Speed measuring apparatus for indicating percentage of nominal full speed, acceleration and deceleration

摘要

A speed measuring apparatus is provided for indicating a percentage of nominal full speed RPM of a jet engine and also for indicating time required for accelerating and decelerating the engine. A generator output is converted to a square wave and a time interval measurement is made between zero crossings of the square wave. The square wave controls the starting and stopping of a time period counter and measured time is converted to percent RPM which is displayed on a digital incandescent display. Similar time periods are measured when the engine is advanced from idle to full power, and also when the engine is retarded from full power to idle.