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:[email protected]> Skickat: den 3 juni 2016 20:42 Till: [email protected]<mailto:[email protected]> 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: [email protected]<mailto:[email protected]> > Skickat: den 26 maj 2016 13:35 > Till: [email protected]<mailto:[email protected]>; > [email protected]<mailto:[email protected]> > 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:[email protected]] > To: [email protected] > 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 -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ > volt-nuts mailing list -- [email protected] > 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 -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
