the issue of resistor drifts is mainly related to the amplifier (7 to 10V) gain resistors, the other resistor drifts do have a very limited impact on the output (see data sheet).
> Gesendet: Freitag, 03. Juni 2016 um 23:47 Uhr > Von: "Lars Walenius" <lars.walen...@hotmail.com> > An: "volt-nuts@febo.com" <volt-nuts@febo.com> > Betreff: Re: [volt-nuts] LTZ1000 project build > > > My experience is that boxes makes the time constants for humidity longer but > does not take it away. Heating in boxes takes the change due to humidity down > a little but it doesn´t go away. I have had boxes with LM399 and amps for > 7-10v with wirewounds for more than 20 years and they have definitely had > seasonal variations. Also if you have a completely sealed box with varying > temperatures the relative humidity in the box changes if the humidity is not > close to zero. > > A 10V 2ppm ref on Ebay was said to have no humidity effect but my unit > definitely varied about 20ppm due to humidity during a long humidity test. > One guess I have is that some units have much longer time constants due to > better sealing but I am quite sure it doesn´t go away complete. Another > problem with humidity I have seen is that you may be cheated by humidity > changing over the season and cancelling the aging. This happened during my > first tests of AD587KRZ many years ago. During the first four months two > samples both had less than 2ppm drift and the humidity in the room changed > from 45 to 25%RH so they looked very promising. But during the next four > months when the humidity went up they drifted 15ppm. > > Probably the 5 and 2ppm/C versions is manufactured in the same way. The > humidity graph under severe humidity and temperature testing shows a 500pm > difference for your chosen resistors. So doesn´t say so much. Hopefully they > are below 1ppm/%RH with low loads. > > Lars > > Från: Ian Johnston<mailto:i...@ianjohnston.com> > Skickat: den 3 juni 2016 20:42 > Till: volt-nuts@febo.com<mailto:volt-nuts@febo.com> > Ämne: Re: [volt-nuts] LTZ1000 project build > > Hi, > > The product I designed to use the 2ppm/degC resistors is sealed in an > enclosure where the LM399AH etc live, so I don't expect much problem > with humidity. > > I use 2K2, 3.3K, 10K & 22K. > > It's the RG2012L series from Susumu:- > > http://datasheet.octopart.com/RG2012L-103-L-T05-Susumu-datasheet-13139546.pdf > http://www.susumu.co.jp/common/pdf/n_catalog_partition01_en.pdf > > The 2nd PDF above is mainly for the 5ppm versions but does contains > various graphs including humidity. > > Ian. > > > > On 03/06/2016 17:01, Lars Walenius wrote: > > Hi, > > > > Do you have any idea of the aging and humidity sensitivity of these 2ppm/C > > resistors? > > > > I have tested many resistors during the years and my opinion is that tempco > > is not the biggest problem for normal nuts use but of course may be if you > > sell a product. For a nut it is quite easy to check the tempco but not > > aging and humidity sensitivity. > > > > Of the resistors I have tested it is only hermetical sealed resistors that > > I don´t see a humidity sensitivity on. Even if they are bulk metal foil, > > wire wounds or metal films with low tempco´s they seem to have very varying > > humidity sensitivity if not sealed. Lower values of resistance (100-1k) > > normally seems to be better than 10-100kohm values that in all families may > > have up to 1-2ppm/%RH. > > Last year I bought wire wounds, to be used in a LTZ1000 based design, that > > were supposed to be insensitive to humidity but they were not. They were > > even worse than other brands of WW and had several months of time constant. > > After a while the manufacturer admitted that it was a problem in the > > manufacturing and they were humidity sensitive. So far I haven´t received a > > replacement. > > > > Of course if you have a resistor with 2ppm/%RH and a seasonal variation of > > 50%RH it is only maximum 1ppm seasonal variation on the output on the LTZ. > > That is not easy to measure for most of us nuts. > > > > Lars > > > > Från: i...@ianjohnston.com<mailto:i...@ianjohnston.com> > > Skickat: den 26 maj 2016 13:35 > > Till: il...@xdevs.com<mailto:il...@xdevs.com>; > > volt-nuts@febo.com<mailto:volt-nuts@febo.com> > > Ämne: Re: [volt-nuts] LTZ1000 project build > > > > Hi all, > > > > TiN, out of interest I spent ages fishing for low ppm/degC resistors for my > > own reference......ended up with 2ppm units from DigiKey. Yes, they are > > expensive and send the BOM into the clouds!..............so I know how you > > feel! > > > > Ian. > > > > > > ----- Original Message ----- > > From: Illya Tsemenko [mailto:il...@xdevs.com] > > To: volt-nuts@febo.com > > Sent: Thu, 26 May 2016 18:42:54 +0800 > > Subject: [volt-nuts] LTZ1000 project build > > > > I'm glad my little project got so much attention. Worth to mention few > > points regarding my (or any other LTZ1000) unit: > > > > A. One should consider cost of whole BOM, not only LTZ chip. In my case > > resistors from VPG exceed cost of LTZ1000 by far. > > B. PCB I designed was targeted best to my own application need, where > > compact size and direct output (whatever is coming out of LTZ) were key > > importance. Since modules are part of bigger system with DAC synth, > > specific value, like 7.1500000 was not important for me. > > C. If there is large enough group to have this project going, I can > > actually modify original design (e.g. for easier hand soldering, or > > added buffer or ratio circuits, onboard LDO, you name it) and get PCBs > > made for interested nuts, at small cost. > > > > You can also find lot of temco/stability data with > > temperature/environment logs with mentioned LTZ modules on my site here: > > https://xdevs.com/services/ in LTZ1000 voltage reference tests section. > > RAW DSV data are available. I still have 3 modules at hand for any > > testing/checks (one was sold while ago, one was installed in HP 3245A > > source to replace LM399). > > > > Illya "TiN" Tsemenko > > > > _______________________________________________ > > volt-nuts mailing list -- volt-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > > and follow the instructions there. > > _______________________________________________ > > volt-nuts mailing list -- volt-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > > and follow the instructions there. > > _______________________________________________ > > volt-nuts mailing list -- volt-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > > and follow the instructions there. > > -- > > Ian Johnston > www.ianjohnston.com > https://www.youtube.com/user/IanScottJohnston > /"Because it feels good to make stuff!"/ > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ > 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.
