Core Vref aging - what's reasonable to expect? Months, years, eons?  - Page 1
Forum section: electronics / general

author: Rax
author_rank: Super Contributor
timestamp: October 21, 2023, 12:01:04 am
content: There's a chat elsewhere on what's reasonable to expect in terms of references aging in old, medium age, and maybe new instrumentation. Or brand new DIY kits and whatnot.I am thinking of specifically core voltage references. LM199/299/399, SZA263s, LTFUs, LTZ1000As, all that stuff. Obviously, some may be ovenized, others not.My main bench equipment is pretty old - and for good reason, which is both affordability, and maybe even more importantly, because their references are well aged - but in other peoples' cases, this question will pertain to purchasing new chips and aging them intentionally before use for maybe hundreds, or thousands of hours. Anything I'm expecting to adjust I try to age as much as I can - and the fact that my projects sometimes extend over months helps (this is a hobby, mind you). For instance, I have an EDC thingie where someone replaced the reference with a brand new LM399 - first thing I did is ask them is how long they think they personally aged it, and second thing I did is... never turn it off. I think I got it back in May, and it will never be off until I decide it's ripe enough to attempt an adjustment. Of course, this treatment is tough on electrolytic caps, for one, but I'm always trying to get long service ones (>5000hrs) and also, well designed circuits will likely "encourage" wet caps to last very long.For instance, how significant (= measurable, including with meters all the way to 8 1/2 digits) a drift shall I expect from a high quality DCV standard (for instance, a 5440)? These were made in the eighties, and I assume many were probably ran continuously for extended periods of time. Mine, for instance, is probably just about 40 years old, the better part of which I assume it was mostly on in a cal lab environment.To add a bit more flesh to this topic, here's Solartron/Schlumberger's take on this, as they present it relative to their 7801 8.5 digit meter. But I'm rather looking for hands on experience on measured, or quantified drift.

author: guenthert
author_rank: Frequent Contributor
timestamp: October 21, 2023, 07:16:11 am
content: Quote from: Rax on October 21, 2023, 12:01:04 am"core voltage references"? Are you thinking of subsurface Zeners (as the ones listed)?[..]Quote from: Rax on October 21, 2023, 12:01:04 amWell, afair, the Solartron long scale DMM actually used surface Zener(s), 1N829A (or 1N825A as also used in the HP735A). I'm not so sure about Solartron's claims there. Seems more like marketing material than academic publication.Datron shared a procedure to reduce burn-in time (at that time 4 to 5years) for surface Zeners. Later products used LTZ1000 though.EDIT: it was actually V.S. Orlov who shared that procedure ("Reducing the time drift of Zener stabilization voltage") and in that text referred to data from Datron.I'd think, for best results, one doesn't rely on the stability of the device (theyalldrift, the better ones less and in a fairly predictive manner), but performs periodic comparisons.

author: Rax
author_rank: Super Contributor
timestamp: October 21, 2023, 02:25:11 pm
content: Here is a good application note, referring to the LTZ1000A:https://www.analog.com/media/en/technical-documentation/application-notes/an82f.pdf.

author: Andreas
author_rank: Super Contributor
timestamp: October 21, 2023, 02:41:44 pm
content: Hello,ageing depends on several influences.- the chip itself- the die attach- the package- influence (stress) from the PCBEach reference is individual and shows individual behaviour.From my 9 LTZ1000(A) 7 settled rather fast (within the first few kHrs)2 needed more than 1 year to go below 1 ppm/yearSo for high demands you have to measure them individually and sort out the bad ones.But this is only valid for constant environment conditions.Every night in the freezer will harm the stability for more than half a year.with best regardsAndreas

author: dietert1
author_rank: Super Contributor
timestamp: October 21, 2023, 02:44:43 pm
content: Zeners drift, yet it depends.Initial aging will be faster for standards with high temperature ovens. A typical time scale is 1000 or 2000 hours. With lower temperature ovens it will take longer, maybe 5000 hours. After that it depends on how well the standard is shielded from ambient temperature and humidity change and whether it has continuous operation with protection from power failure.There was a Fluke report about their 734A zener standards. They arrived at the conclusion that after 5 or 10 years the drift becomes predictable to a level that no longer justifies yearly calibration. Also in this forum people reported sub-ppm/year deviation from predictions, sometimes using DIY standards.Very few calibration labs operate at that level. Most of them have yet another 734A or similar. Even some national institutes run their JJA standards only once a year to check their 734A zener standards.Zeners in digital voltmeters (including 8.5 meters) that are subject to daily temperature cycles etc. will never arrive at that level and for those a yearly calibration with a better zener standard makes sense.Regards, Dieter

author: Rax
author_rank: Super Contributor
timestamp: October 21, 2023, 02:57:38 pm
content: Quote from: guenthert on October 21, 2023, 07:16:11 amThe AN82 paper states there's a logarithmic curve attached to aging of both types of references. Which would definitely not be linear (not that anyone here said "linear"). But predictive, yes - meaning from a certain point on (I'm thinking of decades), further aging may become immeasurable.

author: Andreas
author_rank: Super Contributor
timestamp: October 21, 2023, 07:15:17 pm
content: Hmm,here a example of ageing curves of 3 LM399.Price question: determine the logarithmic coefficient.Unfortunately my LM399 cannot read the paper.So they do not know how they should behave.with best regardsAndreas

author: bastl_r
author_rank: Regular Contributor
timestamp: October 21, 2023, 09:03:36 pm
content: HiThen it will probably be the LM399 with the blue curve that you get thrown at ebay...

author: Rax
author_rank: Super Contributor
timestamp: October 21, 2023, 09:46:49 pm
content: Quote from: Andreas on October 21, 2023, 07:15:17 pmThank you for this empirical data. The horizontal axis is in thousands of hours from straight off the shelf?

author: Rax
author_rank: Super Contributor
timestamp: October 21, 2023, 09:48:33 pm
content: Quote from: Andreas on October 21, 2023, 07:15:17 pmBTW, if you average those readings, they're not so far from a logarithmic curve tapering off (particularly if there's some pre-aging from factory). All three! Pretty impressive.Thank you for posting this. It's exactly the kind of stuff I was looking for - empirical data confirming this asymptotic tapering off they talked about in the paper.

author: Andreas
author_rank: Super Contributor
timestamp: October 22, 2023, 06:11:19 am
content: Hello,X-axis is in days (as stated on the bottom of the diagram).CH6+CH7 are from day zero (after some first tests).#1 running ~5 years before start of the measurement (in my lab).(earned from an old PCB with unknown history).I have also some devices which are ageing rather linear. (So asymptotic behavior probably in several 100 years).with best regardsAndreas

author: Rax
author_rank: Super Contributor
timestamp: October 22, 2023, 03:35:49 pm
content: Another paper on this, this time from TI:https://www.ti.com/lit/pdf/sbaa436The curves depicted (experimentally generated) are also logarithmic and very similar to Andreas'.

author: Rax
author_rank: Super Contributor
timestamp: October 22, 2023, 04:22:20 pm
content: Obviously, due attention should be paid to units with different scales, modes of collecting the drift, etc. Certain segments, potentially very small, or very large and "out of view/range" may account for differences between graphs.

