is 0.0003%. There is at least one 10v
> reference with specifications in this ballpark available at an asking
> price under $130 (I'm told the seller has accepted offers
> significantly lower than this).
>
> >If I sell someone a reference
> >that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty,
is
> >it valuable as a 0.1% reference even though the error may be much less,
> >like +/- 0.08%?
>
> I, for one, do not consider 0.08% to be "much less" than 0.1%. One
> sneeze and it's out of spec. Indeed, I would consider a claim of
> 0.1% accuracy to be bordering on fraudulent based on a calibrated
> measurement at 0.08%, unless the spec was qualified as "within 0.1%
> at [temperature within 0.1C] as is, where is -- no claim as to
> accuracy after it has been shipped to the buyer."
>
> Speaking as someone with substantial commercial design experience, I
> would never offer a voltage reference for sale as a claimed "0.1%
> standard" that I did not have excellent justification for believing
> would stay below 0.05% for a year over a several-degree range of
> temperature and multiple trips across the country via commercial
> carriers. I wouldn't expect to be able to charge more than $10-15
> for the product just described, and then only if the nominal output
> voltage were 10v (I think you will find that there is a very strong
> preference for 10v references over 5v, 2.5v, or other voltages).
>
> Best regards,
>
> Charles
>
>
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