Hi

Is the knock sensor output an A/C? i.e. V+ to V- or is it A/C form but only V+, meaning "above zero voltage"?

And while we are at it. I cars, does the ECU use its frequency or its amplitude to sense a knock?

thx

 

AC. It is a plain microphone and nothing else at all. In a sturdy housing , usually with a sturdy price.

Depending on manufacturer, will be a piezoelectric, or a condenser, or whatever they want to do, for the corresponding ECU circuit to match it.

Have to sense amplitude, as the detonations sensed can vary in frequency as there is many noises emitted by the engine and their cadence varies on RPM. Have to be equally detected even if happen at low or high rpm.

 

It can get more complicated. It is best to window the knock observation about the combustion event. This helps reject other engine noises.