SPEED MEASUREMENT SYSTEM

A speed measurement system including a magnetic pickup positioned in proximate relation to a driven element of a gas turbine engine having a plurality of discontinuities therein. The pickup providing a pulse per every discontinuity and thus a multiplicity of pulses for every revolution of the driven element. Conditioning circuitry connected to the pickup for generating a strobe pulse signal for every discontinuity. Interval measuring circuitry receiving interval signals asynchronous to the strobe pulses of a predetermined period which are to form a measurement period which is exactly related to a count of the strobe pulses over a measurement period. Additionally included is circuitry used to lengthen the measurement period up to a maximum of N intervals for increasing the low frequency response of the system.