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). |