Propeller speed and phase sensor

Abstract From the Canadian patent

A speed and phase sensor for counterrotating aircraft propellers is described. A toothed wheel is attached to each propeller, and the teeth trigger a sensor as they pass, producing a sequence of signals. From the sequence of signals the rotational speed of, each propeller is computed based on the time intervals, between successive signals. The speed can be computed several times during one revolution, thus giving speed information which is highly up-to-date. Given that the spacing between teeth may not be uniform, the signals produced may be nonuniform in time. Error coefficients are derived to correct for nonuniformities in the resulting signals thus allowing, accurate speed to be computed …