Shaker Mounting and Alignment. Proper force excitation requires the thrust axis of the modal shaker to be aligned with the force sensor (or impedance head) mounted on the structure
under test. Failure to do so may result in unmeasured forces transmitted to the structure due to the side loading of the sensor and possible mechani- cal or electrical shaker damage due to forcing and rubbing of the armature coil. Alignment issues cause difficulty in any modal test. Care must be taken to provide the best alignment possible to attain the best pos- sible measurements.