I did the following:

• Noticed that the OMC rack's power has +-18V, but I had tested the HV driver with +-15V. Maybe fine, something to watch.
• Checked that nothing but the OMC driver board was in use on the OMC's Sorensen (the QPD whitening board in the OMC rack is not in use, and anyway is labeled +-15V), then turned down the rack voltage from 18 to 15V. Photos attached of AUX_OMC_S Sorensen bank.
• I hadn't used the alternative dither before. I started by driving the alternative dither with a 10Vpp sine wave at 1-10 Hz. I have both the DC and AC driver mons on a scope.
  • Initially, I only give it 10V at the HV. I don't see much, nor at 30V, while driving with 0-10V sine waves between 0.1-100Hz.
  • In my last log, I hadn't been using the alternative dither.
• Instead, I switch over to the main piezo drive, which is sent over DB9. Now I see the following on the AC/DC piezo mon channels:
  • Increasing the HV input (increasing in steps from 10-50V) yields 1V at the DC piezo mon for 50V at the HV input.
  • Driving under a few 100s of Hz results in no change to the AC dither mon. Driving <1Hz results in a small (~10% for a 10Vpp drive) at the HV. I didn't take a full transfer function, but it is the thing to do with cds.
  • Changing the drive amplitude changes the AC mon amplitude proportionally
  • At a few kHz, the 10Vpp drive saturates the AC mon.
  • Photos are in order:
    • 1Hz drive, visible on the DC mon channel in green
    • 1kHz drive 10Vpp, visible on the AC mon channel in violet
    • 1kHz drive 5Vpp
    • 5kHz drive 10Vpp, saturates the AC mon channel