ibrahim.abouelfettouh@LIGO.ORG - posted 16:12, Wednesday 10 July 2024 - last comment - 22:09, Wednesday 10 July 2024(79005)
BBSS Transfer Functions and Interpretation following Rebuild
Following TFs on alog 79004, we have been diagnosing the noisy TFs and have come to the simple realization that the DAC is not working and that we were simply not actuating due to a broken IOP Model DAC. All the noise was simply the natural dynamic modes as they were hanging in the clean room. We're getting in contact with the CDS team to fix the issue. Stay tuned.
Oli's Quick partial investigation: Oli plotted multiple channels that the excitation goes through to see if we could narrow down causes (L, T, V, and R). Here are the results with ss of the ndscopes to help compare.
L (January 5th, July 3rd)
The July measurement:
- No difference in excitation amplitude or measurement presets
- Excitation amplitude is almost 1/2 the January amplitude
- Same for coil driver INMONs
- OSEMs reading are close to January
- DAMP INMON is 1/2 the amplitude of January
T (January 5th, July 3rd)
The July measurement:
- No difference in excitation amplitude or measurement presets
- Amplitude read during excitation matches January measurement until OSEMs read the flag motion back in
V (January 5th, July 3rd)
The July measurement:
- Excitation amplitude - January: 1075, July: 1000, everything else the same
- excitation amplitude looks good, about the same size
- I have no idea what's going on with the OSEM readings. Seems like they get pushed away from the LED so more light shines through, and then are held there??
R (January 5th, July 3rd)
The July measurement:
- Excitation amplitude - January: 200, July: 175, everything else the same
- Same issue as V wrt OSEM readings
This showed that the issue was down the line, and gave the hint that the OSEMs may have not been reading to the IOP Model DAC.
Jeff Investigation
Jeff and I (Ibrahim) realized that the IOP Model DAC output on the screen was reading 0 despite actuations going down the chain to the user model output. We put in a DC offset and the chain remained at 0.
We then found that the GDS_TP IOP states were red in TIM, ADC, DAC, DK. We looked further and found that the FIFO status was also in the red (screenshots) and as such, we need to fix the IOP Model and re-take our TFs. Stay tuned.
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Viewing the January vs July attachments requires a caltech login, so here are the attachments for those without a caltech login:
L
T
V
R
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