NAOJ GW Elog Logbook 3.2
Displaying report 1-1 of 1.
NaokiAritomi - 10:40, Sunday 02 August 2020 (2136)
WFS2_Q3 is not working
[Aritomi, Matteo]
After we locked both of galvo loops, we checked WFS2 signals.
We found that WFS2_Q3 had large offset (~4000) compared with others(<10). Even when we put 50 Ohm to DGS input of WFS2_Q3, WFS2_Q3 is still very large. So this problem seems to come from DGS.
To avoid using WFS2 Q phase signals, we injected 12Hz pitch line in input mirror and tried to minimize the 12Hz peak in WFS2_Q1 (maximize WFS2_I1) by changing the LO demodulation phase from DDS. The measured result is as follows.
| DDS demodulation phase (deg) | WFS2_I1 | WFS2_Q1 |
| 70 | 0.031 | 0.008 |
| 80 | 0.034 | 0.010 |
| 90 | 0.047 | 0.008 |
| 95 | 0.040 | 0.010 |
| 100 | 0.012 | |
| 110 | 0.019 |
The original DDS demodulation phase is 90 deg and it is already good demodulation phase. So as long as we use WFS2 I phase, this will not be a problem.
The measured result is as follows.
As reported in entry #2117, the large offset in WFS2_Q3 is due to a broken channel (n°14) in the Anti-Aliasing board (AA1). It can be solved by using some spare AA channels but so far we considered that we won't use Q signal for AA. So we decided to wait untill the BNCtoDsub issue (that is likely to cause this kind of problem) is solved.