Re: Accurately measure C of electrolytic capacitors ?
From: Watson A.Name - \ (NOSPAM_at_dslextreme.com)
Date: 02/08/05
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Date: Tue, 8 Feb 2005 02:28:05 -0800
"gmv" <noemail@please.123> wrote in message
news:J7MNd.24453$C24.9065@attbi_s52...
>
> "Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com>
wrote in message news:110cnbn267cd7fe@corp.supernews.com...
> >
> > "gmv" <noemail@please.123> wrote in message
> > news:jJdNd.21541$C24.9629@attbi_s52...
> >> Interesting,
> >> I always thought the opamp buffered the output
> >> so you could hook it to anything between 2K
> >> and infinity.
> >> I will keep in mind what you have said.
> >> I have noticed a terrible ringing effect at Q
> >> 5 and above.
> >> Maybe that is what you are talking about.
> >> In any case I really need to see things between .5Hz
> >> and 2Hz. It is only the noise in my local area that
> >> keeps me from doing this as far as I can tell.
> >>
> >> http://home.mchsi.com/~gmvoeth/index.html
> >>
> >> will show a bit more of what I am doing.
> >
> > Buy the RS printed circuit board that has the same layout as the
> > breadoard. Build the circuit on that board, and put it inside of a
> > metal enclosure, so that most of the noise is kept out of the
circuit.
>
> What is "RS printed circuit board " ?
RS = Radio Shack AKA Radio Scrap, etc. They sell a PC board that has
the same layout as the breadboard. Makes it easy to transfer the
circuit to a permanent circuit board.
> I have settled on using only a single filter
> as is now posted to my web site. This will
> limit one to only seeing P waves but in
> this noisy environment it is the best I can do.
> I agree with everything you say except I can not
> put a preamp outside with the Geophone.
Well, that's probably the reason why you are getting so much noise!
> There is a circuit I have included not on the
> schematic and it is a 567 tone decoder on the back
> end to decode WWV calibration marks.
> Thanks for your advice, I can see a lot of
> common sense to it. But I still do not
> know how to buy a circuit board that already
> has my layout on it. I figure I will have
> to do the layout and etching etc... myself.
I'm not sure you understand. The hole patterns match those on the
breadboard.
Here it is, it's catalog # 276-170 and costs a bit over $3.
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fnam
e=CTLG%5F011%5F002%5F002%5F000&product%5Fid=276%2D170&MSCSProfile=745D84
CBF04D14A48AA6FF9C89D722C0BA68C1B04FE384678A5285FCD6E056B17AF21627FDABE3
16B90B3C038D68EBD6B7F9F3BD1712EAA9951ACB2590A05C6517EFE46941FEFDD1985D4E
FD6321F5E70B4DE9B6C1D45512DCD9FB3DBCACB9479D26760FAF1D7B193B4FEA078B5E09
80BDD61634ABB7D328B012D36915420A2B457BE162481F674B
> > All preamplification should be done as close as possible to the
> > geophone, to get the signal well above the noise _before_ it goes
any
> > distance.
> >
> > Filtering should be done at the other end, to get rid of noise in
the
> > long transmission line between the sensor and the PC.
> >
> > One other important point. The outside can of the electrolytic is
at
> > signal level, and is a large capacitance to the outside world. Just
> > shielding these from outside noise should help. You might consider
> > putting some aluminum foil over the ones at the input, and grounding
the
> > foil to common. Just to see how much it will help to put the whole
> > thing in an enclosure.
[snip]
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