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VIS (SR2)
fabian.arellano - 18:21 Saturday 20 June 2020 (14582) Print this report
IP-L open loop transfer function measurement.

This is the result of the measurement associated with entry 14581.

Summary

DC control OLTF: UGF: 8 mHz, phase: 83 degrees

AC control OLTF

  • UGF: 43 mHz, phase: -129 degrees,
  • UGF: 94 mHz, phase: 30 degrees,

Total DC + AC control OLTF

  • UGF: 6 mHz, phase: 83 degrees,
  • UGF: 47 mHz, phase: -139 degrees,
  • UGF: 90 mHz, phase: 29 degrees

Configuration and plots

  • Control off.
  • Suspension in NEUTRAL state.
  • I measured the OLTF for the DC and AC paths separately and added them afterwards.
  • See excitation input port and signal output port in the first figure.
  • See the other figures for the results.

Comments

The OLTF for the AC control path is consistent with what Foton gives with the IP-L transfer function that Enzo uploaded. See entry 14550. Besides the UGF (94 mHz versus 85 mHz) In the measured case the magnitude at 406 mHz is 0.27 whereas Foton gives 0.22

Images attached to this report
Comments to this report:
fabian.arellano - 17:47 Sunday 21 June 2020 (14585) Print this report

The files are in

/kagra/Dropbox/Subsystems/VIS/TypeBData/SR2/TF/Measurements/20200620/

fabian.arellano - 13:29 Monday 22 June 2020 (14589) Print this report

In case you don't see the figures attached please click here: 14589.

The measurement reported in the commented entry provides -OLTF rather than the OLTF directly.  Additionally, it's worth saying the measurement assumes the effect of ground motion to be negligibe compared with the effect of the white noise with which the system was actuated.

Results

After the sign correction the results are as follows:

DC control OLTF: UGF: 8 mHz, phase: -83 degrees

AC control OLTF

  • UGF: 43 mHz, phase: 129 degrees,
  • UGF: 94 mHz, phase: -30 degrees,

Total DC + AC control OLTF

  • UGF: 6 mHz, phase: -98 degrees,
  • UGF: 47 mHz, phase: 41 degrees,
  • UGF: 90 mHz, phase: -151 degrees

Commets

In the total OLTF:

  • The phase at 406 mHz is -220 degrees
  • The phase at 671.9 mHz the phase is -200 degrees.
Images attached to this comment
fabian.arellano - 12:40 Tuesday 23 June 2020 (14595) Print this report

Correction of the results reported in entry 14589.

In case you don't see the figures attached, please click here: 14595.

I found an error in my script that affected the phase in the plots of the DC OLTF and AC OLTF, but it didn't affect the phase of the total OLTF. After correcting it I did consistency checks and I report the correct result here.

The measurement reported in entry 14582 provides -OLTF rather than the OLTF directly.  Additionally, it's worth saying the measurement assumes the effect of ground motion to be negligibe compared with the effect of the white noise with which the system was actuated.

Results from OLTF

DC control OLTF: UGF: 8 mHz, phase: -97 degrees

AC control OLTF

  • UGF: 43 mHz, phase: 51 degrees,
  • UGF: 94 mHz, phase: -150 degrees,

Total DC + AC control OLTF

  • UGF: 6 mHz, phase: -98 degrees,
  • UGF: 47 mHz, phase: 41 degrees,
  • UGF: 90 mHz, phase: -151 degrees

Commets

From the fourth plot which shows the total OLTF with the phase unwrapped:

  • The phase at 406 mHz is -580 degrees.
  • The phase at 671.9 mHz the phase is -560 degrees.
Images attached to this comment
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