E 420 (210.072) V8-4.2L (119.985) (1997)
A16
Knock sensor
a
Signal pattern in the case of controlled combustion
b
Signal pattern in the case of uncontrolled combustion (knocking)
c
Oscilloscope
t
Time
U
Electrical voltage
Any vibrations which occur are converted with the aid of the piezo ceramic into electrical signals.
Piezo-electric effect: If a mechanical force acts on a crystal, electrical voltages are produced.
Note: Knock sensor signals may also indicate engine damage, e.g. increased engine noise resulting from a widened piston groove.