Hello, My name is Lars Walenius and I live in Sweden. I am new to this forum but a volt nut for decades. I must admit I have to many DIY voltage reference boxes. Some years ago I was fortunate to work with Joe Geller on the SVR-T. For me the SVR-T still is the best 10V hobby reference sold. So it is a pity the AD587LQ isn´t available any more as my opinion is that the reference IC is the most important in a DIY reference. I can just second what Andreas say. Maybe the comment about metal cans need to be commented. Metal cans are good for humidity but I have seen high long term drifts on LT1031 that I have several powered on for years. Also if power is off for a or two month they go back many ppms. On REF102CM in metal cans (obsolete) I have seen about 5ppm if turned off a longer time. In the same test AD587LQ (obsolete) changed less than a ppm. AD587JQ and AD587UQ are still available but I would not recommend the UQ as my and others observations are in the 10ppm/C class ( probably due to adaption to a very wide temp range). I have several JQ with reasonable (less than 5ppm/C that can be compensated with NTC) but you should check noise (LF). I have seen several ppm p-p on some. So by selection I think the AD587JQ is the best 10V ref available today (from eg Digikey). Charles, I have to say thank for all your good comments both here and in time nuts but if the 130USD ref is the D105 on Ebay have a look on EEVBlog and my humidity tests. The 2ppm ref has 20ppm drift for a change 40 to 90%RH in just a week!! http://www.eevblog.com/forum/testgear/calibratory-d-105-dc-precision-voltage-reference-standard/630/ Lars Från: Russ Ramirez Skickat: ‎tisdag‎ den ‎24‎ ‎november‎ ‎2015 ‎15‎:‎29 Till: Discussion of precise voltage measurement Thank-you all for your valuable insights and the book reference Jahn. I can see clearly now that doing such a project with a LM399 for example as a learning project would be interesting. Designing the board to use the MAX6126, and finding reasonably priced low tempco parts was a useful exercise. Russ On Tue, Nov 24, 2015 at 5:55 AM, <acbern@gmx.de> wrote: > There are many things to factor in. Drift of reference itself over time > and temperature (399 is 1ppm/K worst case alone, over say 10K, i.e. > 23C+/-5K). Drift of the gain setting resistor is critical (assuming you > have an amp generating 10V out of the 399 output voltage). and so on. > Also, you need a precise reference to calibrate the units (low cal > uncertainty and low drift). > Selection, statistical validation and aging is needed. > All doable but costly and more complicated than one might expect. > > Thats why I think the target price has to be reasonable, any thoughts here? > > > > > > Gesendet: Dienstag, 24. November 2015 um 10:05 Uhr > > Von: "Ian Johnston" <ian@ianjohnston.com> > > An: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > > Betreff: 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. > > > > Hmmmm! > > > > Ian. > > > > > > > > -----Original Message----- > > From: acbern@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" <csteinmetz@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 > > > > > > > > > _______________________________________________ > > > 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. > > > > > > > > > > [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 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.

