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
-----Original Message-----
From: john backus [mailto:34ford@msn.com]
Sent: Monday, December 10, 2001 10:57 AM
To: landspeedracer; Albaugh, Neil; land-speed
Subject: Re: Traction & Slipage
This one I can answer from experience. In the late 80's Corvette decided to
have a tv game dash. It included digital readouts for speed and rpm's, it
also had a sort of bar graph to show both. It really sucked! I also traded
for a '37 Packard street rod sedan delivery that had Dakota digital gauges
and the tach was useless except at idle or steady throttle running. I would
not recommend digital gages- although I believe Indy and F-1 cars use
them????
John
----- Original Message -----
From: landspeedracer
Sent: Saturday, December 08, 2001 8:31 AM
To: Albaugh, Neil; land speed list
Subject: Re: Traction & Slipage
Yes, but could the drivers human eye keep up with the tach moving that fast.
Especially if it was digital?
john
----- Original Message -----
From: "Albaugh, Neil" <albaugh_neil@ti.com>
To: "'landspeedracer'" <landspeedracer@msn.com>; "land speed list"
<land-speed@autox.team.net>
Sent: Friday, December 07, 2001 7:06 PM
Subject: RE: Traction & Slipage
> John;
>
> The limiting factor in your tach display was probably the mechanical time
> constant of your tachometer's meter movement-- not its electronics. An
> electonic tach indicator (LED, LCD, CRT, etc) could follow those fast RPM
> jumps but I don't know if anyone makes one (yet).
>
> Regards, Neil Tucson, AZ
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