What do you know about a knock sensor?

[Mech_Mat]

ok, maybe it's just me, but is there a major shortage on gauges that can monitor knock sensors? I see them on ebay from boats, airplanes, and buick grand nationals.

From all of the reading I have done, a knock sensor is a pizeo style microphone. so, if i were to make a crappy little pre-amp circuit that will drive a led array, i might have something that shows knocks?

Does anyone know how the pcm aquates the knock signal? does it look for a fixed frequency, or pattern?

i got a good history with making small circuits like this, but i cannot find the enough information about knock sensors to start on it. it almost seems that the knock sensor is something thats not talked about as much as others.

[gouki9000]

there is a sticky on this section..... take a look