5. A METHOD OF CHECKING A VIBRATION ANALYZER ADAPTED TO RECEIVE SIGNALS FROM A VIBRATION PICKUP HAVING TWO SETS OF COILS, EACH SET OF COILS CONSISTING OF TWO SERIES CONNECTED COMPONENT COILS OPPOSITELY WOUND RELATIVE TO ONE ANOTHER AND TWO MAGNETS AXIALLY SHIFTABLE RELATIVE TO SAID COILS, EACH OF SAID MAGNETS BEING MAGNETIZED IN A DIRECTION PARALLEL TO THEIR AXIS OF MOVEMENT, SAID VIBRATION ANALYZER BEING EFFECTIVE TO ANALYZE UNBALANCE FORCES OF A DEVICE HAVING A ROTATING MEMBER ROTATED WITHIN A PREDETERMINED SPEED RANGE, SAID METHOD COMPRISING THE STEPS OF REMOVING THE VIBRATION PICKUP FROM ENGAGEMENT WITH SAID APPARATUS BEING TESTED, CONNECTING ONE SET OF COILS OF SAID PICKUP TO AN OSCILLATOR HAVING AN OUTPUT SIGNAL WITH A FREQUENCY WITHIN THE FREQUENCY RANGE OF THE APPARATUS BEING TESTED, APPLYING A VELOCITY DEPENDENT SIGNAL FROM A SECOND SET OF COILS OF SAID PICKUP TO SAID ANALYZER, AND COMPARING SAID ANALYZER READINGS WITH PREVIOUSLY OBSERVED READINGS.