louis.dartez@LIGO.ORG - posted 23:08, Tuesday 08 August 2023 - last comment - 23:22, Tuesday 08 August 2023(72075)
calibration improved after inclusion of ETMX L3 3.2kHz pole filter module in CAL-CS
I used Austin's PCALY to DeltaL external broadband measurement (LHO:72047), along with TJ's from late July (LHO:71760), to check the status of the LHO calibration before and after the return of the 3.2kHz "FHPole" ETMX-L3 filter module (LHO:72043).
The attached DTT screenshot shows PCALY2DELTAL_EXTERNAL (left column, uncorrected for TDCFs) and PCALY2GDS-CALIB_STRAIN (right column). The red traces show the two transfer functions after the filter change in LHO:72043 overlaid with the same taken before the change (grey traces). Looking at the right column, the PCALY_RX_PD_OUT / GDS-CALIB_STRAIN systematic error shows a significant improvement now.
The current calibration status at GDS-CALIB_STRAIN is better up to 450Hz so we should certainly keep the new ETMX L3 filter changes. The error in the region between 60Hz-100Hz has been improved from 6% to ~1.2%.
However, there is still more work to be done: we have near 4% error at the low frequencies and no good explanation for the 1% deviation above 50Hz.
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The low freq ~4% error seems to agree with what's modeled in the uncertainty estimates (e.g., see attached) -- that should be a known error.
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