On Monday, June 04, 2012 08:01:51 AM andy pugh did opine: > On 4 June 2012 07:26, gene heskett <ghesk...@wdtv.com> wrote: > > It is extremely sensitive to this bit of timing variation caused > > by a nominally 5 thou non concentricity in the way it is mounted (I > > believe because the center hole in the disk is slightly undersized, > > forcing one side of the hole to be pulled into the threads valley) > > both in duty cycle AND quadrature accuracy else the > > encoder.N.velocity output contains noise that at best is +- 50% of > > its average value despite the fact that even in the degraded state, > > it can still follow the spindle at 50 RPS! > > Feed-per-rev mode uses the velocity output, but threading only uses > the position output, so shouldn't really care about noise on the > velocity pin. > > I can't help feeling that a low-pass might help. > I had one in there for a while, wasn't much help & did seem to give a feedback pole that boosted any oscillation tendencies. I tried multipliers from .25 all they way out to .01, but according to halscope, the output slew rate nor the noise was being filtered in the manner I was looking for.
> However, I also have noticed how noisy that velocity pin is. Perhaps > it is worth having a look at that anti-quatisation code to see if it > works properly. That would be much appreciated Andy, thanks. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> "I once witnessed a long-winded, month-long flamewar over the use of mice vs. trackballs...It was very silly." (By Matt Welsh) ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
