Dan, Evan
We measured the dark noise of the OMC DCPDs with the IMC unlocked and MC2 misaligned. (We also trimmed the dark offsets.)
The attached xml file & plot has measurements of OMC-DCPD_{A,B}_IN1 and _OUT with zero, one, and two stages of analog whitening enabled (and the corresponding digitial dewhite filters). The y-axis units are in cts/rt[Hz] for the IN1 channels, mA/rt[Hz] for the OUT channels.
With zero whitening (the case for the locks last night), the ADC noise is about 7x10^-3 cts/rt[Hz] at IN1. Last night our noise was about 10x larger than this (see upper left plot here).
Some notes about the conversion of the DCPD signals from counts to milliamps in the DCPD filter banks:
- FM4: flat gain of 1/1638
- FM5: dc gain of 0.005, two poles at about 7 Hz, two zeros at about 81 Hz, then two pairs of zeros and poles around 740 Hz [refer to T1300552]
- FM7: flat gain of 0.25.
In the noise budget, we have
- Preamp: dc transimpedance of 400 V/A, two poles at 7.3 Hz, two zeros at 79 Hz, single-to-differential gain of 2 V/V.
- Whitening block: no whitening
- AA block: flat gain of 1 V/V up to 10 kHz
- ADC gain of 1638 ct/V.
These agree with each other.