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Entry  Mon Aug 30 13:57:25 2010, Koji, Summary, PSL, PSL table vibrational performance after the upgrade PEM_100830_SPE.pdfPEM_100830.pdf
    Reply  Mon Aug 30 18:22:00 2010, rana, Summary, PSL, PSL Enclosure is UNSTABLE 
Message ID: 3487     Entry time: Mon Aug 30 13:57:25 2010     Reply to this: 3488
Author: Koji 
Type: Summary 
Category: PSL 
Subject: PSL table vibrational performance after the upgrade 

Jenne and Koji

Last week Jenne has put the accelerometers on and under the PSL table immediately after the plastic sheets were removed.

So I took the same measurement as I did on 9th Aug.

Here is the comparison of the vibrational performance of the table before and after the modification.

Basically the table is now stiffer and more damped than it was before.
We don't find any eminent structure below (at least) 70Hz.

This result is obtained despite elevating of the table.

1) Attachment 1

For the horizontal comparison (top),  it is clearly seen that the large resonant peak at 20Hz was eliminated.
At least the new resonances went up to 70-90Hz region. Y is basically equivalent to X.

For the vertical comparison (bottom), it is clearly seen that the resonant peaks at around 50 & 70Hz were eliminated. 
At least no new resonance is seen.

2) Attachment 2

All-in-one plot for the measurement --- spectra, coherences, transfer functions --- after the upgrade. I put the same plot for the one before the upgrade.

Attachment 1: PEM_100830_SPE.pdf  130 kB  | Hide | Hide all | Show all
Attachment 2: PEM_100830.pdf  1.410 MB  | Show | Hide all | Show all
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