| 摘要 |
A tachometer system for an aircraft landing gear. The tachometer system comprises a tachometer arranged to generate a variable voltage signal in response to the rotation of a wheel of the aircraft landing gear, and a processing system arranged to output a speed signal indicative of the rotation speed of the wheel of the aircraft landing gear. The speed signal is determined from the variable voltage signal from the tachometer using a set of determined parameters. The determined parameters of the processing system are determined from the voltage levels of the variable voltage signal. An adaptive threshold is determined based on the difference between the minimum and maximum amplitude and their midpoint. In particular, a first variable threshold is set at a defined percentrage above the middle point between maximum and minimum, and a second variable threshold is set at a defined percentage below this middle point. A pulse shaped stepped output signal changes state at each crossing of the threshold. The ampltude of the input signal may be used to determine an approximate speed range which can be used for plausibility checks. |
