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

John Miles jmiles at pop.net
Mon Mar 1 03:42:01 UTC 2010


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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