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Entry  Mon Nov 3 15:16:28 2014, Dmass, Noise Hunting, Noise Budget, New beat spectrum: ErrSigs.pngBeatNz.png
    Reply  Mon Nov 3 16:15:21 2014, Dmass, Noise Hunting, Noise Budget, Beat spectrum not ltd by  
       Reply  Mon Nov 3 20:27:28 2014, Dmass, Noise Hunting, Noise Budget, ISS servo fail? 
          Reply  Wed Nov 19 14:54:36 2014, nicolas, Noise Hunting, Noise Budget, ISS servo fail?  
       Reply  Tue Dec 2 22:51:52 2014, Dmass, Noise Hunting, Noise Budget, Beat spectrum not ltd by  PDH_demod_chain.png
          Reply  Sat Sep 12 14:25:05 2015, Dmass, Noise Hunting, Noise Budget, Beat spectrum not ltd by  
    Reply  Mon Nov 3 20:36:14 2014, Dmass, Noise Hunting, Noise Budget, New beat spectrum: 
       Reply  Tue Nov 25 22:45:43 2014, Dmass, Noise Hunting, Noise Budget, New beat spectrum: 
          Reply  Wed Dec 3 17:02:31 2014, Dmass, Noise Hunting, Noise Budget, Noise budget cleaning up 
             Reply  Thu Dec 4 02:45:49 2014, Dmass, Noise Hunting, Noise Budget, Noise budget cleaning up PDH_sensing_nz.pngLB1005inputNoise.png
                Reply  Sun Dec 7 12:42:55 2014, rana, Noise Hunting, Noise Budget, Scatter Noise hump is RAM 
Message ID: 1166     Entry time: Wed Nov 19 14:54:36 2014     In reply to: 1164
Author: nicolas 
Type: Noise Hunting 
Category: Noise Budget 
Subject: ISS servo fail?  

Quote:

I tried to implement the ISS servo today for the east path with little to no success

It it not clear to me that the servo was engineered with the actual driver in mind

The AOM driver is only linear over a narrow input range: [156mV to 450 mV]  (can be + or -)

The ISS board seems to go to not have this offset built in, and it is not clear if the excitation inputs would be an appropriate place to add this.

I played around with using terminators on the input and output signals to try to force the DC value at the output of the ISS board to the middle of the linear range, but could not get the loop to do any actual intensity noise suppression for any switching state on the front

I punt to Nic, interim king of ISS servo board, following the passing of Prince Chaz, rightful heir to the throne, to determine what the correct way to sum an offset into the output of the board is.

 It's not pretty, but the servo will create the output offset internally because of the low frequency boost and integrator. When you close the loop, it will push the driver into the linear range.

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