Wow, there's a ton to know about NTC thermistors by themselves! Lars, is the part for the Geller style of unit similar to this one, ( http://www.digikey.com/product-detail/en/NXRT15XH103FA1B030/490-8601-ND/3788625) or very different? Russ On Tue, Nov 24, 2015 at 8:51 AM, Lars Walenius <lars.walenius@hotmail.com> wrote: > Hello, > > > My name is Lars Walenius and I live in Sweden. I am new to this forum but > a volt nut for decades. I must admit I have to many DIY voltage reference > boxes. Some years ago I was fortunate to work with Joe Geller on the SVR-T. > For me the SVR-T still is the best 10V hobby reference sold. So it is a > pity the AD587LQ isn´t available any more as my opinion is that the > reference IC is the most important in a DIY reference. > > > I can just second what Andreas say. Maybe the comment about metal cans > need to be commented. Metal cans are good for humidity but I have seen high > long term drifts on LT1031 that I have several powered on for years. Also > if power is off for a or two month they go back many ppms. On REF102CM in > metal cans (obsolete) I have seen about 5ppm if turned off a longer time. > In the same test AD587LQ (obsolete) changed less than a ppm. AD587JQ and > AD587UQ are still available but I would not recommend the UQ as my and > others observations are in the 10ppm/C class ( probably due to adaption to > a very wide temp range). I have several JQ with reasonable (less than > 5ppm/C that can be compensated with NTC) but you should check noise (LF). I > have seen several ppm p-p on some. So by selection I think the AD587JQ is > the best 10V ref available today (from eg Digikey). > > > Charles, I have to say thank for all your good comments both here and in > time nuts but if the 130USD ref is the D105 on Ebay have a look on EEVBlog > and my humidity tests. The 2ppm ref has 20ppm drift for a change 40 to > 90%RH in just a week!! > > > > http://www.eevblog.com/forum/testgear/calibratory-d-105-dc-precision-voltage-reference-standard/630/ > > > > > > > Lars > > > > > > > Från: Russ Ramirez > Skickat: ‎tisdag‎ den ‎24‎ ‎november‎ ‎2015 ‎15‎:‎29 > Till: Discussion of precise voltage measurement > > > > > > Thank-you all for your valuable insights and the book reference Jahn. I can > see clearly now that doing such a project with a LM399 for example as a > learning project would be interesting. Designing the board to use the > MAX6126, and finding reasonably priced low tempco parts was a useful > exercise. > > Russ > > On Tue, Nov 24, 2015 at 5:55 AM, <acbern@gmx.de> wrote: > > > There are many things to factor in. Drift of reference itself over time > > and temperature (399 is 1ppm/K worst case alone, over say 10K, i.e. > > 23C+/-5K). Drift of the gain setting resistor is critical (assuming you > > have an amp generating 10V out of the 399 output voltage). and so on. > > Also, you need a precise reference to calibrate the units (low cal > > uncertainty and low drift). > > Selection, statistical validation and aging is needed. > > All doable but costly and more complicated than one might expect. > > > > Thats why I think the target price has to be reasonable, any thoughts > here? > > > > > > > > > > > Gesendet: Dienstag, 24. November 2015 um 10:05 Uhr > > > Von: "Ian Johnston" <ian@ianjohnston.com> > > > An: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > > > Betreff: 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. > > > > > > Hmmmm! > > > > > > Ian. > > > > > > > > > > > > -----Original Message----- > > > From: acbern@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" <csteinmetz@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 > > > > > > > > > > > > _______________________________________________ > > > > 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. > > > > > > > > > > > > > > > [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 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. >

Hello Lars, or course you are right: the AD587 (10V) and AD586 (5V) are the best (unheated) chips with hermetically package today. I think they would be even perform better with a metal can housing, since the mechanical decoupling from PCB forces (e.g. from humidity) is better from principle for the TO-99 package. (at least if you let the legs quite long). But of course the mechanical decoupling can be done also by some other way. with best regards Andreas Am 24.11.2015 um 15:51 schrieb Lars Walenius: > Hello, > > So by selection I think the AD587JQ is the best 10V ref available today (from eg Digikey). > > > Lars >

Andreas wrote: >Hello Lars, or course you are right: the AD587 (10V) and AD586 (5V) >are the best (unheated) chips with hermetically package today. I'm curious why you think the AD587/586 are better than other hermetically packaged references with better drift and noise specifications -- in particular, MAX6350MJA AD588KQ LTC6655CHLS8 LTC6655BHLS8 REF102CM (see attached table). (Note that the hermetic version of the MAX6350 has a 2.5ppm/C drift spec, not 1ppm/C as listed in the table for a different package.) The 587 has a better long-term drift spec than the 6360 and the 6655 (but note that the 587 is 3x worse than the REF102 in this regard). To my mind, the better tempco and noise of the 6350 and 6655 outweigh the better long-term drift of the 587 in an overall ranking. Best regards, Charles

