Automatic Threshold Detection for Tachometer Signals

A method for deriving information from a tachometer signal, the method comprising:

• (a) sensing the tachometer signal;
• (b) taking a running derivative of the tachometer signal to generate a derivative signal;
• (c) determining a mean value and a standard deviation value of the derivative signal;
• (d) setting all negative values in the derivative signal to zero to generate an all-positive-value derivative signal;
• (e) finding N number of peaks in the all-positive-value derivative signal;
• (f) discarding statistical outlier peaks from the N number of peaks in the all-positive-value derivative signal, wherein the statistical outlier peaks have an amplitude greater than a sum of the mean value and the standard deviation value;
• (g) determining a characteristic of the all-positive-value derivative signal from which the statistical outlier peaks have been discarded;
• and
• (h) using the characteristic to determine one of the following:
• the tachometer signal is to be used to derive a threshold value for tachometer pulses in the tachometer signal;
• the derivative signal is to be used to derive a threshold value for tachometer pulses in the derivative signal;
• and
• a meaningful threshold value cannot be derived due to insufficient information in the tachometer signal.

A method for deriving information from a tachometer signal, the method comprising:

• (a) sensing the tachometer signal;
• (b) taking a running derivative of the tachometer signal to generate a derivative signal;
• (c) determining statistical characteristics of the tachometer signal and the derivative signal;
• and
• (d) deriving a threshold value for tachometer pulses in the tachometer signal based on the statistical characteristics of the tachometer signal and the derivative signal.