author: Rax
author_rank: Super Contributor
timestamp: October 22, 2023, 04:43:14 pm
content: Another reference is Fluke's own paper:https://download.flukecal.com/pub/literature/6011115a-en-734C-apply-specs-an-w.pdf, where they use slightly loose language - linear and logarithmic are two different things. I wonder how much confusion that's seeding. "Linearize" likely is meant to signify a continuous plot/graph (therefore predictable?).But they also state it's in a logarithmic report with time (or sqrt).I wonder if anyone has a copy of the paper they mention (“Predicting 10 V dc Reference Standard Output Voltage” by Raymond D. Kletke).

author: Rax
author_rank: Super Contributor
timestamp: October 22, 2023, 04:45:07 pm
content: Quote from: Rax on October 22, 2023, 03:35:49 pmFor some reason, the link above doesn't seem to work as placed above, but searching for the name of the file should return it.

author: alm
author_rank: Super Contributor
timestamp: October 22, 2023, 06:49:39 pm
content: Quote from: Rax on October 22, 2023, 03:35:49 pmCareful what scale you're talking about. At the 50 uV/V scale a reference might appear to have negligible drift, but at the 1 uV/V level things are unlikely to be so smooth. Comparing it to looking at a flat surface with your eyes vs an electron microscope. Things might look pretty smooth to your eyes, but are unlikely to look smooth under an electron microscope.Quote from: Rax on October 22, 2023, 03:35:49 pmSimilar to the two out of six curves you cherry-picked, maybe.Quote from: Rax on October 22, 2023, 04:43:14 pmWhat they say is that shortly after first power on it is best modeled as a logarithmic function, but later on it best approaches a linear function. Seethis paperfor some example curves, and see figures 3 and 8 inthis paper. This aging behavior may also reset if references areturned off for a long time(long term section) orexperienced a low temperature like during shipping(AD587LW#01).It's important to realize that these Fluke 732A/B/C voltage references have been very carefully selected and constructed for a low and predictable drift. They are close to the best achievable, and even they need 4-6 calibrations against a more stable reference to establish this drift. You should expect anything else to have a larger slope and be more erratic, because there are more factors contributing to the drift. Before you have collected enough data to forecast the drift, you should assume that it's within the factory specifications (2 uV/V/year for 732C), although even that you would need to validate for an old, used instrument. For example a usedFluke 732B might drift 8 uV/V/year, far above the 2 uV/V/year specification. These references are pretty much the most carefully studied instruments, so expect anything else to have to the same problems but worse.Sometimes instruments just suddenly start drifting for no good reason. That's why you need regular inter-comparisons between independent references and calibrations against a higher level reference. A common reference for this isNIST Tech Note 430which describes how to do inter comparisons of voltage references (then Weston cells) to spot if any in the group is drifting excessively.

author: Bill158
author_rank: Regular Contributor
timestamp: October 22, 2023, 07:21:28 pm
content: Another paper from FLUKE by David Deaver on the subject of predictability of zener references. It has some interesting charts at the end about the SZA 263 from Motorola vs. the LTFLU from Linear Tech and their respective drifts.Bill

author: Rax
author_rank: Super Contributor
timestamp: October 23, 2023, 05:17:13 am
content: I still have to catch up with a good deal of quality reading material (thank you all that posted, and I regard myself and many others behind me lucky to have this resource by y'all contributions), but it looks like the provisional conclusions are:Initial plots are of course logarithmic. Sometimes, invert over Y axis, which may be shocking to those thinking we cannot read inverts...Medium term, the logarithmic curve becomes reducible to a linear plot. OK, got that.Long term (such as four decades)... Is that linear graph drawing horizontal for all intents and purposes? If "yes," (or no!) has anyone done any objective measurements? So far, all I've heard from owners of equipment this old is unabated faith in their decades old volt. Change in the volt standard some 30 years ago be darned.

author: dietert1
author_rank: Super Contributor
timestamp: October 23, 2023, 07:14:28 am
content: Most people can't afford JJA calibrations and those who can keep their secrets. You could use Flukes published drift data to estimate long term drift if you assume statistical behaviour. It will be a model though.If you want to pin down zener drift of less than 1 ppm/y or 0.5 ppm/y and the best calibration you can afford is +/- 3 ppm you need a time span of 6 to 12 years. It takes 10x that for a 10% measurement of the drift.Related discussion:https://www.eevblog.com/forum/metrology/volt-nut-meeting-2019-in-stuttgartgermany/msg2460954/#msg2460954.Regards, Dieter

author: alm
author_rank: Super Contributor
timestamp: October 23, 2023, 08:53:52 am
content: Quote from: Rax on October 23, 2023, 05:17:13 amDepends on the scale. On the 0.1% level for a 3.5 digit DMM, even your random bench supply will be rock solid over time. A very good Fluke 732A might settle down to something like 0.2 uV/V/year. The not so good one I linked to earlier 8 uV/V/year. You'll have a hard time even measuring a Fluke 731B to those levels because of the temperature coefficient. DMMs are generally worse because they have so much more components that contribute to drift. The 3458A is better because its autocal feature means uncertainty is dominated by its LTZ1000 voltage reference and the 40 kOhm reference resistor. But the LTZ1000 is ran at a high temperature so long term stability isn't so amazing (in the order of magnitude of 1 uV/V/year).What you have to do if you want to go beyond the statistical model supplied by the manufacturer is measure the drift from multiple measurements over time. And as Dieter rightly points out, it's very difficult and expensive to do those measurements with a very low uncertainty. If you measure a F732A on a standard 3458A today, and again in a year, the best you might be able to do is say the drift is less than 8 uV/V/year (the specified drift of the 3458A). To know how much less you need to either get more accurate measurements, like send the 3458A out for calibration and within 24h measure your reference, or send the reference for calibration, or measure over a longer time.

author: dietert1
author_rank: Super Contributor
timestamp: October 23, 2023, 11:09:23 pm
content: A JJA reference is so much more expensive (about US$ 400 K on NIST web site) than any zener and so much better than necessary for any real application. I think that factor 10 000 gap is the reason why we have different levels of zener references. In another world JJA references could be abundant and cheap, but our reality are those Fluke zener references.Somebody needs to invent a new kind of reference at the 0.01 ppm level and with reasonable cost.Regards, Dieter

author: alm
author_rank: Super Contributor
timestamp: October 23, 2023, 11:16:44 pm
content: Just to be clear (I know you know this, Dieter), when we talk about a higher level standard, that doesn't necessarily mean a better performing one, but rather one that is more frequently calibrated with lower uncertainties. For example there might be a golden Fluke 732 that is calibrated directly against a Josephson Voltage Standard. This 732 isn't actually gold encased and may not have a lower drift than other zener references in the same lab, but due to these frequent calibrations against a JVS, its value will be known more accurately, so it can be used to calibrate other standards with a better uncertainty than if they were calibrated against a 732 with a regular yearly call cycle and higher uncertainties.

author: Rax
author_rank: Super Contributor
timestamp: October 23, 2023, 11:22:54 pm
content: Quote from: dietert1 on October 23, 2023, 11:09:23 pmNot at all, a water-cooled 6000e is a measly $322,800!...If you factor in the "pre-delivery" calibration and other costs... such as the maintenance which may require a tech on staff to just do this baby, then, fine! Maybe it gets to $400k.

