Abstract: A method for determining imbalances in a mechanical system, such as a rotor, by detecting oscillations caused by the imbalances, selecting a useful signal having a particular amplitude and frequency from the detected signal, and filtering the useful signal so as to minimize errors contained in the useful signal, and providing a display which indicates the magnitude and phase displacement of the imbalance.

Abstract: A process and apparatus for measurement of nonuniformity of mass of a gyro rotor having a single bearing. The gyro rotor, which is mounted in a radially fixed and spherically yielding pivot, is rotated to a predetermined speed. The static imbalance of the rotating rotor is then determined by measuring the magnitude and angular position of excursion of the rotating rotor. A force couple acting on the gyro rotor and drift of mass of the gyro rotor are determined by sensing movement of a surface of the rotating rotor at two different times. Preferably, the determination of static imbalance, force couple, and drift are obtained in a single course of measurement. After the preceding have been measured, the components of a mass balancing operation for correcting the measured nonuniformities are determined.