[time-nuts] Counter display resolution

Mike Feher mfeher at eozinc.com
Sat Dec 22 12:26:13 UTC 2007


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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