author: rhb
author_rank: Super Contributor
timestamp: October 24, 2023, 02:30:25 pm
content: Quote from: Andreas on October 21, 2023, 07:15:17 pmFWIW The aging curves are sums of exponentials which can result in reversals of trends. But asymptotically they approach zero drift. The curvature terms get very small making it almost linear after a long period.I'd love to determine the aging coefficients but both you and TiN have refused to supply digits I can use. Just graphs. Why? All I want is the opportunity to fail. It seems to me neither of you are very confident about your assertions of my incompetence and rather more worried about your status being impugned by not understanding the math.I am setting up to measure 3x LM317, 3x LM399 & 3x AD584 with my 3457A. So I *will* eventually have data despite no volt or time nut I've encountered being willing to share digits. Just graphs and arm waving.IF YOU ARE NOT WILLING TO PUBLISH YOUR RAW DATA WHAT ARE YOU HIDING BESIDES MERE IGNORANCE?Reg

author: iMo
author_rank: Super Contributor
timestamp: October 24, 2023, 03:26:24 pm
content: This is an interesting topic, indeed. It started with "core zener" and it tends towards measuring aging of such complex systems/circuits like Fluke 732ABC, LM399, AD584, etc. What are the aging contributions of those dozens parts around the core zener?I do not think somebody here is "not willing" to share "aging data".Simply it has none sense to share.The shape of the trend is perhaps known but you never know what happens next day with those complex systems. And every system is individual per-se.Unless you are able to compare your vref system periodically against other standards (like the JJA), moreover you are able to do the checks "forever", any future trend is just a guess, imho.When somebody publishes "my LTZ1000 based reference did -10ppm during the last 25years" it does not mean it will continue that way next 100 years. It could easily be it makes +15ppm next month, even the probability is low*, but it may happen.* the probability a system fails gets higher with time, afaik..

author: Grandchuck
author_rank: Super Contributor
timestamp: October 24, 2023, 04:10:15 pm
content: Quote from: iMo on October 24, 2023, 03:26:24 pmBathTub curves are often used for reliability:http://applied-statistics.org/Glossary/BathTubCurve.html

author: Rax
author_rank: Super Contributor
timestamp: October 24, 2023, 04:41:28 pm
content: Quote from: Rax on October 23, 2023, 05:17:13 amOn this last term here - which I think is of critical interest to many of us - just an observation regarding available data, studies, etc. I posit "long term" for manufacturers (Fluke, etc.) will never be in the decades scale. Years, yes, but never decades. Fluke has no interest in discovering their unsupported, no-revenue-generating ancient (but exceptional) instrument may experience immeasurable aging from, say, decade three (stay with me here for a second; and let's also ignore aging of other components, which for me - having done this kind of work for a long time now - is not a real issue). And by no interest I mean, honest, business sense, rational assessment of the fact there's no business to be had there. Anyone think they'll start supporting the 5440A/Bs etc? And if not, what pays for this research and gata harvesting etc.? All very expensive and exceptionally difficult work.And so I'll stick with my split of the curve in three above (and again, Fluke's focusing on segment #2, and has no business messing with #3). Each one needs a completely different approach, and means completely different things for different communities of users and their ecosystems. The third segment only means anything to academic research and us hobbyists here.

author: mendip_discovery
author_rank: Super Contributor
timestamp: October 24, 2023, 06:59:30 pm
content: Quote from: rhb on October 24, 2023, 02:30:25 pmIt would be nice for someone to draw up a theoretical curve and then it would be interesting to see if over time if the curve changes or if the results fall into that curve.Is it possible to make a bit bit of Python code that can look at the data an spit out a exponential graph along with the exponents.The nice kit I have access to is at work and even though I am the signatory and HoL I have a MD that wouldn't let me just have my 10V ref running in the lab and measure it with the 8.5digit meter in the lab.I do have a 1281 here at home but its sadly been abused by the previous owner, vaporized traces. Otherwise I would have that running and have the logs shared online.

author: rhb
author_rank: Super Contributor
timestamp: October 24, 2023, 11:30:32 pm
content: Quote from: iMo on October 24, 2023, 03:26:24 pmPeople who post long time series are willing to share data? Who might that be?At a minimum I'm asking for the digits used to generate the plots. Little hard to make the plots if they don't have the data. Little hard to do independent analysis from a picture.I have asked for long time series of voltage references for 10 years and have never gotten data that was usable. When I asked TiN for the metadata associated with digits he posted on his website I never got a response. No metadata, no possibility of independent analysis.If people are willing to share their data as you assert, why isn't there an ASCII file with the data used to generate the plots attached to the posts? I'd also like to note that without the supply voltage to the reference you really can't say very much.If people are willing to share their data as you assert, why isn't there an ASCII file with the data used to generate the plots attached to the posts? I'd also like to note that without the supply voltage to the reference you really can't say very much. The +/- 5% line voltage variation becomes significant at ppm levels.Furthermore I have considerable high level professional experience solving problems in the continuum mechanics of solids and fluids. How elaborate an analysis are you willing to pay for? The relevant factors are:elemental diffusionvisco-thermo-elasto-plastic deformation (the major term)crystal structure changes (arguably fundamental to diffusion process)It is certainly true that you cannot solve the problem using least squares (aka L2). However, it is equally true that *most* of the time you can get an optimal (L0) for L1 effort using linear programming. The fundamental problem is NP-Hard, but I've done weeks of numerical testing and spent 3 years learning the math. Given a year's data my tests have shown the ability to predict the change in a year to 1-2%. That's 1-2% of the *change*!I'll have 10 channels shortly (I hope) after my shielded hookup wire arrives and once I sort out using my 3497A to multiplex 100 channels to my 3457A the budget is the only limit. But I can afford to compare 40+ used LM317s to an equal number at varied, controlled and measured temperatures. Which is my initial 3497A goal for the design of a PSU which is ppm output stable to feed the references. The grid is +/- 5% so to meet the line stability requirements for an LM399 you need a very stable supply voltage that won't be affected by a sudden load event on the grid.The blue curve in Andreas' plot looks a lot like retrace from power cycling the reference. Is it or was something else going on? Those are almost certainly not the only LM399 datasets he has. Anyone can "prove" any point if they exclude data that don't agree. I thik it's called "cherry picking"?"Researchers "who won't let others see their raw data, modifications and the input to a plot are hiding something. Michael Mann et al being the extreme case of such fraud. If you conceal the data and don't permit independent analysis it's BS, not science or even engineering.Post a plot, post a CSV file to reproduce it and provide the metadata. If not, go sell used cars. You'll be good at it.Reg

author: Echo88
author_rank: Frequent Contributor
timestamp: October 25, 2023, 12:09:37 am
content: I guess nobody was comfortable sharing data due to the fact that said data is incomplete, influenced by ambient temp/humidity, changed temp/voltage setpoints during the logging or the used meter was needed for another experiment.No one on a hobby budget has a dozen different refs and annual calibrated intercomparison travel reference sitting in a climate chamber undisturbed with super clean UPS and shielded environment, logging since years to zoom into drift data , to calculate NP-hard equations that get your PP hard, but your wife mad.

