Sorry, but there is no such thing as a "simple knock detector". You might as well be looking for the Holy Grail.
Remember: You are asking a circuit to detect knock that you can't hear, while ignoring engine noise that you can hear. And the input is essentially a microphone.
It...
The output of a resonant sensor is about 500mv/g, while that of a non resonant sensor is about 20mv/g.
An example of a non resonant sensor is the Bosch sensor, which requires a shielded cable.
Hi to all. My name is John Pizzuto, and I'm the designer of the J&S SafeGuard.
For a background on knock sensors, read SAE Technical Paper Series 900488, Combustion Knock Sensing: Sensor Selection and Application Issues
Authored by Steven M. Dues, Joseph M. Adams, and George A. Shinkle...