Craig, Rich, Peter, Stefan,

We tried to measure and fine-tune the DCPD whitening filter compensation. so we took the following measurments:

a) Analog transfer function on the floor for PDA & PDB; FM1FM2FM3 all off and FM1FM2FM3 all on (run configuration). (That's 4 measurements total.) That data is still on disk and Rich will post it.

b)  Driving both DCPDs with noise, measure the PDA/PDB transfer function. This is done with FM1&FM2 on PDA and FM1 on PDB, normalized by  FM1 on PDA and FM1 on PDB to take out other systematics.

Measurement b) was performed with a variety of noise sources:

i) IFO on AS_RF45, with additional 100Hz-1kHz frequency noise injection. (IFO)
ii) White noise drive (10Vpkk) (Orig white)
iii) Same white noise, but FM6 filters in PDA and PDB off (White 2). Note that changed the transfer function at the 1e-3 level compared with ii) - consistent with T990013-B (dtt documentation)
iv) Same white noise, but now filtered by SR560 with 2 poles at 100Hz (Pink)
v) White noise at half the level (5Vpkk) (White 3)
vi) Same as white 3, but with 2 poles at 100Hz in the digital system (W3 Dig Poles)
vii) Same as white 3, but additional 2V offset (~13000cts at IN1) (W3 offset)
viii) Simple model z59.8265:p60.174,120k

Note that at 100Hz the transfer function is changing by as much as 0.3dB (3.5%) with drive level..THis is much bigger than the expected dtt error, so we conclude it is real, We will deal with the implications for calibration tomorrow.