author: dietert1
author_rank: Super Contributor
timestamp: October 25, 2023, 06:29:31 am
content: The idea of having a predictable zener after some years of uninterrupted running inside a temperature stable oven may be just Fluke marketing. In reality something will fail after 5 or 10 years and of course after a repair or maintainance predictability is ruined. Stupid things like a mains switch or a power line filter or the requirement to ship without batteries.Another example:When i started logging the internal temperature and humidity of our double oven ADR1399 reference after the final mods everything looked as expected: An exponential decay of internal humidity unbalance between air humidity and humidity inside a small used desiccant bag, time constant about 12 days, asymptotic humidity about 34.3 %RH. The next evaluation more or less confirmed that and i posted the plot in my ovenized meter threadhttps://www.eevblog.com/forum/metrology/prema-bk7-derived-meter/msg5059654/#msg5059654. Meanwhile humidity arrived at 32.4 %RH, so the bigger picture is linear drift. In contrast to zener drift that can't continue forever. Impossible to recalibrate the humidity sensor without destroying the log..This isn't about mathematical capabilities!I am mentioning humidity as i think the Fluke 732A oven is not monitored for humidity. Or is it filled with oil? There may be a minor chance for improvement. Andreas' blue LM399 log shows seasonal variations, so that part may be damaged with the package no longer hermetic.Regards, Dieter

author: iMo
author_rank: Super Contributor
timestamp: October 25, 2023, 07:44:42 am
content: My current understanding is the topic on the long term predictability of the zener based Vref voltage is not much related to the technicalities around it, but more less related to the fundamental laws of physics known to work in this UniverseFor example the 1/f noise - what will be the p-p amplitude of the voltage fluctuation in say 1nHz to 1uHz frequency range? The entropy of this Universe increases, that goes against the zener voltage predictability. Not talking about the BigBang and related randomness of everythingOur reference zeners work basically the same way as the old vacuum tube voltage regulators (VR tube) 100 years back. The point like random positioned centers of the light emission (the glow discharge coming off the ionization centers seen on the Noopy's great pictures of many voltage references) simply show us it is still just a random process where the ionization breakdown occurs anywhere in the material lattice. The center may relocate itself or disappear/appear almost anytime and anywhere in the active zener region based on the quantum randomness (or any external influence). That may affect the output voltage anytime, of course.Thus I doubt you can predict zener's voltage "long term", what you can do (and what the voltnuts do here) is to report the past history and show postmortem graphs, but you cannot predict the future voltage levels with great probability, imho.

author: rhb
author_rank: Super Contributor
timestamp: October 25, 2023, 01:52:39 pm
content: Quote from: Echo88 on October 25, 2023, 12:09:37 amMight be a case of not knowing how to analyze time series within the limitations of the available data.Data are *always* incomplete. But you can't do *anything* with zero data. I want to demonstrate what basis pursuit can do. But I'm forced to wait for years to collect enough data myself because it's really easy to claim I can't make the predictive models. Just withhold the data.When you are trying to suppress noise, even poor estimates can be very useful.Seismic processors routinely develop sharp, crisp images from data inexperienced people would say is just noise. How big a vibration comes back to the surface after bouncing off a layer interface 10 km below the surface? You think they wait for the ocean waves to stop?There is an old saw, "One person's "noise" is another person's data. The blue trace Andreas posted is strongly correlated with steps in the other 2 traces but the blue trace shows a slope where the others are a step. That would seem a likely result of a slow leak in a formerly sealed case in response to a step seasonal change. But without careful analysis one cannot make any conclusions. Just an observation of the correlation.Give me a 1000 series contemporaneously recorded and I can easily model and suppress correlated noise. It's harder as N gets smaller and magnitude varies between series. One does not even need to know the cause if you are trying to isolate device characteristics. If it's correlated across all series it's noise in the aging problem and only needs the magnitude for each series to remove it.If what I say were not true, the fossil fuel debate would have ended long ago. There wouldn't be oil and gas from 25,000 ft below the surface in 10,000 ft of water.Reg

author: tomato
author_rank: Regular Contributor
timestamp: October 26, 2023, 06:57:49 pm
content: Quote from: rhb on October 24, 2023, 02:30:25 pmDo you think it's possible no one helps you because of your arrogance and s%^**& attitude?Quote from: rhbQuote from: rhbQuote from: rhbQuote from: rhb

author: alm
author_rank: Super Contributor
timestamp: October 26, 2023, 08:37:50 pm
content: Quote from: rhb on October 24, 2023, 02:30:25 pmQuote from: rhb on October 24, 2023, 11:30:32 pmSo what is it? Did TiN not supply you raw data, or did he supply you raw data, but not in the format you wanted and hence wanted him to do the work to make it suitable for you? Given that raw data is available on his website I find it hard to believe he wouldn't share links with you.

author: rhb
author_rank: Super Contributor
timestamp: October 28, 2023, 03:21:03 pm
content: I asked politely for data 10 years ago. It was inconceivable at the time that people would refuse.Never got any. Tried multiple times, same attitude. You can't have any digits. So when I see data such as Andreas showed I get rather annoyed. He challenged people to extract the exponential so I asked for the data. But no data. I am not going to extract digits from a plot.Standard data analyses I've never seen posted::Autocorrelations of referencesCrosscorrelations among all referencesExtraction of environmental disturbancesTrace of mains supply voltages contemporaneous with reference dataMains supply varies by +/- 5%. For an LM399 that's +/- 20 uV which is +/-2.8 ppm. That will produce a correlated seasonal shift as the electric load varies between heating and cooling.These are the most basic steps in time series analysis. The first things you do after plotting the raw data to look for bad values.Has anyone ever posted an error budget for any reference design? I see lots of long complex lists of things that are claimed to affect the performance, but no analysis of the magnitude and in many instances there is no clear physical basis for the claimed effect. If anyone should be willing to provide data covering a thousand days please PM. Otherwise I'll be back next year when I have my own data from 9 references and the PS measured with a 3457A & 44492A.Reg

author: Echo88
author_rank: Frequent Contributor
timestamp: October 28, 2023, 06:05:08 pm
content: References are usually powered by a regulator with a specified PSRR that'll make any mains voltage variation irrelevant, if you dont put the varying heat producing transformer/regulator in close vicinity to the ref and thereby changing its ambient temp.

author: rhb
author_rank: Super Contributor
timestamp: November 02, 2023, 11:14:39 pm
content: PSSR? Power Supply Ripple Rejection?How will that correct a 10% variation in mains voltage? It's not ripple and is not predictable.Very dependent on grid load.Please crunch through the error analysis for the reference of your choice using simply supply variation and load variation from the datasheet. based on +/-5% mains variation.Reg

author: Echo88
author_rank: Frequent Contributor
timestamp: November 02, 2023, 11:30:27 pm
content: 230V +-10% -> transformer with say Usec 15V -> rectifier -> regulator with high PSRR -> stable and smooth Udc for the ref of your choice, where 10% mains variation is irrelevant with enough regulator headroom.https://www.analog.com/en/design-center/glossary/psrr.htmlPlease crunch through the basic math of designing a regulator.

