xavier.siemens@LIGO.ORG - posted 12:25, Friday 22 May 2015 - last comment - 13:35, Friday 22 May 2015(18581)
More timing checks: the I/O chassis ADC and DAC duotone channels
I looked at the following channels: H1:IOP-SUS_EX_ADC_DT_OUT_DQ H1:IOP-SUS_EY_ADC_DT_OUT_DQ H1:IOP-LSC0_ADC_DT_OUT_DQ H1:IOP-SUS_EX_DAC_DT_OUT_DQ H1:IOP-SUS_EY_DAC_DT_OUT_DQ H1:IOP-LSC0_DAC_DT_OUT_DQ Attached are 6 figures, broadband and close-ups to the 960/961Hz signals. Notable features: 1) The EY spectra don't look right at all. The doutone signal is missing (SUSEYcloseup.pdf) and the spectrum has a positive slope (SUSEY.pdf). 2) All of the plots show a comb of 1Hz harmonics. Probably not surprising. 3) All the DAC channels (in blue) show extra noise (see all the non-closeup).
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Dave Barker informed me that there shouldn't be any signals on the SUS_EX/EY_DAC_DT_OUT_DQ channels so that the absence of a duotone signal in EY is fine. In fact we turned off the EX signal. Now the spectra for the EX/EY ADC/DAC look very similar so there's no reason to be alarmed. We still don't understand why (now both EX and EY) DAC signals show a positive slope.