Knock Sensors

[John Bertram]

At 09:11 AM 5/2/97 -0500, you wrote:
>>KNock sensors are basically a microphone, and most modern microphones are 
>>polarized, since they have two leads, one ground and one is the audio 
>>output and combined VCC in.
>
>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.


It is a piezo crystal... I just wasn't sure if it had a polarity. I assume
not since the connector for it can be turned upside down and plugged in,
reversing the polarity.

For more info on knock sensors (other than polarity), check out my APC site...
http://www.teleport.com/~bertram/volvoapc


John Bertram, Technician
Garry Small Saab
Volvo Turbo APC project (www.teleport.com/~bertram)
'87 Volvo 740 Turbo Sedan
'66 Rover TC 2000
'70 Toyota Corona Mk.I