author: rhb
author_rank: Super Contributor
timestamp: November 03, 2023, 12:04:03 am
content: Quote from: tomato on October 26, 2023, 06:57:49 pmMy attitude is the result of 10 years of asking for digits and not getting them. I'm waiting for shielded wire to measure 9 references and the supply using a 3457A/44492A. When I sort out using a 3497A to multiplex 100 channels I'll increase that.The problem with people who never learned mathematics is they never learned to analyze data.Why should anyone believe the conclusions of someone who doesn't know how to properly analyze multichannel data?Andreas posted plots challenging anyone to derive the exponentials. I can, but I've never received any data. He has done similar things every time he posts graphs.Tune in next year for the fun and games.RegQuote from: Echo88 on November 02, 2023, 11:30:27 pmBTW It's +/- 5%. Please learn to read with better comprehension. What regulator do you claim performs these miracles of long term stability? How do they know that the line voltage is 3 V higher or lower than 6 months ago. And what the hell is Usec and Udc?My results using LM317s for the Vdc showed I need at least 2 in series per the datasheet to properly feed an LM399.And reference measurements that don't include the supply voltage are damn poor work.In any case, anyone claiming to be a scientist who will not provide their raw data is a fraud. And a con man if they alter the data without disclosing what they did a la Michael Mann and friends "climate corrections" engineered to support a fraud to gain public funding.BS is BS and should be identified and treated as such.Reg

author: dietert1
author_rank: Super Contributor
timestamp: November 03, 2023, 07:17:30 am
content: You could search the forum for "exponential decay" and get many hits, among themhttps://www.eevblog.com/forum/metrology/the-ltflu-(aka-sza263)-reference-zener-diode-circuit/msg3574213/#msg3574213.This forum isn't so much about mathematics but about electronics.By the way, those LTFLU references later became a low linear drift case. One can picture this like nuclear waste decay. There is a mixture of multiple exponentials with largely different lifetimes. And the process is statistical, so reference drift isn't continuous but exhibits "bubbles". Intermediate periods of 500 or 700 hours without any drift were observed.Others less optimistic don't expect exponential decay but random walk proportial to square root of time, so ever decreasing drift rate without asymtotic value.Regards, Dieter

author: dietert1
author_rank: Super Contributor
timestamp: November 03, 2023, 10:29:01 am
content: If one suspects long term aging of a reference is linear drift, it might be caused by cosmic rays. I found this paper:https://www.researchgate.net/publication/338671492_Optimization_of_shielding_to_reduce_cosmic_radiation_damage_to_packaged_semiconductors_during_air_transport_using_Monte_Carlo_simulationSeems one needs more shield thickness than a hammond aluminum enclosure.Regards, Dieter

author: ramon
author_rank: Regular Contributor
timestamp: November 03, 2023, 04:18:11 pm
content: Rax,'The user should consider leaving the voltmeter switched on and avoid extreme environmental conditions'I really loved to have the DMM running tests for several weeks uninterrupted, but I decided to stop the device 24x7 for two reasons:1) I have no way to provide stable temperature/humidity enviroment. Any data is useless without this.2) now I am more risk averse and cannot leave the DMM unnatended (fire safety paranoia).I found that many many other things are really important: DMM AC line input voltage fluctuations, or DC voltage reference input changes, vibrations, RF/EMI, any person walking nearby the room, etc ... Surprisingly, I was not able to detect meaningful variations during one earthquake (but only experienced one while collecting data).rhb, I would be very happy to provide a 'real-time RAW data feed' if someone provides the money to run the DMM on a datacenter/colocation site with stable temperature AND the contract has written that they allow me to install weird things like a 20 years old DMM with DIY voltage reference AND will NOT sue me if the R6851 or V reference starts fire and gets the whole building down, AND that there is full insurance for the datacenter AND any third party, ... even if someone dies two years after the fire ... AND over all and everything. (Wow, I am so exaggerated! or not)So datacenter/Colo will have to reserve 1U/2U for high quality Online UPS, 3U for DMM/Voltage Reference/linear power supply, and 1U for server to get data and provide feed. So around 6U. If RF/EMI control is required then need around 9U space for isolation/case. Add to this the monthly ISP costs for providing RAW DATA. And don't forget Insurance. What do you say? Deal or not?

author: ramon
author_rank: Regular Contributor
timestamp: November 03, 2023, 04:30:40 pm
content: (TOTALLY OT) This reminds me when I was investigating the cost of real-time data feed of exchange rate and stock market. There are only two companies that provide it (Bloomberg and Thomson Reuters). Had to pay something like 3K or 15K per month. And they didn't provided the 'real-time' raw data, they provided data with +15 minutes delay. I don't remember if they provide the RAW data directly, or just only a terminal in which you can see the data. Was really interesting topic. And found that there were some sites providing the data for free (with some addeduncertainty.

author: Echo88
author_rank: Frequent Contributor
timestamp: November 03, 2023, 06:46:12 pm
content: For someone named Reg you should now your regulator stuff better.Us math-deficient people who arent into geology and mathematics simply use superior contemporary regulators like the LT3042 instead of 60 year old series connected LM317.I could calculate the mains deviation to LDO-output attenuation on a napkin or your geology diploma, but ill guess you can do that yourself. After all you had 10 years time to learn that stuff.Attached is a simple transformer fed LT3042 simulation, so you can play around with your mains tolerance.Anxious about long term regulator drift? Attach a Vref as on page 25 of the datasheet or do a closed loop compensation.Always happy to help if you have other questions that you want answered.Gotta go now, Michael Mann invited us to a poker round.

author: iMo
author_rank: Super Contributor
timestamp: November 04, 2023, 08:35:56 am
content: OT - the LT3042 is low noise but not "particularly stable" as its output voltage depends on the TC and long term stability of the external resistor (the resistor hidden inside the C1 capacitor's params in your schematics).

author: Andreas
author_rank: Super Contributor
timestamp: November 04, 2023, 10:18:40 am
content: Hmm,so let it drift by 0,1V (~1%) over time.My LTZ references typically have 0.06 ppm/V so this would change the reference output voltage by 6 ppb or 42 nV.with best regardsAndreas

author: Echo88
author_rank: Frequent Contributor
timestamp: November 04, 2023, 01:47:37 pm
content: Yes, TC/ long term stability depends on Rset TC/stability, also guarding is advised as mentioned in the LT3042 datasheet.I mentioned the page 25 adding of an external ref, so you can make it exceptionally stable and low noise.Its own PSRR and the added PSRR and long term stability of a good self-fed LM399-circuit (page 6 of the datasheet for example) will however make short work of any small Vreg drift, like Andreas stated.

author: TUMEMBER
author_rank: Regular Contributor
timestamp: November 04, 2023, 02:56:09 pm
content: Quote from: dietert1 on November 03, 2023, 10:29:01 amPerhaps it is the influence of cosmic radiation, but I would rather point to more trivial environmental influences. Humidity changes periodically more often and it has a much greater impact on "large areas" of PCBs, capacitors, resistors and all that crap on the boards.This is an example of how much the change in humidity "detunes" industrial standards. What is not in a "metal cap" or at least ceramic is only suitable for a car.https://www.edn.com/factors-affecting-reference-long-term-drift-performance/You need to have a lot of determination to properly obtain and analyze a large amount of data and properly estimate it as to the causes of the disorder.Może to wam się przydaMaybe this will come in handyhttps://www.evidentlyai.com/blog/data-and-prediction-drifthttps://docs.evidentlyai.com/reference/data-drift-algorithm

author: rhb
author_rank: Super Contributor
timestamp: November 04, 2023, 03:06:12 pm
content: There is no need for a real time feed. Just data correctly labeled over a long period. With multi-channel data one can make pretty good approximation of the relative temperature coefficients even without temperature control or measurements.I think I've sorted how to modify a 3497A to multiplex 100 channels into my 3457A. And eventually 3458A if I successfully repair the one I bought yesterday. Which leaves the question of how many Vrefs I'm willing to buy.My interest is determining the aging curve as a means of correcting known systemic errors over time. I got reinterested in Vrefs and Vregs when I did the error budget for the CTI OSCA5B02 OXCOs and realized that the +/-5% mains variation was a very large source of long term random errors which are distinctly non-Gaussian and an order of magnitude larger than my .01 ppb/yr goal. Single OXCOs will hold .1 ppb for days, so my goal is to use intercomparisons and historical data to adjust the control voltages.@Andreas lets take the realistic case of the input voltage to the Vref varying by +/- 5% that's 0.5-1.0 V for an unregulated DC supply. So do you have an autotransformer? If so measure the output of your Vref supply as you vary the input mains voltage. How stiff is it? And how did you achieve that?RegThanks for the EDN link.

