Well, it ain't MIL-SPEC but it works (mostly).
Regards, Neil Tucson, AZ
-----Original Message-----
From: Dave Dahlgren [mailto:ddahlgren@snet.net]
Sent: Monday, December 10, 2001 1:43 PM
To: Bryan A. Savage Jr
Cc: Albaugh, Neil; List Land Speed
Subject: Re: Traction & Slipage
Those cheap production electronics are the best money can buy!!
Dave Dahlgren
"Bryan A. Savage Jr" wrote:
>
> Neil, you have cut to the heart of the "driver - gage interface".
> Without substantial "low- pass filtering (smoothing)" or dampening,
> the gage is "faster than the eye can see".
> This smoothing or dampening is what has generated the myth about revving
> an engine without a load. I would set the rev limiter off (11,000) when
> clearing/blipping the engine and the tach never went over 6,000.
>
> How quick are electronics? Remember folks, OBD-II detects and identifies a
> misfiring cylinder by a change in angular velocity in part of one
> revolution. It then spends some time recording that information.
> And that's cheap production electronics.
>
> Bryan
>
> "Albaugh, Neil" wrote:
> >
> > John;
> >
> > The problem isn't in the fact that they're "digital"-- it's the
fundamental
> > design of the tach electronics & readout mechanism. Most tachs (analog
or
> > digital) are designed with so much low- pass filtering (smoothing) that
they
> > can't follow fast engine RPM changes very well. I suspect this is done
to
> > make the display look more steady to the average driver. There is one
> > limitation that affects some digital systems-- a fundamental limit
imposed
> > by sampling speed-- its Nyquist limit. There is no good reason to be
limited
> > by this these days. Even very high resolution ADCs and DACs can be
obtained
> > that have sampling rates approaching 100MHz. They can respond to RPM
signals
> > as fast as 20 billionths of a second. I had an '85 'Vette and I agree
with
> > you regarding its video game display instrumentation-- flashy- looking
but
> > poor response.
> >
> > Regards, Neil Tucson, AZ
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