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Message ID: 181     Entry time: Sun Aug 4 16:36:07 2019
Author: Marie K. 
Type: Summary 
Category: BS BRDs 
Subject: Summary of BS measurements after retuning 

Andy retuned BRD1_v4 and BRD3_v4 after they had been left alone for a week in the lab. The tuning is described here: alog 177. It is better than 0.4% for all modes of the BRDs. I reinstalled them on BS right afterwards and took measurements of the bounce and roll modes over the following days:

We can see (figure 1) that the resonances are drifting. The BS bounce mode is 16.69 Hz without BRDs, so it is probably B2 here with the added mass.

Bounce

B1 Freq. [Hz]

Q1 (from 3dB width) B2 Freq. [Hz] Q2 (from 3dB width) BRD tuning Measured range  Nb points Drive [V] Filename Comments
Measurement B12 16.550 108 16.747 172 - 16 - 17 600 1 srs0034.txt BRD1_v4 & BRD3_v4
Measurement B13 16.555 153 16.761 232 - 16 - 17 600 1 srs0041.txt BRD1_v4 & BRD3_v4
Measurement B14 16.560 139 16.754 227 - 16.4 - 17 600 1 srs0042.txt BRD1_v4 & BRD3_v4

 

The roll mode also experiences drifts, but to a lesser extent. The BS roll mode is 24.34 Hz without the BRDs. It is probably R2 here with the added mass.

Roll

R1 Freq. [Hz]

Q1 (from 3dB width) R2 Freq. [Hz] Q2 (from 3dB width) BRD tuning Measured range  Nb points Drive [V] Filename Comments
Measurement R13 24.034 126 24.507 160 - 24 - 25 600 1 srs0033.txt BRD1_v4 & BRD3_v4
Measurement R14 24.049 138 24.526 187 - 23.5 - 25.5 500 1 srs0039.txt BRD1_v4 & BRD3_v4
Measurement R15 24.051 139 24.528 195 - 23.5 - 25.5 600 1 srs0040.txt BRD1_v4 & BRD3_v4

 

Unfortunately, some of the measurements are not readable. I will retry the conversion from .78D to .txt. Files I have to mention that saving the data from the spectrum analyzer is unreliable at times, I already lost few hours of measurements because the files were not saved correctly into .78D in the first place (.78D files were empty).

Attachment 1: B12_B14.png  190 kB  Uploaded Sun Aug 4 19:47:02 2019  | Hide | Hide all
B12_B14.png
Attachment 2: R13_R15.png  193 kB  Uploaded Sun Aug 4 20:01:51 2019  | Hide | Hide all
R13_R15.png
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