Does any of the Volt-Nuts brain trust have any experience adding an external Frequency Reference on the 3458A. There is a 20MHz reference on the A/D board but externally clocking it has affected linearity collecting data off a 10VDC reference that looks a little like a hanging bridge I have seen before between GPS and oscillator sync. Is there another clock? Thanks for any thoughts. Thomas Knox

What do you hope to gain by having a more stable clock? On Fri, Jun 5, 2015 at 10:01 AM, Tom Knox <actast@hotmail.com> wrote: > Does any of the Volt-Nuts brain trust have any experience adding an > external Frequency Reference on the 3458A. > There is a 20MHz reference on the A/D board but externally clocking it has > affected linearity collecting data off a 10VDC reference that looks a > little like a hanging bridge I have seen before between GPS and oscillator > sync. Is there another clock? Thanks for any thoughts. > > Thomas Knox > > > > _______________________________________________ > 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. > -- *John Phillips*

-------- In message <COL130-W405514A623341979406897DFB20@phx.gbl>, Tom Knox writes: >Does any of the Volt-Nuts brain trust have any experience adding >an external Frequency Reference on the 3458A. The only reference I have seen to this is that NIST modified a HP3458A this way in order to be able to sample a sine-wave approximation from a Josephson junction voltage standard after the transitions had settled. >There is a 20MHz reference on the A/D board but externally clocking >it has affected linearity collecting data off a 10VDC reference >that looks a little like a hanging bridge I have seen before between >GPS and oscillator sync. Is there another clock? Thanks for any >thoughts. You want to be 100% sure you don't inject any ground reference into the A/D board. Whatever you do, you *must* isolate the signal. Agilent isolated the serial port between the A/D and the main processor with 20cm of (plastic) optical fiber, and I think a significant clue should be taken from that: Optocouplers and transformers are unlikely to be good enough. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@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.