author: iMo
author_rank: Super Contributor
timestamp: November 04, 2023, 04:06:50 pm
content: Nobody is using a Vref (meaning the reference board with the chip or the chip itself) directly wired to an unregulated supply hanging on the mains, nobody..Quote from: rhb on November 04, 2023, 03:06:12 pm

author: ramon
author_rank: Regular Contributor
timestamp: November 04, 2023, 04:31:23 pm
content: I agree that real time is not needed and for long term temperature control might not be needed, but measurement should be needed to stablish any correlation. Congratulations for your 3458A purchase, you will not need anyone. Good Luck!My 2 cents, start first with 8*1.5V(AA). For mains powered It took me one full month of testing and modifications to reach to +/-1ppm level.During the journey, I discovered a faulty PSU and the importance of ferrite cores. Luckily many others posted pretty good information (Thanks Andreas for helping even if you didn't even know it).If you want to know current aging of this reference, you can ask TIN (but don't know if he still keeps it or not). It had a cute case.

author: dietert1
author_rank: Super Contributor
timestamp: November 04, 2023, 05:10:17 pm
content: Quote from: TUMEMBER on November 04, 2023, 02:56:09 pmI remember that EDN article and it's a valid contribution, yet a bit confusing. In Fig. 10 they show the important effect of humidity on plastic packages, but that has little to do with long term aging. Their logs indicate that the devices rapidly return to previous state once the condition is removed.In my understanding long term aging is about processes that can't be undone. Humidity aging would be something like "rust" formed in the presence of water. This would be starting on a semiconductor surface.Long term aging by years of day/night temperature cycles is another example.Also when i see those chip images of noopy with the zeners emitting light, i remember the degradation of LEDs and their limited lifetime. Also i am asking myself how light emitted by a buried zener is visible from the outside. This time aging would happen inside the semiconductor.Rare cosmic shower events will also contribute aging inside semiconductors. Making a radiation protection shield seems to be something simple one could try in a hobby lab, e.g. making covers for existing reference builds that are already well protected from ambient temperature, humidity and air pressure variations and from EMI.Regards, Dieter

author: iMo
author_rank: Super Contributor
timestamp: November 04, 2023, 05:40:17 pm
content: The Sodium (Na) is a semiconductor devices killer, for example. I remember an article on the early days of microelectronics industry in Japan, where they fought against the table salt in a new fab building built close to the sea shore. They made CMOS chips and their chips degraded pretty fast. They had to install special filters such the air vapors did not contain the NaCl (common salt). All chips are covered by a passivation layer (silicon nitride or/and silicon dioxide glass) and even with that layer the vapors containing salt may diffuse inside and affect the charges distribution.

author: rhb
author_rank: Super Contributor
timestamp: November 05, 2023, 12:55:01 pm
content: Quote from: iMo on November 04, 2023, 04:06:50 pmI should certainly hope not. My point is *measure* what effect that change has on the output voltages of the PS and Vref. I plan to test several lab PSUs later today using a pair of 34401As and a 3478A to measure the AC input and 3 LM399s. AC in, DC out of PSUs and LM399s.Reg

author: alm
author_rank: Super Contributor
timestamp: November 05, 2023, 09:33:34 pm
content: Quote from: rhb on November 05, 2023, 12:55:01 pmIn a well built reference circuit, like the "portable calibrator" application circuit from the Linear LM399 datasheet, the zener is fed from the output voltage, so even without any upstream voltage regulator the voltage coefficient is greatly attenuated. The same applies to LTZ1000, LTFLU etc circuits. Here is an example of a sweep of an LTZ1000-based reference over an input voltage range from 10.20 V to 20.20 V without any voltage regulator beyond the LTZ itself. The effect of this huge change in input voltage is just 0.85 uV/Vout (0.09 uV/Vout/Vdc):Seehere for raw data.

author: macaba
author_rank: Regular Contributor
timestamp: November 06, 2023, 09:48:40 am
content: ADR1399 output voltage deviation vs. heater voltage, attached. Feeding with LDO is probably sensible here.

author: iMo
author_rank: Super Contributor
timestamp: November 06, 2023, 10:04:52 am
content: FYI - my early experiments with the ADR1001 preprod sample showed -0.75ppm/Volt at the 10V output..

author: rhb
author_rank: Super Contributor
timestamp: November 06, 2023, 01:15:21 pm
content: I tested a couple of linear supplies yesterday. Unfortunately I was not able to get any usable data because of EMI most likely from the DSO SMPS, but will try again with my Tek 485. However, despite the noise the PSUs appeared to be much better than expected. I did observe >100 mV variation in the autotransformer voltage between readings which I need to investigate.Setup was autotransformer feeding the PSUs and a 3478A and the PSU feeding a 34401A. I had planned to then feed the PSU to an LM399, but concluded I will need to mitigate the EMI first.I'm currently setting up a larger lab space, loading up a 6 bay, 6 ft tall rack and trying to sort out where to put the instruments. So it'll be some time before I can setup a proper repeat.Reg

author: EC8010
author_rank: Frequent Contributor
timestamp: November 06, 2023, 05:25:21 pm
content: Quote from: dietert1 on November 04, 2023, 05:10:17 pmI'm afraid not. Well, not unless you consider a >4" thickness of lead all round to be something simple and easily done. That means you're looking at a 9" cube of lead to encapsulate a 1" cube containing voltage reference. Oh, and a quick calculation says the lead will weigh >90kg. Lead castles areheavy. Cosmics have a lot of energy and are not easily stopped. It's why radiation measurements needing really low background are done in salt mines.rhb: Lead-acid batteries are your friend. I have a pair of 12V 2.2Ah lead-acid batteries in a screened tin with their outputs on BNCs. That way, I can test stuff and discount mains EMI.

