Then, I accepted the SDFs.
Please check the following figures.
Then I accepted the SDF.
I measured the transfer function. Please see Fig1 and refer to the diaggui file "/users/sugiyama/dropbox/Log/210825/etmx_fldaccservo_tf.xml".
The red line is the transfer function of H1, the blue is H2 and the green is H3. The dashed line is the transfer functions of H1, H2, and H3 without additional weight.
As you can see, the resonant frequency of all FP is around 0.2Hz.
We check the transfer function of the new accelerometers which will be installed on IP of IX.
·H3
H3 has the problem.
We can't actuate H3 because the number of turns of its coil is very small.
So, we replace the accelerometer. We tune in later.
·H1, H2
We measure the transfer function. Please see Fig1 and diaggui file "/users/sugiyama/dropbox/Log/210728/itmx_fldaccservo_tf.xml".
The red line is the transfer function of H1 and the blue is H2. Their resonant frequency is around 0.2Hz which is the target.
After that, we insert a simple servo filter and measure the spectrum.
Please see Fig2 and diaggui file "/users/sugiyama/dropbox/Log/210728/itmx_fldaccservo_spectrum.xml".
The red line is the spectrum of H1, the blue is H2, and black is the spectrum of geophone installed on the near ground.
As you can see, H1 and H2 are capable of measuring microseism. So, the accelerometer can use for IP damping.
·Next work
We will optimize the servo filter, and tune H3.
We tuned the three accelerometers.
2021.5.25
・H2
Takahashi-san attached some weights to H2, one 3.0g, one 6.0g, three 31.0g, and two 34.6g weights.
I measured the transfer function. Please see Fig1 and refer to the diaggui file "/users/sugiyama/dropbox/Log/210525/itmx.fldaccservo2".
The red line is the transfer function with the resonant frequency tuned to 0.2Hz.
・H3
Takahashi-san attached some weights to H2, one 6.0g, two 12.0g, and one 34.6g weight.
I measured the transfer function. Please see Fig2 and refer to the diaggui file "/users/sugiyama/dropbox/Log/210525/itmx.fldaccservo3".
The red line is the transfer function with the resonant frequency tuned to 0.2Hz.
Coherence in low frequency is bad. So, we tuned H3 with prediction.
2021.5.26
・H1
H1 was tuned before, but its transfer function is higher than 0.2Hz. So, We tune it again and measure its transfer function.
Please see Fig3 and refer to the diaggui file "/users/sugiyama/dropbox/Log/210526/itmx.fldaccservo1".
The red line is the transfer function with the resonant frequency tuned to 0.2Hz.
Finally, H1 was attached one 3.0g, two 12.0g, three 31.0g, and one 34.6g weight.
・Three accelerometers
After we tuned three accelerometers, three accelerometers were placed side by side and covered with a container.
Then I measure the transfer function of the three accelerometers at the same time.
Please see Fig4 and refer to the diaggui file "/users/sugiyama/dropbox/Log/210526/itmx.fldaccservo.all.tf".
The red line is H1's transfer function, the blue line is H2's transfer function, the green line is H3's transfer function.
H3's coherence is better than yesterday's. So, we tuned all accelerometer's transfer functions to 0.2Hz.
・Problem
I measure the spectrum of H1, H2, and H3.
Please see Fig5 and refer to the diaggui file "/users/sugiyama/dropbox/Log/210526/itmx.fldaccservo.all.sp".
H2's spectrum has two peaks. The left peak is almost 0.2Hz. But, H2 has one more peak. This is the problem.
We will check the source of the problem.
See the figure below.
The red line shows the transferfunction of the accelerometer connected to LVDT distributer. The blue line shows the transferfunction of the accelerometer connected to IP system. As you can see, the peaks of the two transferfunctions are about the same. However, the phase of the red line is π out of phase with the blue line. I think I have connected the wiring somewhere in reverse, but that is not a serious problem.
(1)Install new LVDT distributer(S1503682) at 23 in IXV1 rack.
(2)Connect the accelerometer to ch0 of this LVDT distributer.
(3)Connect the LVDT driver(S1403051) to the LVDT distributer. Sec to LVDT-IN. Pri to LVDT-OUT. This LVDT driver is connected to IN 21-24 of AA(S1707018) from Test In.
(4)Connect the HPCD(S1604827) to the LVDT distributer. Coil Out to ACT. This HPCD is connected to OUT 5-8 of AI(S1807861) from Main.
The picture below shows the wiring diagram.
We check the transferfunction of the accelerometer.
