The APS Dynamics Model 300 Portable Shaker-Amplifier shown in the adjacent picture was used to excite the hard disk drive during a recent modal survey. The disk drive was suspended with rubber bands.  A burst random signal generated by the Hewlett Packard 35670A was fed to the Model 300 amplifier.  The amplified signal drove the shaker head.

A PCB Piezotronics load cell (not in view) attached to a flexible stinger rod was used to sense the input force, the disk drive response was measured with a tri-axial PCB Piezotronics accelerometer (not shown).  The disk drive frequency response [i.e., the ratio of the accelerometer response/output divided by the load cell signal/input] was calculated with the Hewlett Packard 35670A.

The frequency response functions were imported to a modal package where the modal parameters were calculated (damped natural frequencies, damping factors and mode shapes).