Bruce, thanks for the tip on the anti-charge injection LP filter. Actually, early on, I put a 0.1uF cap across the EFC line on the osc, support board, so there is some LP filtering working there. But my old Tektronix "prayer wheel" Circuit Computer says that's only a 5ms TC -- prolly need quite a bit more or else buffer the EFC line from the DPM.
Best, Dick Moore On Oct 31, 2008, at 5:56 PM, [EMAIL PROTECTED] wrote: > ------------------------------ > > Message: 6 > Date: Sat, 01 Nov 2008 11:00:59 +1300 > From: Bruce Griffiths <[EMAIL PROTECTED]> > Subject: Re: [time-nuts] OFC OCXO > To: Discussion of precise time and frequency measurement > <[email protected]> > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=ISO-8859-1 > > Richard Moore wrote: >> Hi Ernie -- thx for the feedback. I have had all of those effects and >> more with an HP10811A and an EG&G Cinox version of the 10811A, so I >> won't be surprised to see such things with this one either. I'm going >> to try it with Bert Zauhar's FLL controller to see how it runs. You >> can visit my experience to date at: >> www.moorepage.net/gps2.html >> >> I'll update the site again after I run the OFC for a while. >> >> Best, >> Dick Moore >> > Dick > > The usual way of reducing charge injection transients from a DVM into > the circuit being measured is to use an RC low pass filter between the > circuit and THE DVM. > Charge injection can be somewhat larger for those autozeroing DVMs > that > do not use a precharge amplifier to reduce the effect. > panel mount DVMs do not usually have a precharge amplifier. > > With a low pass filter it may be possible to reduce the value of > the 50K > isolation resistor that you used. > The value is relatively high because it relies on the DVM and wiring > capacitance as the capacitive part of the RC low pass filter. > > Bruce > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
