40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  PSL  Not logged in ELOG logo
Entry  Thu Sep 5 19:32:02 2019, anchal, DailyProgress, PMC, North PMC might be cause of 500Hz bump BN_NPMCErr_CrossSpec.pdf
    Reply  Mon Sep 9 16:31:34 2019, anchal, DailyProgress, PMC, North PMC open loop investigation NPMC_openInvestifation.pdf
       Reply  Tue Sep 10 17:13:51 2019, anchal, DailyProgress, PMC, North PMC Servo Card Upgraded 
Message ID: 2417     Entry time: Thu Sep 5 19:32:02 2019     Reply to this: 2420
Author: anchal 
Type: DailyProgress 
Category: PMC 
Subject: North PMC might be cause of 500Hz bump 

I was looking at the error signals of PMC servo and found some systematic oscillations in NPMC error signal at around 500 Hz.

So, I connected back the beatnote to the Marconi PLL and used the error signal from there to measure beatnote - NPMC error signal cross-spectrum. Here, the channel marked Mixer Out on the Servo card is FP3Test port which is marked as 'Mon1' on the schematic (latest schematic). This channel is essentially the output of mixer buffered with gain 1 through an LT1128. Note that currently on North side, we are using FP2Test to send the PD signal in with an external mixer.

Something is either physically wrong near North PMC or the card might have developed some bug, which needs to be tested.


Code and Data

Attachment 1: BN_NPMCErr_CrossSpec.pdf  48 kB  Uploaded Thu Sep 5 20:46:53 2019  | Hide | Hide all
BN_NPMCErr_CrossSpec.pdf BN_NPMCErr_CrossSpec.pdf
ELOG V3.1.3-