What sort of signal is the knock sensor?

[jsg at donet.com]

| By using the output of a HP3324A function generator connected to  DR 562
| knock sensor coupled with a 1/4 pipe to another DR 562 knock sensor I was
| able to track the freq. curve of the sensor. The sensor responds to

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| with a scope the DR 562 sweet spot was 6KHZ. A loud tone could be heard at
| 6KHZ indicating resonance.  7-10KHZ had good outputs. The voltage dropped
| off at 12 KHZ . An output was observed up to 50KHZ very small amplitude  4

Don, is this a resonance of your test setup or of the sensor? (i.e.,
if you double or halve the length of pipe, does it stay the same?)

john gwynne