> >  I'm not sure about the implementation, but what about a switched capacitor
> > filter for the bandpass (just a suggestion, since I#ve never worked with
> > either analog multipliers or switched cap filters) ? Of course this will
> > (like the multiplier setup) only be feasible if your input signal is
> > constant during the time needed to sweep the filter.
>
> Good point about the signal being constant.  Since I'll be looking at the
> signal from an accelerometer on an engine, I'm sure the signal will not
> be constant.
>
> Yours,
> --
> Derrick Early
> early@finite.nrl.navy.mil
>
I tried to reply to you earlier but I think I've got an email problem.
Anyway, iff you decide you need to do some external processing it sounds
like you could do worse than have a look at Harris Semiconductor's
HIP9010 which is described as an "engine knock signal processor". It's
designed to be connected to a microprocessor as part of an engine
management system. If you don't know any Harris reps you can always get
in touch with them via their web page at:

        <URL:http://rel.semi.harris.com:80/>

They've got some data sheets online as well, although I can't guarantee
that will be one of them! Cheers.
                                                -Alasdair

[ The opinions expressed are my own and are therefore undeniably correct ]
[ beyond a shadow of a doubt.                                            ]

Alasdair MacLean, University of Edinburgh, Dept. of Artificial
Intelligence, 5 Forrest Hill, Edinburgh, EH1 2QL
tel. (+44) 0131 650 4497        fax. 0131-650-6899
email alasdair@aifh.ed.ac.uk
<URL:http://www.dai.ed.ac.uk/staff/personal_pages/alasdair/index.html>