As Jim pointed out in 48854, this sensor's noise has been elevated for many weeks.  This morning, we transitioned the ITMX ISI to Isolated Damped to take the CPSs out of the control loop.  The IFO survived this but when the cable was unplugged from the rack, the output went to the far limit rail.  This would have tripped the ISI WD but we had increased the WD Limit, smart.  When the card was removed from the rack, the signal went to zero.  After a minute of so, the card was replaced.  And the ISI was returned to the nominal configuration of Fully Isolated.  Sadly, while the IFO survived the transition of the ISI stage2 to damped, it could not tolerate my banging around with the ladder and bumping my head (w/bump cap, smart) on the suspended HEPI, dummy.

Below is a comparison of the ITMX stage2 CPSs that Jim posted last night and one from just an hour ago.  Clearly the noise is reduced but H3 remains noisier than the others of the stage.  If this continues to be of concern, we'll take the next step of power cycling the CPS interface.  That however, will require the platform to go into fully Damped which the IFO is not likely to survive, but, we'll see.