Hi all, Just a note: On my own project, I had used the MAX6350 in the prototype and the major downside for me was the thermal hysterysis it had. Then again, I had mounted a small crystal heater on top of it (set to 32degC +/- 0.1degC)......and I was pushing the limits as I was trying to resolve down to 38uV on a 0-10Vdc range using the 6350 as the 18bit DAC's 5V ref. Ian. -----Original Message----- From: Charles Steinmetz <csteinmetz@yandex.com> To: Discussion of precise voltage measurement <volt-nuts@febo.com> Date: Wed, 25 Nov 2015 06:17:07 -0500 Subject: Re: [volt-nuts] Low-cost voltage reference questions Andreas wrote: >Hello Lars, or course you are right: the AD587 (10V) and AD586 (5V) >are the best (unheated) chips with hermetically package today. I'm curious why you think the AD587/586 are better than other hermetically packaged references with better drift and noise specifications -- in particular, MAX6350MJA AD588KQ LTC6655CHLS8 LTC6655BHLS8 REF102CM (see attached table). (Note that the hermetic version of the MAX6350 has a 2.5ppm/C drift spec, not 1ppm/C as listed in the table for a different package.) The 587 has a better long-term drift spec than the 6360 and the 6655 (but note that the 587 is 3x worse than the REF102 in this regard). To my mind, the better tempco and noise of the 6350 and 6655 outweigh the better long-term drift of the 587 in an overall ranking. Best regards, Charles [Sent by MDaemon Mail Server at IanJohnston.com]

Hello, MAX6350MJA is unobtanium today All you can get on the market in small quantities are fakes. The plastic parts that I have drift all around 10ppm/year (30 ppm in 3 years) Further at least some of the MAX6350/6250A parts have some kind of "popcorn noise" REF102CM is also no longer produced The plastic parts suffer from humidity with several ppm drift. AD588KQ should behave similar to the other AD58* devices. But I do not consider this as "low cost". The LTC6655 is a bandgap -> from principle less stable. I have measured a large thermal hysteresis (6 ppm) for a +/-15 deg C temperature excursion around room temp. with a LTC6655AILS8-5. In practical use the 1/f noise is not lesser than on a AD586. (measured 2.7uVpp) The long term drift spec in the datasheets are only "typical values" for the first 1000 hours. So have nothing in common with a 1year spec. Also the tempco values are usually for the whole temperature range. On many reference types (not all) the tempco at the range limits increases. (that explains the MAX spec for the military temperature range) On some references the near 25 deg C temperature gradient is much lesser. For the AD586LQ I have measured 23 out of 29 samples better than 1ppm/K at 25 deg C. with best regards Andreas Am 25.11.2015 um 12:17 schrieb Charles Steinmetz: > Andreas wrote: > >> Hello Lars, or course you are right: the AD587 (10V) and AD586 (5V) >> are the best (unheated) chips with hermetically package today. > > I'm curious why you think the AD587/586 are better than other > hermetically packaged references with better drift and noise > specifications -- in particular, > > MAX6350MJA > AD588KQ > LTC6655CHLS8 > LTC6655BHLS8 > REF102CM > > (see attached table). (Note that the hermetic version of the MAX6350 > has a 2.5ppm/C drift spec, not 1ppm/C as listed in the table for a > different package.) > > The 587 has a better long-term drift spec than the 6360 and the 6655 > (but note that the 587 is 3x worse than the REF102 in this regard). > To my mind, the better tempco and noise of the 6350 and 6655 outweigh > the better long-term drift of the 587 in an overall ranking. > > Best regards, > > Charles > > > > _______________________________________________ > 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.

On 25 Nov 2015 11:18, "Charles Steinmetz" <csteinmetz@yandex.com> wrote: > > I'm curious why you think the AD587/586 are better than other hermetically packaged references with better drift and noise specifications -- in particular, > > MAX6350MJA > AD588KQ > LTC6655CHLS8 > LTC6655BHLS8 > REF102CM > > (see attached table). Your table mentions at the bottom the LTZ1000, but you don't have that device listed in the table. I assume that is an oversight, but perhaps it was intensional. As regards humidity, I wonder if an reasonable attempt at sealing a package combined with silica gel inside would give an internal humidity that keeps fairly stable. I recall seeing a mix of chemicals on eBay that were a calibration standard for humidity. I assume that if one got some hermetically sealed feedthrough caps, it would not be hard to put a PCB inside a tinplate box that's soldered along each edge to form a hermetically sealed container. Then one would have a sealed environment. I can imagine it would be desirable to flush out all solder fumes before making a final seal. Maybe the flux residuals that I expect outgas over time would cause more problems than it solves. Note that I have never worked on anything requiring such sealing, so I would not be surprised if someone who has worked on such products would laugh at my suggestions! I note that Schott appear to produce hermetically sealed enclosures. I would have thought it practical to build electronics at home where changes of humidity over time could be virtually eliminated. But I have no experience in this subject. Dave.