christopher.kucharczyk@LIGO.ORG - posted 15:06, Wednesday 07 March 2012 - last comment - 16:43, Wednesday 07 March 2012(2383)
The beginning of the excitation in the ISI CDMON and IOP DAC
Brian and I have plotted the beginning of the (bad) excitation in dataviewer in both the ISI and IOP models. We have also plotted the GPS time according to the ISI model (DCU_ID 75). As you can see, the GPS time drops out when the model is being off, but comes back up shortly thereafter. This data is for the 11:42 UTC restart when the excitation starts. We plot the same for the second restart, twenty minutes after which the fiber break occurs. We see the same thing - the model is shut down, then starts again. We see a similar drop in the GPS time to 0 before the model restarts. The excitations also stop when the model stops, and start again when the model restarts. We see a growth in the amplitude of the coil drive signal as well as the DAC signal from the IOP. This is not inconsistent with a loop instability within the model.
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We have also plotted the actual signals that the IOP was driving during the entire event. What's most interesting is that the signals on all channels appear to be max-ed out during the whoe event, except for ST2_V3, which drops out about five or six hours into the excitation, then returns upon a later model rebuild. The signal drops out after the 15:57 PST rebuild and returns after the 16:38 rebuild. Unsure what this entails.
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