author: rhb
author_rank: Super Contributor
timestamp: November 07, 2023, 01:10:22 am
content: If only EMI were so simple. How do you propose to maintain a constant voltage from lead acid batteries over years?So far as I can see, for multi-year experiments the only option is a *very* stiff regulator fed from a UPS with heavy filtering of the UPS output and likely shielding the UPS enclosure.On my current bench all the power from the Topaz 2.5 kVA isolation transformer is in conduit all the way to the IEC sockets to suppress picking up radiated emissions. The new lab will have a similar installation, but with EMI filters in every junction box, one per instrument. I'm also going to make lots of shielded test leads with the shields grounded at one end only to prevent ground loops.Much to my surprise and dismay I seem to be one of very few people on the forum who understand multi-channel time series analysis at the level of 'Random Data" by Bendat & Piersol or all the tricks DSP will let you do if you have a large amount of data (i.e. millions of samples for each of a large number of channels.I am modifying a 3497A to multiplex 100 channels to a single DMM. A 3457A to start and a 3458A once I repair the one I just bought. When that will happen is unknown. My primary interest is RF and my volt-nutting is driven by the demands of the OXCOs I am going to test. This is all just for fun, so I reserve the right to switch projects at my discretion. I also do metal and woodwork, play guitar and many other projects. About all they have in common is being very difficult. I'll leave easy to other people most of the time.I spent several years solving continuum mechanics of materials problems and writing software for that. I am very dubious of many claims about Vrefs, for example that stress on the leads causes voltage shifts. I find it very hard to believe that stress on the PCB connections can be transmitted by the leads to a die with sufficient force to have a noticeable effect. I may well be wrong, but I intend to *measure* it by deliberately deforming the leads. Main goal is to predict aging accurately enough that aging drift can be quantified and corrected.A related project is OXCO aging which requires voltage stability at uV levels. I think most people in the Metrology section grasp that maintaining 1 uV stability borders on impossible. I bought 110 used LM317s which I shall test over the course of a year and select the ones with the best tempco and load and supply stability.Those will be used probably in sets of 3 to provide Vc to the Vrefs.Have Fun!Reg

author: iMo
author_rank: Super Contributor
timestamp: November 07, 2023, 08:12:00 am
content: Do not waste your valuable time with measurements which are, at first glance, vain. There is a certain knowledge base the voltnuts here gathered within many years of their experiments. It seems to me you somehow ignore the messages here on what is feasible and what is not.If you wrote you want to measure/observe (for several years) 110 pieces of, for example, ADR1000s or similar gadgets, that would be something pretty interesting to talk about.The LM317 has nothing to do with any precision or stability at ppm levels, it is a cheap jelly bean voltage regulator.As the first thing people would recommend to you is to repair and adjust your newly acquired HP3458A. That may take significant effort and time and people here will certainly advice you in that pretty tough exercise, imho..

author: dietert1
author_rank: Super Contributor
timestamp: November 07, 2023, 10:46:23 am
content: EC8010, as far as i understand most of the high energy particles cause showers in the atmosphere, so at ground level we can expect large amounts of lower energy particles. In the paper i linked they were considering protons and neutrons as causing semiconductor damage and the absorption curves show that one doesn't need to use lead. In fact their final proposal was a combination of steel and borated PE. Even water in jerrycans could work.But yes, as simple as building a cover is, it may be cumbersome due to the amounts of material involved.I was bringing up those ideas after getting suspicious that some voltnuts may just have been lucky with their setups. For example two LTFLU references i made are inside aluminum enclosures with about 5 mm wall thickness. In order to get good thermal contact for TEC temperature control i used old transformers on top as weights (maybe 10 cm of iron). Others use cellar labs. A desk setup close to a window with little extra cover may be a disadvantage - also for aging of the person..Regards, Dieter

author: iMo
author_rank: Super Contributor
timestamp: November 07, 2023, 11:03:32 am
content: This guy built pretty nice cloud chambers, imho, and shot a lot videos on it.I saw similar in-situ at DESY in Hamburg 30y back, was a great experience to see all that particles flying around.

author: rhb
author_rank: Super Contributor
timestamp: November 07, 2023, 01:49:32 pm
content: Quote from: iMo on November 07, 2023, 08:12:00 amIt's still a Vref and follows the same physics. And they are cheap.More importantly, I am *not* seeking a voltage reference. I am trying to build a 10 MHz reference oscillator stable to 0.01 ppb/yr by using DSP to correct the drift using a set of 4 OXCOs. I need a very quiet and stable PSU to do that.I plan to compare sets of 40 new and 40 used LM317s in an oven with the remaining channels being used to sense temperature at multiple points. I chose them because they are cheap and I need a lot of data to develop a mathematical aging model. I also need to test my 3497A hack. After the LM317s I intend to repeat with 10 new and 10 used LM399s. Possibly more, though I don't want to spend $1000 or more to fully populate all the 3497A channels. But I will compare some newer references during the LM399 run.My observation looking at graphs of aging is that it is of the basic form V(t) = A*(1-exp(-b(t))). The limit as t gets large is A. I want to study the form of b(t), the exponent. The dominant aging mechanism is clearly thermo-viscous. I think I have enough experience to characterize properly given enough data. Strictly speaking V(t) is a sum of multiple exponentials. But this is an awkward place to write such equations.The 3458A is pretty low priority. Main priority is to bring up my extensive suite of RF instruments, e.g. my 8510C 10 MHz - 20 GHz VNA cost over 3x the 3458A ($2400 delivered). I've built one rack 6 bays long and 6' high, but it appears I'll need to build a 2nd one to get all the CRTs at a comfortable level. This is a *very* large suite of RF T&M kit.Have Fun!Reg

author: tomato
author_rank: Regular Contributor
timestamp: November 07, 2023, 03:49:59 pm
content: Quote from: iMo on November 07, 2023, 08:12:00 amThis seems to be a case where someone is so determined to apply his favorite tool to a problem, that no amount of experience or advice is going to deter him from proceeding down that path.

author: Echo88
author_rank: Frequent Contributor
timestamp: November 07, 2023, 06:14:30 pm
content: First its using selected LM317 als regulators in series to power refs.Suddenly thats not the case and you want to use them to determine an aging behavior model.Its difficult to follow the plot.

author: branadic
author_rank: Super Contributor
timestamp: November 07, 2023, 06:28:46 pm
content: Here are my 2 Cents on that topic. My ADR1000 referencehttps://www.eevblog.com/forum/metrology/lowest-drift-lowest-noise-voltage-reference/msg5109708/#msg5109708,which was temperature-compensated to a very low level, used to fit an exponential drift behavior at the very beginning (see attachement), but stopped to fit it at some point. So I gave up on trying to fit it to some known equation by now.branadic-

author: rhb
author_rank: Super Contributor
timestamp: November 08, 2023, 12:14:35 am
content: Quote from: branadic on November 07, 2023, 06:28:46 pmFinding the correct equation is the crux of the problem. But 3 months of data is too short a series.I did very good fits to the increase in pore pressure with depth with 150 GB of data using polynomial exponents. That is NOT something MATLAB is going to magically find. I did that work using the superb Marquardt-Levenberg routine in gnuplot. There are multiple phenomena that affect the pressure so it's not a single variable problem and the arithmetic is very sensitive to numerical roundoff. You have to guess a coefficient which is close enough to not blow up least squares.I start with solving for a constant exponential and then add terms to b(t) which are powers of t. That takes a day or so to get what I consider an acceptable fit for any particular curve. I did the same with all the thermobathymetry data NOAA had in the GoM. The Excel users were quite amazed at my fits. But all they did was solve the wrong problem as in the preceding MATLAB example.I find it amusing that EEs can't solve math problems that someone with a BA in English lit can. Though in fairness, I probably racked up almost 40 semester hours of advanced math after getting my BA.All these voices claim I'm wrong, stupid, crazy or some combination. But WON'T supply data that would let me prove whether I'm right or wrong. Seems to me as if THEY are afraid I might succeed and in doing so impugn their "expertise".The only reason I replied to this thread was @Andeas' challenge to fit exponential curves to the 3 LM399 units he posted in a graph. Unfortunately, I can't do that from illegibly annotated plots. I need ASCII data, the input to the plot. But no one has ever supplied the data they graphed.I thought that perhaps @Andeas would provide data for a response to his challenge in post #6 in this thread. But no, same old BS. "I can't do this and neither can you. But just to be safe, I'm not going to give you ANY chance of proving you can do it. That might make me look bad."Seems to me that puts you in the Michael Mann et al crowd, modify the data, analyze the modified data, refuse to allow anyone access to the raw data, your "corrections" or the modeling software source code. They don't want anyone to be able to show they are frauds.Science depends on independent replication. History is left to tell the truth. A pile of LM317s are quite adequate to demonstrate the aging effects of buried zeners. It does not require ppm level accuracy.My need for a ppm stable supply for the OXCOs motivated buying the used LM317s. They are likely far enough along the exponential that the drift is very nearly linear which in some ways makes it harder and in some ways makes it easier.Reg

