TJ, Betsy and Rahul

Today morning at 8.10 am, we started performing the charge measurements on the ETMX and ETMY, since the interferometer was unlocked. Initially we did 5 measurements, however Jeff Kissel found out that the DAC was constantly being saturated (alog 46621). He fixed it by reducing the quadrant drive amplitude from 124k to 110k, with a 20 bit DAC (former was 18 bit DAC). Hence, we had to redo the measurements again for the ETMX. Due to paucity of time (priority was to lock the interferometer in the morning) we had to truncate the measurements and we could get only 3 data against 5. 
Later we analyzed the data on MATLAB, and the long term trends are shown on the plots attached. For the ETMX the effective bias is at 10 V, which looks very good. Comparing this to the data which we took on the 22 Jan (Tuesday) (alog 46582), which looked very bad (effective bias -90V, STDEV +-70V). We believe that there is some error on the measurements from 22 Jan, with very large standard deviations and thus have deleted this from our latest plot. For the ETMY the effective bias is almost at zero, which is excellent.