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Entry  Tue Jan 6 03:09:17 2015, diego, Update, LSC, PRFPMI status & IFO status Lockloss_20150106_074552.pngLockloss_20150106_074552_zoom.png
    Reply  Tue Jan 6 03:13:09 2015, ericq, Update, LSC, PRFPMI status & IFO status Jan6lockloss1_zoom.pngJan6_asdcjump.png
    Reply  Wed Jan 7 03:04:13 2015, Jenne, Update, LSC, TRY (thorlabs pd) weird noise TRY_60Hz_peaks_5Jan2015.pdf
    Reply  Wed Jan 7 03:09:15 2015, Jenne, Update, LSC, PRFPMI status & IFO status 
Message ID: 10862     Entry time: Wed Jan 7 03:04:13 2015     In reply to: 10856
Author: Jenne 
Type: Update 
Category: LSC 
Subject: TRY (thorlabs pd) weird noise 

[Jenne, Diego, Rana]

This is a note about work done last night. 

We were starting to lock, and saw glitches in the Thorlabs TRY PD about once every 1/60th of a second.  It is not a sine wave, so it is not 60Hz line noise directly.  It looks like this:

TRY_60Hz_peaks_5Jan2015.pdf

Rana pointed out that this looks like it could be from a power supply that is converting AC to DC. 

We went down to the Yend, and noticed some weird symptoms.  So far, we do not know where the noise is coming from.  Rather, we are just using the QPD for locking.

* The noise comes and goes, particularly if someone is moving around at the end station.

* Moving the Thorlabs power supply farther from the HeNe power supply didn't do much.  Turning off and disconnecting the HeNe supply didn't make the noise go away, so we conclude that it is not the HeNe's fault.

* We suspected the loops of excess cable that were sitting on top of iscey, but moving the coils away from the computer did not make the noise go away.

* We removed a few disconnected BNC cables that were near or touching the end table, but that didn't fix things.

* We disconnected the PD's signal cable and pulled it out of the table enclosure, and then put it back.  Noise was gone when cable was disconnected (good), but it was back after plugging the cable back in.

* The noise still comes and goes, but we don't have to use the Thorlabs PD for locking, so we leave it for another day.

RXA: also moved the Thorlabs power supply to a different power strip and tried putting it closer/farther to the Uniblitz shutter controller. Another suspect is that its some PWM type noise from the doubler crystal temperature driver. Need to try turning off the heater and the Raspberry PI to if it effects the noise.

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