Re: help! how do I formulate this sampling system and analyze it?

Jerry Avins wrote:

Tim Wescott wrote:

  ...

Actually my favorite data acquisition system for high-performance control is to average the input for one sampling period. This puts notches at all of the harmonics of the sampling rate, so anything that might alias down into the passband of my control system gets killed dead. There's a phase penalty, but it's smaller than anything else that'll do that for me. Aside from the amount of delay (or advance) in the integrator that's pretty much what Lucy's system is doing.


It lets the cat out of the bag, but I can't resist. That's exactly what an integrating converter does for you.

Jerry

Yes it is. Most of the stuff I've used the above technique with, however, are closing the control loop at more than 5kHz. The only ADCs that I know of in that sort of frequency range are sigma-deltas and SARs. The sigma-deltas are all for audio; they are unspecified for DC performance and for delay (but I assume the delay is huge relative to their pass frequencies). At any rate I have ended up doing it by oversampling at 4x to 16x and summing.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
.

Relevant Pages

  • Re: help! how do I formulate this sampling system and analyze it?
    ... control is to average the input for one sampling period. ... This puts notches at all of the harmonics of the sampling rate, so anything that might alias down into the passband of my control system gets killed dead. ... The sigma-deltas are all for audio; they are unspecified for DC performance and for delay. ...
    (comp.dsp)
  • Re: help! how do I formulate this sampling system and analyze it?
    ... control is to average the input for one sampling period. ... This puts notches at all of the harmonics of the sampling rate, so anything that might alias down into the passband of my control system gets killed dead. ... The zero-order hold ADC and the integrating ADC require identical compensation at high frequencies and no compensation at all for low. ...
    (comp.dsp)
  • Re: help! how do I formulate this sampling system and analyze it?
    ... control is to average the input for one sampling period. ... This puts notches at all of the harmonics of the sampling rate, so anything that might alias down into the passband of my control system gets killed dead. ... Aside from the amount of delay in the integrator that's pretty much what Lucy's system is doing. ...
    (comp.dsp)
  • Re: 8 bit microcontroller market
    ... The nice and fancy solution is not necessarily ... Reducing "phase delay" between observation and control is important. ...
    (comp.arch.embedded)
  • Re: 20 sec delay opening tcp connection from within IE hosted cont
    ... embedded WinForm control (to run inside Internet Explorer). ... This delay ONLY ... IOException("Could not connect: connection timed out") ...
    (microsoft.public.dotnet.framework.aspnet)