Abstract: An accelerometer mechanically attached to a machine senses the machine rotor's unbalance and outputs an electrical signal which is indicative of the magnitude and position of the rotor unbalance. A tachometer generator's rotor is mechanically coupled to the machine rotor and outputs an electrical signal delineating the speed and rotational position (with respect to time) of the rotor. By physically indexing one of the tachometer generator rotor poles (north or south) to an index/mark on the engine rotor, the position of the mark at any instant in time is determined. The physical location of the unbalance is obtained by determining the phase relationship of the unbalance signal to that of the tachometer generator signal. This is accomplished by obtaining simultaneous "snapshots" of the two signals employing multiplexing techniques to alternately sample each signal. The signal is then recorded and later reduced by ground equipment.

Abstract: An accelerometer senses a machine's vibration resulting from unbalance of its internal rotors and outputs an electrical signal which is then conditioned by means of an amplifier and uniform level filter. The resulting output signal has individual vibration (frequency) components which are adjusted to match the machine's specified vibration limit extending over each of the rotors' frequency range to achieve a uniform level. A storage oscilloscope is employed to display the conditioned signal.By utilizing the uniform level filter a normal operating band for the machine can be specified in terms of oscilloscope divisions regardless of the machine's operating frequencies. When a signal exceeds the specified band on the oscilloscope the rotor causing the excessive vibration may then be determined by analyzing the individual components. Utilizing relatively uncomplicated electronics, a limit exceedance warning may also be incorporated.