Image Number 2 for United States Patent #5581016.
A detonation detection system for internal combustion piston engines which senses pressure within each cylinder through a piezoelectric force transducers installed under each spark plug producing pressure charged signals which signal is converted from inline charge to voltage. The signal is then passed through a gating comparator which segregates out the low pressure signals associated with intake and exhaust strokes. The signal then passes through a high-pass filter which removes normal combustion pressures. The filtered signal is then processed through an RMS (root mean square) to a DC converter which continuously computes the instantaneous square of the input signal, averages it, and takes the square root of the result to provide a DC voltage proportional to the RMS of the input. The DC signal is then processed through a peak and hold circuit which holds the peak signal for an adjustable reset-time period. A digital display is provided for each cylinder which receives and displays in numerical value the peak RMS signal.