peter.king@LIGO.ORG - posted 12:02, Wednesday 11 October 2017 - last comment - 16:58, Wednesday 11 October 2017(38990)
Noise eater
There was some ambiguity as to whether the NPRO noise eater was on or off because the MEDM screen
did not change.
Attached is a plot of the NPRO output as seen by the photodetector inside the front end laser
with the noise eater toggled on and off. Clearly the switch on the power supply works. However
the status indicator did not change. The output voltage of the photodetector was 0.210 V and the
number of counts on the MEDM screen was ~ -335. Blocking the light to the photodiode resulted in
the status indicator changing and an increase in the number of counts to ~ -5000. We know that
the change in status occurs around ~ -1792 counts.
I do not recall when this problem first manifested itself.
Images attached to this report
Comments related to this report
From the trend data, it looks like the noise eater signal started misbehaving about a week ago. The photodetector monitoring the output power of the NPRO seems to be still working. I would be inclined to check the field box that the H1:PSL-MIS_NPRO_RRO_OUTPUT is attached too, as there maybe a large DC offset in that monitor signal's output.