ESC filters

[Peter Gargano]

Marc Randolph wrote:

> Any ideas on identifying what any of the numbers mean or which ones
> may be plug in replacements for others?  Just how many different
> ESC's can GM really have?

I think the only way to effectively ID an ESC Knock Filter
is to measure it's frequency response.

A while ago I wrote a simple program (for Bruce, around January, 
I recall, that I posted here) that used an XT laptop (ie. any 
desk/lap-top over XT speed) to generate an ESC REFerence signal. Using
this same technique, it should be possible to write some code that
produces a sweep frequency from say 500 Hz to 20 kHz. Using a 
PC parallel port, with passive circuitry that would constitute 
a crude three or four bit D to A converter, and some capacitors
for smoothing, the idea is to feed the resulting (crude) variable
frequency sine wave into the knock sensor. A simple four or five 
bit A to D converter (just a bit more complex that the D to A) gets
the output of the knock sensor back to the PC for measurement (I'm
assuming the knock module's output is analogue, although it's fed
into a counter bit in the GM P4's TPU).

The software, with junk box A/D and D/A converter, could generate 
a knock sensor frequency response graph (perhaps eXcel output?) that
should be able to be used to ID and compare different module.

Anyway, I have too many things on my plate at the moment, so this
isn't something I'll be following up any time soon. But if anyone
is interested, has the electronic and/or software skills, I'd be
happy to provide limited assistance.

Ideas?

Peter.

PS. Sure, there are other ways to do it - use a sound card to generate
AND read the signals, etc., etc. - my way, it doesn't require windows
(or intimate knowledge of your sound card h/w), and seems to me a more
reproducible way of generating a frequency plot.
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