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fabian.arellano - 18:46, Wednesday 25 September 2019 (10699)Get code to link to this report
Input Y and End Y coil driver harmonics.

With Aso-san, Lucia, Yamamoto-san, Okutomi-san, Nakano-kun

Entry  10687 reports the presence of non-linear components in the output of End Y horizontal marionette super high power coil driver. Today we aimed to identify the impact of the non-linearity by analyzing the behaiviour of a healthy coil driver, namely Input Y horizontal marionette coil driver.

  • We connected the monitor of the coil driver into the digital system and measured the amplitude spectral density (ASD) shown in the first figure when actuating MN-L with a signal at 0.2 Hz and 10,000 counts in amplitude. The harmoics are clearly visible and they are about 4 orders of magnitude smaller then the excitation at 0.2 Hz.
  • Then we connected the output from the anti-imaging filter (before the coil driver) into the digital system and measured the ASD again. As shown in the second picture the harmonics are still there.
  • Later we connected the output from the ADC (before the anti-imaging filter) directly into the digital system and measured the ASD again. As shown in the third picture the peaks are still there.
  • We left the coil driver monitor connected in cae we want to check it again soon. See the screenshot for channel names and location of the measured data.

In a healthy systyem the amplitude of the harmonic peaks are 10,000 smaller than that of the excitation. These measurements suggest this amount  of non-linearity is not the origin of the problem reported in entry  10673, which affects the End Y marionette.

Later we went to the End Y. Over there

  • We connected the coil driver monitor to the digital system. (Nakano-kun changed the channels used for monitoring to DAQ channels.)
  • We injected a signal in MN-L at 0.2 Hz with amplitude of 10,000 counts. We didn't see the troublesome non-linearity (so-called kick in entry 10673).
  • We changed the coil driver with a normal high power coil driver and adjusted the output gain in software accordingly with a factor of 2. (Only in H1 and H2 coil channel.)
  • We looked for the non-linearity again but we didn't find it. See the time series in the last picture.
Images attached to this report
10699_20190925114551_coildrivout.png 10699_20190925114555_aioutput.png 10699_20190925114602_dacout.png 10699_20190925114608_etmyoldcoildrive.png
Comments related to this report
takafumi.ushiba - 18:57, Wednesday 25 September 2019 (10701)

After their work, transfer function from MN yaw excitation to MN OpLev yaw signal was measured.
Attached is a measured result compaired with the transfer function on 19.
It seems fine.