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

Jerry Avins wrote:

Tim Wescott wrote:

Jerry Avins wrote:

lucy wrote:

Hi all,

This system consists of an DAC, a processor, and a ADC. The flow graph
is like as follows:

input-digital-signal -> DAC -> filter(Continuous Time) -> ADC ->
output-digital-sigal





That's a weird way to do things. Is it an academic exercise?

-snip-


Jerry



Actually that's the issue I face every single time I want to model a continuous-time plant from the point of view of my digital controller. There's a pretty direct solution (see my direct reply).


I hadn't realized it was for a simulation only. It would be weird for a final physical realization. Did you see my having-slept-on-it reply this morning? I hope Lucy did.

This is the only response from you that I see in this thread.

Jerry 

It took me 30 minutes to write -- you're just too fast.

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.

--

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

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