J. Kissel, R. Kumar, T. Shaffer, B. Weaver

Rahul and TJ were running another round of charge measurements this morning because Tuesday's results didn't come out well. Upon getting in, and happened to have had the ETMX screen open, I notice that the charge measurement's drive on each quadrant was constantly saturating the DAC. As the Dothraki say, "it is known" that (for an as-yet-unknown reason) our new 20-bit DAC on ETMX L3 stage (see LHO:44905) -- even though it's billed to have the usual 10 V range -- has less range before front-end code complains of saturation**. Thus the charge scripts, which request to drive the full range (well, 124k ct of the theoretical +/-131k ct) of the 18-bt DAC, were now saturating new DAC. ***

As such, I've reduced the drive amplitude to the quadrants to 110k in the charge script for ETMX:
    /ligo/svncommon/SusSVN/sus/trunk/QUAD/Common/Scripts/ESD_Night_ETMX.py

The charge team will post an aLOG of the (hopefully improved) results in a bit.

** This is why our ETMX ESD Bias Voltage has been set to 9.3 V_DAC (372 V_DAC) instead of the O2 level of 9.5 V_DAC (380 V_ESD). I found this out while recovering from when the DAC was swapped from 18 to 20 bit DAC (LHO:44905), and failed to report it. Further, after calling Joe Betz, he confirmed that LLO had to do the same thing (and also failed to report it). Think it's time to report it! I'll create an FRS Ticket shortly.

*** You would think 124k would only be 23% of the +/- 2^19 ct range of the 20-bit DAC, but no --more details--blah-blah-- we compensate for have a 20-bit DAC with a gain of 4 down-stream of where the charge measurement script drives [see LHO:44905], so the drive calibration is still in 18-bit DAC units.