[time-nuts] Achieving maximum performance when driving 5370A/Binputs

Dave hartzell hartzell at gmail.com
Mon Mar 1 04:04:39 UTC 2010


Thanks for the tips John.  Do you use the 50 ohm or 1M ohm settings with the
TADD-2?

Dave


On Sun, Feb 28, 2010 at 7:42 PM, John Miles <jmiles at pop.net> wrote:

> What threshold are you using?  If you leave it set to preset/0 volts, you
> may find that crosstalk between outputs on the TADD-2 cause false
> triggering.  I usually use the divide-by-10 setting with the threshold set
> to about 0.25V.
>
> It also helps to remove the jumpers from any outputs on the TADD-2 you
> aren't using.
>
> -- john, KE5FX
>
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> > Behalf Of Dave hartzell
> > Sent: Sunday, February 28, 2010 7:28 PM
> > To: Discussion of precise time and frequency measurement
> > Subject: Re: [time-nuts] Achieving maximum performance when driving
> > 5370A/Binputs
> >
> >
> > Today I have been trying to drive a 5370B directly from a TADD-2, with
> > little luck (other HP freq counters seem to work OK).   I was about to
> ask
> > about it on this list, but noticed this thread.
> >
> > I guess this could explain why I am getting erroneous, random readings?
> >
> > Dave
> >
> >
> >
> > On Sat, Feb 27, 2010 at 4:01 PM, Bruce Griffiths
> > <bruce.griffiths at xtra.co.nz
> > > wrote:
> >
> > > The attached excerpts from the 5370A and 5370B manuals indicate that
> for
> > > best performance, that the common practice of driving the
> > 5370A/B 1x inputs
> > > directly from a 5V CMOS logic signal is a bad idea.
> > >
> > > For the 5370A attenuating the 5V CMOS signal to a 1V swing with the
> > > threshold set to 0.5V is close to optimum.
> > > An input signal with limits of 0V and +1.4V with a trigger threshold of
> > > 0.7V is the maximum usable (for high performance).
> > > An input signal with limits of 0V and +0.3V with a trigger threshold of
> > > 0.15V is the minimum usable (for high performance).
> > >
> > > For the 5370A attenuating the 5V CMOS signal to a 2V swing with the
> > > threshold set to 1V is close to optimum.
> > > An input signal with limits of 0V and +3.5V with a trigger threshold of
> > > 0.7V is the maximum usable (for high performance).
> > > An input signal with limits of 0V and +0.3V with a trigger threshold of
> > > 0.15V is the minimum usable (for high performance).
> > >
> > > Bruce
> > >
> > >
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