Abstract: The vibration of a moving device which has repetitive movements, for instance a rotary compressor, are sensed at the outer case and analyzed in real time in both the time and frequency plane. For the time analysis the envelope of the signal is generated; for the frequency analysis a fast Fourier transform is performed and separate power spectra for fractions of a revolution are produced. The signatures are compared with those of an acceptable device to identify rejects and abnormalities at a particular position of a moving part.

Abstract: An acoustic diagnostic system for detecting misalignment of switch blade contacts in power distribution systems is disclosed. In accordance with one embodiment of the present invention, the high frequency component of the acoustic signal generated by the make and break of electrical contacts in high energy power distribution equipment is filtered and demodulated to produce a waveform from which significant timing information is provided. A method for producing these waveforms is also disclosed.

Abstract: To locate a corona fault in a transformer or other encased electrical apparatus by determining the propagation time for acoustic noise generated by a corona discharge, the electrical corona signal is gated and level-detected during an interval which is adjustable as to delay and length to thereby generate a timing reference to initiate acoustic signal averaging. The corona pulse can be found that results in an optimum signal-to-noise ratio in the acoustic signal being averaged, as is needed with limited test data in a noisy or reverberant acoustic environment. Also, multiple corona sources can be located.