Abstract: An abnormal vibration monitor is used for a monitor by detecting the abnormal vibration of a rotary device placed in an explosive atmosphere by using a plurality of piezo-pick-ups. In the monitor, many signal wires and power source wires for devices are placed in an explosive atmosphere whereby there is a possibility of an explosion. In order to prevent the explosion, pre-amplifiers for detection which are respectively connected to the piezo-pick-ups and scanners for scanning the pre-amplifiers and power sources are contained in one antiexplosion casing and the casing is placed in the explosive atmosphere and the parts in the casing are connected by only small number of cables to the monitor placed in an nonexplosive atmosphere. The piezo-pick-ups are respectively fixed to parts for vibration out of the casing to give high detection accuracy.

Abstract: A bearing failure judging apparatus correctly judges the type of the cause of a failure of a bearing by synthetically judging many factors found in a vibrating waveform of a vibration produced when a failure takes place in the bearing i.e. various features of the time-waveform; a localization of the amplitudes of the time-waveform, the periods of pulsating waves, a degree of the acuteness of the waveform depicted by its envelope, the presence or absence of the proper peak value in the frequency spectra, and a change of the waveform after a given time.

Abstract: A system for detecting whether a machine is in the normal or abnormal state by comparing detected values of waveforms of signals such as vibration generated from the machine with a set value a plurality of times to indicate failure of the machine when the detected values reach the set value a predetermined number of times.