author: alm
author_rank: Super Contributor
timestamp: November 08, 2023, 12:23:56 am
content: Quote from: rhb on November 08, 2023, 12:14:35 amCharming as always.Quote from: rhb on November 08, 2023, 12:14:35 amDoesn't the LM317 use a bandgap reference rather than a buried zener? Is the physics for polishing a surface down to the mm the same as the physics of polishing a surface down to the nm?

author: rhb
author_rank: Super Contributor
timestamp: November 08, 2023, 02:39:43 am
content: The LM317 datasheet shows a zener in the functional diagram. I can find no mention of band gap in the datasheet. In any case, it's pretty much irrelevant.The first order aging term is the thermo-viscous response of the wirebonds. The rapid cooling of the wirebond results in a strain in the wirebond which affects its area and hence resistance. This relaxes more quickly if one anneals it by operation. In the mechanics of materials world this is pretty routine. Eventually ion diffusion and other lower order terms become predominate. At which point the zener vs band gap *might* have some relevance.All I have ever asked for was ASCII data I could analyze. There are 3 possible outcomes:I'm proven a blowhardI'm wrongI'm rightThere are people here with years of data which I can only replicate in an equal amount of time and considerable effort. My forte is data analysis. I posted asking if anyone had experience with multi-channel time series analysis. The responses indicate that very few if anyone does. Rather like being framing carpenters, but not knowing enough trig to calculate the length of a rafter. To me very strange.If anyone is willing to share data PM me, but otherwise I'm gone.Reg

author: tomato
author_rank: Regular Contributor
timestamp: November 08, 2023, 02:51:07 am
content: Quote from: rhb on November 08, 2023, 02:39:43 amYou stated you asked for data ten years ago. That begs the question, why didn't you just collect your own data sometime during the past ten years?

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: November 08, 2023, 02:53:19 am
content: Quote from: dietert1 on November 04, 2023, 05:10:17 pmBob Pease commented on cosmic rays in a few articles e.g.https://www.electronicdesign.com/technologies/test-measurement/article/21773611/whats-all-this-teflon-stuff-anyhowAlso, where I live, there is a natural background radiation of about 0.14 uSv per hour. If a building is made from certainmaterials, the level inside the building can be higher.I hadn't though of it before, but for enclosures of ultra-sensitive electronics, it may be worth checking the enclosure's radiationscreening with a radiation detector.I have a small portable meter and a radiation source (Uraninite ore), which I bought from Amazon during the Fukushima debacle,to check items from Japan.

author: dietert1
author_rank: Super Contributor
timestamp: November 08, 2023, 08:00:15 am
content: Thanks for the link, an interesting read. As the usual 6.2 V precision zener runs in avalanche mode, the number of electrons probably multiplies by some factor. Certainly the electrons will cause extra zener noise. Don't know to which degree they also cause crystal damage. Certainly KeV or MeV protons or neutrons can cause permanent damage.A lab radiation source may serve for a counter test - somewhat faster than shielding the setup and waiting for less aging.Regards, Dieter

author: iMo
author_rank: Super Contributor
timestamp: November 08, 2023, 09:07:07 am
content: Quote from: alm on November 08, 2023, 12:23:56 amLM317 is bandgap (1.25V). None burried zener inside..

author: TUMEMBER
author_rank: Regular Contributor
timestamp: November 08, 2023, 01:39:41 pm
content: Don't play with uranium. If such high radiation intensity surrounded your patterns, this problem would no longer concern you. Leukemia would simply kill you faster if you saw a measurable effect. In fact, the dominant effect you may be dealing with at "sea level" is the impact of increased Radon levels. Alpha radiation (protons) do not pass through the "metal caps" of LM399 or LTZ 1000. Neutrons pass through 10 cm of Pb without any problems and no one floods the references in the lead block. Cosmic radiation is only a small part of what we get from the Earth's background. Radium, Uranus , Thor are the main emitters of Radon.https://www.infineon.com/dgdl/Infineon-MOSFET_CoolMOS_CFD7A_Cosmic_Radiation_Assessment-ApplicationNotes-v01_00-EN.pdf?fileId=5546d4627a0b0c7b017a1415c2ef1185&da=thttps://www.renesas.com/us/en/document/whp/using-voltage-references-precision-signal-paths-space-applicationsLong and wise, hard to digest.https://ntrs.nasa.gov/api/citations/20180001142/downloads/20180001142.pdf

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: November 09, 2023, 12:47:26 am
content: Quote from: TUMEMBER on November 08, 2023, 01:39:41 pmI had an interesting experience buying the Uraninite ore sample from Amazon. According to the listing it was safe to ship via USPS:QuoteOn arrival here, Australian Customs questioned it. I pointed them to the Amazon listing, and Customs let it through.Testing the sample now, located in its closed metal container: detector sitting on the container: 0.7 uSv/hr (5 x background);With one mild steel sheet (coffee can lid) in between closed container and detector: 0.5 uSv/hrWith two mild steel sheets: 0.5 uSv/hr (same as one sheet)So it looks like the mild steel blocks some emission types (alpha particles?), but not all (gamma radiation?).https://www.radetco.com/your-complete-guide-materials-that-block-radiation/

author: iMo
author_rank: Super Contributor
timestamp: November 09, 2023, 06:37:20 am
content: 5x background is nothing. An old WWII wrist watch creates even more today.Alpha and beta do not penetrate your steel boxes. It is gamma only. For alpha (most dangerous for us when alpha source ingested, otherwise alpha is not penetrating our skin) you would need a special detector, not so common. The common GM tubes do not detect alpha/beta. A common GM tube detects secondary electrons ripped off its metal/glass tubing by a flying through gamma ray.

author: TUMEMBER
author_rank: Regular Contributor
timestamp: November 09, 2023, 01:21:34 pm
content: Quote from: iMo on November 09, 2023, 06:37:20 amAnd here is the problem. Solid uranite particles "have to be licked" to get into the body. Radon is a gas and you don't have to try hard to get it into your lungs. Just breathe. While uranium glass can be kept for decoration in a room where you spend your daily stay, I would not want to keep an additional Radon emitter in such a room.I liked the video you posted because it shows how intensely Radon gas works and how massive and dense its impact is.

author: iMo
author_rank: Super Contributor
timestamp: November 09, 2023, 01:59:13 pm
content: Thus every voltnut has to get an ion chamber. I already collected some mosfets and cleaned up a tin can from baked beans with tomato sauceIt can detect all possible particles including alpha, and it is easy to build.. Best to put the voltage reference inside the chamber, you will get the actual radon doses and ref voltage fluctuations cased by radiation perfectly in sync..