As reported in elog2281, the HAMAMATSU PSD electronic noise level is similar with DGS ADC noise. In this entry, I report a futher investigation of them.

1. I had a closer look into these two noise spectrum. As shown in the attached figure 1 (RED is elec noise, BLUE is ADC noise, GREEN/BROWN are integrated noise), elec noise is a bit higher than ADC noise but not a factor of  2. Therefore, to investigate further the electronic noise, we should amplify signal from PSD before it goes inside DGS system.

2. Before amplification of PSD individual signal, I checked the time series of individual signal from PSD. This is shown in the attached figures 2. We could see that it has very large noise. Therefore, it is very diffcult to amplify such large noisy signal. Indead, I found SR560 could only give a factor of 2 amplification for it before saturation. But the good thing is that, after the combination inside DGS, this noise is cancelled and resulted in a clean pitch/yaw electronic noise.

So if we really want to check better the electronic noise, we should combine PSD individual signal before they go inside DGS system.