Reciprocal counter where one measures the period of the output of a divide by N and then takes the reciprocal of this period multiplied by N as the frequency of the divider input. With a 100MHz clock one can achieve ~ 0.01ppm resolution for a 1 second averaging time. if one uses interpolators with 100ps resolution (equivalent to a 10GHz clock) the resolution improves to ~0.1ppb for a 1s averaging time.
Bruce > > On 24 April 2017 at 13:25 Jerry Hancock <je...@hanler.com> wrote: > > For some reason I am not getting the individual emails so I apologize for > not replying more promptly. I’ll have to check my profile. > > As far as I can tell from the notes, and by the way, the number of notes > was why I was trying to move this off list, to get to .001hz I need to > measure over 1000 seconds. This is ok. Since I am looking for an average over > time anyway, this is not a problem. By the way I am using a GPSDO and planned > to use it divided down for the gate. > > The only reason I mentioned a prescaler was that there was a 12 digit > counter schematic on the web that looked pretty complete. This person used a > prescaler and I was trying to wrap my head around how this helped with > resolution and I guess from the replies, that is not a practical solution > (using a prescaler) when you want high resolution unless I use the inverse > operation which I can’t remember what it is called off the top of my head. > > I’ve seen some HP 12 digit counters but since I have a GPSDO and who > knows how many micro development boards around here, I thought I would take a > run at it. > > So to summarize, if I limit my high resolution to 99,999,999.999hz and > use a gate of 1000 seconds, would that get me to .01hz? If not, then what > would the possible resolution be? > > Thanks for all the input, very helpful. > > Jerry > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
