Sheila, Terra, Jeff K, Patrick, Nutsinee
Tonight we continued with the PRMI locking difficulties of yesterday. Nutsinee managed to lock PRMI by lowering the MICH gain and commenting the boost and offloading out of the guardian.
Patrick tracked down some differences between the "good" PRMI time that Jenne mentioned (Oct 17 16:03 UTC) and now, there was a filter missing in the BS top mass offloading, and two whtening stages (with the anti whitening) were engaged in the middle of the lock yesterday afternoon. We don't know why this happened, but just undoing it actually makes it impossible to lock at all.
To match the PRCL loop shape to a reference, I had to add 6 db of gain (PRCL digital gain of 16 rather than 8). However it looks like we still missing some kind of boost in PRCL (1st screenshot). The second screenshot shows the MICH loop measured today on the left, before and after the PRCL fix, and an old measurement on the left.
We have commented out the boost and offloading of MICH in the guardian for PRMI, and nutsinee created new prmi_mich_gain_als and prmi_prcl_gain_als parameters in lscparams, and we have set them to 0.7 and 16 for now, although the nominal values should be 1.4 and 8. You will have to reduce the MICH gain by hand to get it lock.
Could who ever did some measurements that required changing the REFLAIR whitnening gain triple check that whatever they did is not causing us problems in the morning?
I logged in and checked the Beckhoff machines for errors. All of the terminals are in OP. There is a CRC on h1ecatc1 EndXLink R5_6 (not sure what this means). The only other thing I noticed is that the Send Frames diagnostic is very high and increasing on all three machines (also not sure what this means). Attached is a screenshot of h1ecatc1.
Jim W, Kiwamu
As Sheila suspected, the difficulty turned out to be due to wrong whitening settings on REFLAIR RF45 which we had changed on this past Monday during the frequency noise study (30610). We found it having two whitening stages engaged with a gain of 12 dB which should have been no whitening gains with 0 dB according to trend. So we set them back to no whitening stages with 0 dB gain. This apparently improved the situation -- we are now able to lock DRMI reliably and proceed with the rest of full lock sequence.
The SDF is updated accordingly.