[SI-LIST] Re: Split gnd planes - for/against?
- From: steve weir <weirsi@xxxxxxxxxx>
- To: "Kevin G. Rhoads" <kgrhoads@xxxxxxxxxxxx>
- Date: Wed, 08 Apr 2009 11:49:34 -0700
Kevin, PCB E/M software 10 years ago could frequently give squirrely
results. An understanding of the software and sanity checks on results
are still requisite. But the various products out there frequently
deliver results that correlate to measurements for the problems we work
with deadly, and I do mean deadly accuracy.
When we run into something that doesn't seem reasonable from a tool we
validate in one or more of several ways including running the problem on
tools from multiple vendors, and creating measurement test vehicles.
We follow these practices and haven't found our trousers around our
ankles yet.
Steve.
Kevin G. Rhoads wrote:
>> If building multiple prototypes gets you through your day that's fine.
>> It is something we work hard to avoid the need for. The tools exist to
>> evaluate pretty much anything we want to know about layout performance
>> before we commit to fab.
>>
>
> I started out with an S.B. in theoretical mathematics, before switching
> to EE for grad. school. I've done theoretical analyses, numerical
> analyses (both with commercial and with homebrew codes) as well as building
> stuff.
>
> Simulation and analysis tools are great. But I've seen too many cases where
> reality is different enough that I don't trust predictions. That may be
> because all too often I am working with projects that are extreme in one
> way or the other. (E.g., mMeasuring conductivity of molten glass [+/-0.5%],
> dielectric constant of cryogenic organic solvent mixtures, things that
> involve
> dual electrometers, and more recently ion and electron detectors for rockets
> (those are actually fairly straightforward).)
>
> So it may be that my experience is non-typical enough not to be a good
> guideline, but I don't trust simulations. I've had too many
> cases where some critical parasitic or minor effect is not modelled
> well enough and the simulation and the reality are more orthogonal
> than similar.
>
> So just call me "once bitten, twice shy"
>
>
--
Steve Weir
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