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Message ID: 9935     Entry time: Fri May 9 04:09:39 2014
Author: Jenne 
Type: Update 
Category: LSC 
Subject: CM board boost turn-on checkout 

As part of checking the common mode board before we get too carried away with using it, I looked at the time series of the AO servo output when I turned on various boosts, or changed gain values.  As it turns out, basically anything that I did caused glitches.  Oooops.

I plugged a function generator to the IN1 port of the CM board, with a freq of 400Hz, and a voltage of 10mVpp (which is the smallest value that it would allow).  I plugged the BNC version of the servo output into a 300MHz 'scope.

First I looked at "boost" and "super boost", and then I looked at various steps of the AO gain slider.  For all of the button presses that gave me glitches, I saved .png's of the 'scope screen (on a floppy, so I'll have to fetch the data tomorrow...).

Both enabling, and disabling the "Boost" button gave me glitches.

For "Super Boost", I saw glitches for all of the steps, 0->1, 1->2, 2->3. 

For the AO path, I only started at 0dB, and only captured screenshots of glitches when I increased the gain, since presumably that's when we'll care the most during acquisition.  I found that going down in gain caused glitches at every step!  For increasing the gain, steps from an odd number of dBs to an even number consistently caused glitches.  Steps from an even number to an odd number occasionally caused glitches, but they weren't very common.  For the steps that did cause glitches, some were worse than others (7dB to 8dB, 15 dB to 16 dB, and 23 dB to 24 dB seemed the worst.)

After my work, I put all of the cables back, so that we should be ready to utilize the CM board for locking this evening.

For posterity, here are the notes that I took while I was working - I'll make them more coherent when I fold them in with my images tomorrow.  The "first .png, next, etc." are because the 'scope numbers them in order as a default.

1st png = boost enable, then disable
2nd png = super boost, start at 0, then 1, then 2, then 3
3rd png = AO gain from 1 to 0
4th is AO gain from 0 to 1 (happens less often than 1->0, which is every time I get a glitch)
Next is AO gain 1->2, got 2 glitches!
3->2 glitch often, 2->3 much less often
next is 2->3
next png is 3->4, 2 glitches with weird dip
4->5, rare
next png is 5->6
6->7 is rare
next png is 7->8, which is nasty!!
8->9 is rare
png 9->10
10->11 is rare
png 11-> 12, 3 glitches
 12->13 rare
png 13->14, 2 glitches
14->15, rare
png 15->16, kind of nasty
png 17->18, 2 glitches
png 19->20, 3 glitches
png 21->22, 2 glitches
png 23->24, kind of nasty
png 25->26, 2 glitches
png 27->28, 3 glitches, at least
png 29->30, 2 glitches


Somehow, the images got put into a whole new entry, even though I thought I was editing this one.  Anyhow, please see elog 9938.

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