There is disclosed a device for detecting damage on rotators or rotary bodies such as for example ball bearings having rolling elements. A mechanical vibration or sound produced periodically due to damage on the rotator when it is rotated is converted into an electric signal. In order to identify such damage on the rotator by utilizing the periodic characteristic of said electric signal, a peak detector is provided for detecting a peak value of said electric signal, holding the detected peak value for a fixed period, and being reset to a base level by a reset signal.
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