Longitudinal Mode frequency @ 420 Hz

Monday, January 28, 2013

Tests of resonant frequency specifically for longitudinal mode done on PMC because the piezo will only affect this length.  Originally the PMC spacer was constrained in motion by clamps on the PMC base, as shown below.

 Data was taken with an oscilloscope and laser vibrometer - the B&K system was not functioning correctly - and the PMC spacer was excited by hitting it with a marker.  The PMC was hit near the endcap, along the long axis of the PMC, as shown in the below image.

The results in the time domain are shown below and indicate a resonant frequency of 450 Hz.  A next step is to fit this data to a decaying sine wave.

When the above clamps were loosened to allow for more motion, the frequency dropped to closer to 350 Hz.