Knock Sensors

[Frederic Breitwieser]

Yes, that's assuming they are an electret microphone.  I'm assuming they 
are, for there is a voltage present across the "out" lead and the engine 
block, of about 3 volts on mine Lincoln, which is typically a good 
indicator of an electret microphone (I use electret mics inside drum shells 
for recording all the time).

Piezo/crystal mics are only polarized if you are using the element as a 
speaker, not a microphone, however construction of the unit makes one side 
the ground (the larger plate the crystal is attached to).

On Friday, May 02, 1997 10:12 AM, Tom Cloud 
[SMTP:cloud at peaches.ph.utexas.edu] wrote:

> this is assuming that the mic is an electret mic (is it ???).
> If it is just a dynamic or crystal (piezo) and has no active
> impedance matching drivers inside it, it should not be polarized.
> (reason I question whether it's an electret is that all electrets

>  ... from one who knows lots about mics, and n-nnothing about knock
> sensors -- but wants to

Same here my friend :).

Frederic Breitwieser
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