PURPOSE:To achieve a reduction in test preparation time and a higher safety of a test along with a higher performance of the apparatus, by mounting a weight on one of right and left arms in such a manner as to be movable radially. CONSTITUTION:A weight 20 is mounted on one of right and left arms 2 in such a manner as to be movable radially and a actuator 21 is moved to adjust a balance between centrifugal forces F1 and F2 generated during the turning of the weight 20. In the implementation of a test, theta1 theta2 90 deg. is set and the radius r3 of rotation of the weight 20 is controlled with the actuator 21 to establish a horizontal balance. If so, there is no bending moment generated in a drive shaft 1 to cause no whirling. Hence, as the oscillation of the arms 2 reaches an allowable upper limit value, a signal is generated from an oscillation range detection sensor 22 to be compared with a signal from a rotation reference position detecting sensor 23 and a control circuit judges to which side the oscillation occurs and which of a sample box 4 containing a test object 14 and the weight 20 is large in centrifugal force. This allows the maintaining of an oscillation range below the allowable upper limit through a changeover valve 17.
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