[Takahashi, Washimi]
We located a laser displacement sensor below the OMC suspension.
The temporal channel is
K1:PEM-PORTABLE_SR_BOOTH_SR_BNC2_OUT_DQ
(used for the OMM PDA before)
[R.Takahashi, Washimi]
Today we tried to measre the resonant drequencies and damping time of the OMC suspension.
At first, we tapped a blade spring by watching the diaggui spectrum with exponential mode.
We couldn't see any excess peaks around 90Hz (blade internal mode) and only around 2Hz was excited (wire pendulum mode or blade spring mode).
Fig.2 is the signal plotted offline.
After that, we measured the damping time by softly tapping the OMC breadboard with a piece of white tape (Fig.3) from 3 directions (Fig.4).
The damping time was about 10s or so (Fig.5).
When we tapped the frame that holds the OMC suspension, around 74 Hz was excited.
I evaluated the damping time (X-direction tapping), by fitting the data with a simple sine*exponential function using scipy.optimize.curve_fit .
The result was τ = 4~5 seconds.
The Y/Z-direction tapping data show beating waveforms. So, a more complicated analysis is necessary.
