[EMAIL PROTECTED] wrote: > > The problem is that this change won't be reflected immediately. Even > if I 44105 Hz is exactly in sync with the peer, when I do another NTP > exchange in 2 seconds, it won't have enough time to compensate for the > existing offset so I may still calculate an offset of say 4 Hz then 3 > Hz in another 2 seconds, etc. By the time I get to 0, I may have set > my frequency to 44115 Hz and now it's too fast so it'll start getting > negative offsets. And it cycles back and forth like that because I'm > not taking into consideration the relative change.
You have to damp the loop, the same as you have to damp the suspension in a car. The general form of a commodity industrial controller involves adding proportional, differential and integral terms, hence they are called PIDs. You stop the overshoot by adding a term based on rate at which you are changing the value. There is particular level of correction that produces the fastest convergence without any over shoot. Although I forget it, the actual formula is high school level mechanics. You don't need an integral term, because you are not trying to zero the phase error. _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
