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AdV-SAT (Suspension control upgrade)

swinkels - 13:47 Friday 10 May 2019 (45858)

DAC level crossing glitches in NI_F7

While looking at some random suspension channels to try to understand diffused light, I found by chance that some of the NI_F7_LVDT signals are very glitchy. The glitches occur at the moment the corrections on some coils cross 0.174 Volt, so this seems a classical case of a broken DAC channel. Since several coils are driven with the exact same correction, the exact channel cannot be identified. I have no evidence that this noise is visible in the sensitivity, but it seems better to resolve any issues on the suspensions of our main test masses.

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Comments to this report:

Boschi, Ruggi - 16:25 Friday 10 May 2019 (45862)

A similar behavior can be observed on other SAs (see for example WE in figure) and is very likely due to the effect of cross-coupling of the F7 co-located Sensor/Actuator design. In any case a test on the CD board can be easily done in one of the next maintenance shifts.

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