Jerry, for a 100MHz PIC based counter a prescaler will be necessary. But it will not be necessary for a 30MHz counter.
Prescalers do not have to be by divisors of 10. I recall the PIC counter input to be good to 50MHz so the prescaler could just be a divide by two if you need a 100MHz counter and it *has* to be done by a PIC. Of course there are lots of logic families that don't need a prescaler at 100MHz and could be used to make a frequency counter. Most frequency counter designs out there on the net introduce an extra count or two due to flawed conception of gate. Tim N3QE Sent from my VAX-11/780 > On Apr 23, 2017, at 9:25 PM, Jerry Hancock <[email protected]> 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 -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
