= PR2 =

With Fabian, log on May 22th 2019.

-- From klog#8149, it was known that BF-LVDT-V2 signal had not been available since somewhere in the LVDT board (especially for the channel) looked broken.
  -- Then it was found that the circuit for the channel, BF-LVDT-V2, was sometimes actully working properly but sometimes not, depending on tension of one or two cables connection (which was at front pannel of BF-V LVDT driver, labeled BF-V-OUT).
  -- This was not improved even though the cables were replaced to new ones. However, this issue went away when another LVDT board was used (which was already installed one and which had not been used so far).
    -- Then the not-used LVDT driver in the chassis of GAS-filters (The right one from the) was installed as the BF-V LVDT driver.
    -- The phase was tuned so that abs(signal) became the maximum, and the gain was tuned so that the transfer function from BF-Vexc to BF-V1/V2/V3 had same amplitude before/after the replacing work.
    -- Also the amplitude of the function generator for PR2 suspension was somwhow set to 5Vpp, even though the installation work seemed to be done with 6Vpp.
    -- I have changed the amplitude of the function generatpor to 6Vpp, and changed the dc-control offset and feedback loop gains (only for GAS filters) accordingly. It was confirmed that the guardian worked properly.
  -- After this tuning, klog#8952 was conducted.