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From: ISW@cup.portal.com (Isaac S Wingfield)
Newsgroups: sci.electronics
Subject: Re: ESR of copper oxide rectifiers
Message-ID: <25045@cup.portal.com>
Date: 15 Dec 89 04:56:31 GMT
References: <1989Dec12.022128.3128@tapa.uucp> <3103@tymix.UUCP>
  <8974@cbmvax.commodore.com> <10440@ucsd.Edu>
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Brian Kantor writes:

>Probably the simplest way to simulate the voltage drop of the old
>copper-oxide rectifier is to series several silicon diodes.  That
>way you'll have a relatively constant voltage drop despite a varying
>load, which a resistor would not give you.
>       - Brian

I'm not sure that is a good simulation; my vintage 1951 Simpson VOM
uses a copper oxide bridge on the AC ranges - so did all VOM's for
many years. Working from memory, I believe CuO rectifiers have:

   Low forward conduction drop  (necessary for good VOM performance)

   High series resistance  (not a problem in VOM's)

   Poor high frequency response - cutoff around 100 kHz, I think

   Low reverse blocking voltage

I'd try just one Si diode, and add a series resistor if necessary.

I believe CuO devices were used in "Varistors" also; low FCD would
be desirable here.

Happy holidays
Isaac
isw@cup.portal.com