Bearing monitoring apparatus and method for monitoring bearing

A bearing monitoring apparatus comprising:

• a rolling bearing including
• an outer ring,
• an inner ring disposed coaxially with the outer ring, the inner ring being on an inner peripheral side of the outer ring,
• multiple rolling elements disposed between the outer ring and the inner ring, and
• a strain gauge configured to detect strain of the outer ring or the inner ring, the strain gauge including at least two resistors, and the resistors being arranged in a same direction as an arrangement direction of the rolling elements so as to correspond to spacing between rolling elements that are next to each other;
• a first circuit configured to generate a first distorted waveform based on an output of one resistor of the at least two resistors and to generate a second distorted waveform based on an output of another resistor of the at least two resistors;
• and
• a second circuit configured to:
• subtract the second distorted waveform from the first distorted waveform to generate a differential waveform;
• and
• compare the differential waveform against a reference value to detect a wear state of the rolling bearing.