[time-nuts] Counter display resolution

WB6BNQ wb6bnq at cox.net
Sat Dec 22 15:23:30 UTC 2007


Hi Mike,

Thanks for the explanation.  As I do not own a "reciprocal" counter, I was
unfamilar or had forgotten the issue you described.  "Reciprocal" was the missing
link !

Bill....WB6BNQ

Mike Feher wrote:

> Bill -
>
> Sorry if I was vague. I am assuming that the frequency read out is the
> frequency in the display, and, not one over the bus. Regardless of the fact
> that the counter is auto scaling or not, they can only display a fixed
> number of digits. I am also assuming that these are reciprocal type of
> counters. So, given a fixed time base, and a fixed number of digits, if the
> delta f measured is above 10 MHz, then with a 11 digit display, you would
> read 10,000,000.000 Hz plus the offset from that number. So, the observable
> delta f would be at best in the 0.000 Hz range. Now, if the frequency
> measured was slightly below 10 MHz, you would be able to display up to
> 9,999,999.9999 Hz. I am not considering any averaging at this time, just
> what is displayed. So, in this case you should be able to measure down to
> 0.0000 Hz delta f. Hence my statement of the extra LSD being shown. This has
> been my experience. Regards - Mike
>
>
>
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960
>
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of WB6BNQ
> Sent: Saturday, December 22, 2007 7:00 AM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] Counter display resolution
>
> Mike,
>
> Your statement about "counters" is rather general and misleading.  You need
> to
> explain your comment better.
>
> For instance, are your referring to the input signal or did you mean having
> the
> internal reference frequency  offset from a standard value ?  All the
> counters I
> have do not "auto-scale" which is what it sounds like your counter is doing.
> However, you do not mention the word "scaling" or "auto" in your statement.
>
> In all of my counters the digits displayed is what you get no matter what
> frequency is being observed.  There is no gain in resolution by being
> slightly
> lower then or any loss by being higher then some arbitrary point.
>
> For the sake of the less skilled that might be on the list -server, could
> you
> explain in more clear detail what you were eluding to ?
>
> Thank you ... Bill....WB6BNQ
>
> Mike Feher wrote:
>
> > Bob -
> >
> > With most counters, I have found that running them at slightly less than
> 10
> > MHz gives you an extra displayed digit of resolution. If the "1" out of 10
> > MHz were to be displayed, it would take up one more digit in the MSD
> > position, leaving you one less in the LSD position. Since the numbers are
> so
> > close anyway, if measuring for stability, I personally would prefer that
> > extra digit in the LSD position. Regards - Mike
> >
> >
> >
> > Mike B. Feher, N4FS
> > 89 Arnold Blvd.
> > Howell, NJ, 07731
> > 732-886-5960
> >
> >
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> > Behalf Of Robert E. Martinson
> > Sent: Saturday, December 22, 2007 1:57 AM
> > To: 'Discussion of precise time and frequency measurement'
> > Subject: Re: [time-nuts] HP 5370B question
> >
> > I ran my 5370B for one hour, counting its own reference with a one second
> > gate.  The summary of the results are:
> >
> > min     9999999.99650  Hz
> > max     9999999.99963  Hz
> > avg     9999999.99796  Hz
> > median  9999999.99787  Hz
> >
> > Per the manual's  Performance Test 5 (page 4-12) the spec is +/- 0.005 Hz.
> > It would be nice if my average was 10,000,000.000 HZ but??  From a
> Time-nuts
> > thread of several months ago, the adjustment for this result is very
> touchy
> > and it's likely you will make the result worse rather then better.  Since
> > mine is in spec, I'll leave it alone.
> >
> > I have sent the graphical & raw data to Corby, if anybody else is
> interested
> > please advise me of your email address.
> >
> > Regards,
> > Bob Martinson, N1VQR
> >
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> > Behalf Of corby d dawson
> > Sent: Wednesday, December 19, 2007 2:15 PM
> > To: time-nuts at febo.com
> > Subject: [time-nuts] HP 5370B question
> >
> > Hi,
> >
> > Could a few of the 5370B owners connect the counters reference output to
> > its counting input jack and with a 1 second gate let me know what the
> > last 2 digits are doing?
> >
> > An earlier post implied that the last couple digits will wander around
> > due to the way its designed.
> >
> > I'd like to know what a couple different counters show to see if that is
> > indeed true!
> >
> > Thanks,
> >
> > Corby Dawson
> >
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