[volt-nuts] Low noise reference

[Andre]

Yes I have relevant experience with Lifters, fingerprints generally are a nightmare.

May also be worth mentioning that different grades of IPA are more or less useful, it absorbs water
in its pure form so this needs to be taken into account.
Use "no clean" fluxed solder if possible as it works well.

Also relevant, don't forget that NASA like using splice joints where the wire is tied into essentially a reef knot.
This is for all sorts of reasons not least visual inspection of the joint at regular intervals and anti-
vibration measures are used like clear heatshrink.


________________________________________
From: volt-nuts <volt-nuts-bounces at febo.com> on behalf of Poul-Henning Kamp <phk at phk.freebsd.dk>
Sent: 17 February 2018 09:10
To: Discussion of precise voltage measurement; Randy Evans
Subject: Re: [volt-nuts] Low noise reference

--------
In message <CANwu9JY-_o80YoeN_-hnXFxsYuQ=VKON0yw_RoovEGjhh3hHSA at mail.gmail.com>
, Randy Evans writes:

>I was concerned about the leakage through R1-C1.

Ideally there should not be any voltage across C1 because C2 "bootstraps"
it, so C1's leakage resistance should not matter at all.

>In all cases the leakage, as measured with a
>Keithley 414 picoammmeter, showed a leakage or around 0.08 uA at 10V

That kind of currents take you into the territory where there are
no insulators, only conductors which are not very good at it, such
as expoxy, air, humidity, fingerprints etc.

The very first thing you want to do, is wash your entire construction
in isopropanol[1].

The next thing you want to do is make sure you are not fighting a
an electrostatic phenomena:  Only measure inside a grounded metal
enclosure.  Cookie tins work great.

Finally make sure you are not measuring Seebeck/thermo-electric
phenomena:  Measure while you raise and lower the temperature
of the hole thing and look for gradients.

>I also tried a 0.68 uF polystyrene capacitor and also saw leakage current
>variations, although much less than the electrolytic and tantalum
>capacitors, as one would expect.

I actually have in mind to buy a couple of the cheapest "teflon"
capactors from the audiohomøopathy world, and see if that is
really what it claims to be.

Poul-Henning

[1] I've been told that the liquid used in dishwashers to avoid
spots on glass, a mixture of soaps and alcohols, is also good for
electronics, but I have not tried it.

--
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
_______________________________________________
volt-nuts mailing list -- volt-nuts at febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.