Just FYI.
Even without ISS, during O1 the 1st loop diodes didn't rail, but they do now. The power on these diodes seems to be the same as before (I assume Peter and Jason adjusted them).
Attached left is the trend of the past 26 hours. ISS first loop was on at first, but is off right now. You can see that the first loop diodes seem to be railing without ISS.
Attached right show the same channels, but from O1 when ISS first loop was off (seems to be related to ISS investigation in alog 24171).
If you compare the DC level of PDA and PDB from O1 against the recent trend when ISS was on, it seems like the DC power on the diodes are the same as before. This is not a digital filter issue, there's no digital filter on these channels except a calibration factor, and the calibration factor didn't change in the filter file. Dewhite is applied after PDA and PDB output in PDA_REL and PDB_REL channels.
It should be noted, and it is my understanding, that the DC value as shown on the MEDM screen is not the actual DC value output by the PD; it is calculated based on the AC value. There are connections for the DC, but to my knowledge the actual measured DC values of the ISS PDA and PDB are not read into EPICS at all (I could be wrong on this, but this is how it was explained to me). When we set the DC value while in the enclosure we use a multimeter and measure the DC value directly off of the PD, and adjust it to ~10V using a HWP at the input to the ISS box. The last time we set the DC value it was set to ~9.7V on PDA.
To clear some confusion. Whitened output of PDA and PDB ("filt" output from ISS BOX) are whitened but DC-coupled.
PDA and PDB whitened output are measured by ADC and become H1:PSL-ISS_PDA and H1:PSL-ISS_PDB, which are plotted and reported in my entry. DC values of these are really DC values, though there is a factor of about 0.45 0.2 whitening "gain" in the ISS box.
The only channels I know of on the PSL_ISS MEDM screen that are supposed to have finite DC values despite being calculated from AC-coupled channels are band-limited linear spectral density (LSD) channels H1:PSL-ISS_PDA_LSD and H1:PSL-ISS_PDB_LSD.
Unfortunately PSL_ISS MEDM screen seems to have some mislabeling and this might have made people confused. RIN outputs (H1:PSL-ISS_PDA_REL_OUTPUT and PDB) are labeled "lsd" while band limited LSD (H1:PSL-ISS_PDA_LSD and PDB) are labeled "relative".
Fixed the MEDM.
"lsd" labels are now "ASD" for both PDA and PDB. Two numbers in each red circle were swapped so now "ASD" is LSD channel and "Relative" is REL channel.
DC is DC, AC is AC, "Relative" is AC.
