Figure 1 show the spectra of GAS filter LVDTs and BFV of ITMX and ETMX.
All ITMX GAS LVDTs have 10 times larger noise at high frequencies.
During the health check, I found the ITMX GAS LVDT spectra are much higher than ETMX's.
According to the original post, this phenomena was observed in early November but probably forgot to fix them.
I asked Takahashi-san to change the LVDT driver cards and check if the noise will decrease or not.
[Takahashi, Sato]
To investigate the noisy LVDT signals, we replaced the LVDT card for GAS filters (F1, F2, F3, BF). The modified card showed the noise floor higher than the original card's one. The phase and gain of the modified card have not been adjusted. In another case, the main (interface) card had a noisy output. We will try to replace the main card as well.
[Takahashi, Sato]
We replaced the main card in the LVDT driver for the GAS filters (F1, F2, F3, BF) and the IP (F0, IP). The spectra were improved! The noise level was reduced very much. The F0 spectrum was also improved. This means that both outputs for the GASF and the IP were noisy in the original card.
