From: Lee Ritchey ([email protected])
Date: Thu Jan 06 2000 - 14:57:10 PST
The building of a PCB to test the simulation results is exactly the right next step. I've tried for years to find anyone who had actual test results to
support the 20h rule. The result is always the same- no one can support the rule with anything more than conjecture. Not much of an engineering approach
to rule making, I'm afraid.
Lee
Doug Smith wrote:
> Hi Jon,
>
> I would tend to build up a test board to try something like this. I
> learned a long time ago not to trust simulators unless I could build (or
> calculate by hand if possible) a similar but simpler test case and get
> the simulator to agree with calculations or measurement. I build a lot
> of test circuits and do measurements on them. I call that "putting the
> problem on the analog computer." Many of the test boards or other
> apparatus I build eventually end up in published papers or my courses as
> demos.
>
> I have seen cases where simulation output was believable, but not
> accurate because of some problem, either an input problem (garbage in ->
> garbage out) or a problem within the simulator itself.
>
> Given the above, does anyone know of any "hard" data to support the
> simulation?
>
> DougS (as opposed to DougM who posted the original 20H item)
>
> Jon Powell wrote:
> >
> > Doug Wrote:
> > Screwy SI Concept #2: The 20H Rule
> >
> > Why It's Screwy: Highly debatable concept and it's
> > not really an SI concept at all.
> >
> > Why It's Hung Around: Easy to remember
> >
> > Jon Writes:
> > About 6 months ago I did a test to see what was going on with this "20H"
> > rule. I simulated some simple ground planes with simple sources using a
> > 3D simulator. (I am not making any claims, just telling what I saw), the
> > results: the 20H boards quickly put all of their energy into the
> > enclosure. And the regular one retained the signal (a lot longer) Now,
> > perhaps this doesn't sound like I needed a simulation to know this but
> > this is my guess:
> >
> > 1) If you have a good enclosure, (or don't care about EMI off the board)
> > th 20H rule can reduce noise on the board. (And perhaps EMI off the
> > connected cables?)
> > 2) If you don't have an enclosure, and you care about EMI off the board,
> > the 20H rule may not be a good thing.
> >
> > --
> > Jon Powell
> > Director of HSSD Consulting Services
> > Viewlogic Systems, INC.
> > 805 988 8250
> >
> > **** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list
> > ****
>
> --
> --------------------------------------------------------------------
> ___ _ Doug Smith
> \ / ) Manager EMC Development & Test
> ========= Auspex Systems
> _ / \ / \ _ 2300 Central Expressway
> / /\ \ ] / /\ \ Santa Clara, CA 95050-2516
> | q-----( ) | o | Phone/FAX: 408-566-2157/2020
> \ _ / ] \ _ / Email: [email protected]
> --------------------------------------------------------------------
>
> **** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
> si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list
> ****
**** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list
****
This archive was generated by hypermail 2b29 : Thu Apr 20 2000 - 11:34:28 PDT