PURPOSE: To observe an abrasion condition of a bearing without stopping a pump to dismantle permitting an eddy current vibrometer provided with a porcelain protection cover on a detecting head to provide for a pump case by penetrating through the motor casing.

CONSTITUTION: Eddy current vibrometers 12A, 12B, 12C, provided with a porcelain protection cover 16A on the detecting head, is provided for the pump case by penetrating through the motor casing 1. Regarding the eddy current vibrometer, the electric induction of coil 15A is variable according to the distance between coil 15A and axis 4 where an eddy current is flowing by a magnetic flux penetrating through the porcelain cover 16A. Accordingly, the abrasion condition of the bearing 8 may be observed by the distance fluctuation between coil 15A and axis 4, namely deflection of axis 4, by measuring the variation of current. Similarly, the abrasion condition of the bearings 9, 10A, 10B may be observed with the eddy current vibrometers 12B, 12C without stopping a pump to dismantle.