Hi Unless you can include all the second and third order effects in your model, there will still be a lot to “learn” as you build your gizmo. Computing power is still impacted by garbage in / garbage out.
Bob On Mar 23, 2014, at 12:07 PM, Don Latham <d...@montana.com> wrote: > I agree.. Had a maybe weird thought. Computing power is now a trivial part > of the "problem", in that a Ras.Pi can be put to the task for $35 or so. In > that case, PIDdling with time constants and such in a feedback loop with phase > difference as the error signal is easily done, either in simulation, or for > real, as you point out. So, since ADEV or one of its brothers is the measure > of success of PIDdling, shouldn't the ADEV or brethren be in some way the > error signal for the whole? For example, how about a TCGPSDO? put the whole > thing in a first-order thermal enclosure, with power-over-ethernet being the > only external wiring? > Hope I'm at least making at least logical sense… > > Don > Tom Van Baak >> Hi Don, >> >> Yes, easy! And that's exactly the idea -- to take real inputs (or borrowed >> copies of real inputs), and a real software algorithm, and measure the >> virtual >> output to see how well your algorithm and tunable parameters work. Tweak >> parameters. Evolve the algorithm. Simmer until well done. >> >> Theoretically, after one builds the real GPSDO, using the same code or at >> least the same algorithm, the actual performance should nearly perfectly >> match >> the simulation. >> >> The difference, at least for me, is that I'd rather play with unix commands >> and C code on a PC, trying things out in a matter of minutes, than spend >> weeks >> slowly trying different things with a real GPSDO (which I've also done). In >> addition, I think gpsim1 makes a useful, almost interactive, teaching tool. >> >> Now, no simulation is perfect. But oscillators, dividers, 1PPS comparators, >> and DACs are not really that complicated. You are probably guessing that I'm >> working on gpsim2 which will allow simulation of phase and frequency jumps, >> varying GPS reception, power-up, cold-boot, warm-boot, holdover, thermal or >> mechanical shocks to the instrument, and other events that I see in real >> life. >> >> But let's let gpsim1 run its coarse before we worry about 2nd order effects. >> I'm very interested in alternative or enhanced algorithms that people come up >> with. The two algorithms now in gpsim1 and default tuning parameters are just >> something I threw together in a few minutes. >> >> /tvb >> >> ----- Original Message ----- >> From: "Don Latham" <d...@montana.com> >> To: "Discussion of precise time and frequency measurement" >> <time-nuts@febo.com> >> Sent: Saturday, March 22, 2014 8:18 PM >> Subject: Re: [time-nuts] GPSDO simulation tool >> >> >> Hi Tom et.al. Isn't the simulator "easily" convertible to the real thing? >> That is, data inputs should be convertible somehow to data streams from >> physical devices? >> Don >> >> >> >> _______________________________________________ >> 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. >> >> > > > -- > "The power of accurate observation is commonly called cynicism by those who > have not got it." > -George Bernard Shaw > > > Dr. Don Latham AJ7LL > Six Mile Systems LLC > 17850 Six Mile Road > POB 134 > Huson, MT, 59846 > VOX 406-626-4304 > Skype: buffler2 > www.lightningforensics.com > www.sixmilesystems.com > > > _______________________________________________ > 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.