J. Kissel

In order to facilitate further investigations of self-noise (LHO:67262) and aliasing (e.g. LHO:67297) in the new OMC DCPD 524 kHz ADC signal chain, I've installed a DB9 "plug" that shorts the differential pins of the ADC channels for the spare input of the "pass through and copy" AA chassis (D2300115, S2300016) in CER rack SQZ-C1 U40 (discussed in LHO:67439).

While the data is not stored in the frames, and one can only access at most 3 test points (i.e. take an ASD of a channel) at once from the new 524 kHz model, the channels 
    H1:IOP-OMC0_MADC0_EPICS_CH${n}

    Analog      Diff       Copies in
    Pins        Channel    ADC channel ${n}
    1-6         CH17       16, 20, 24, 28, 
    2-7         CH18       17, 21, 25, 29, 
    3-8         CH19       18, 22, 26, 30, 
    4-9         CH20       19, 23, 27, (31 is overwritten by the ADC duotone signal).
are now measuring the self noise of the differential system from the passthrough AA into through ADC.

Attached are pictures of 
    - the inside of the shorting "plug"
    - the fully assembled plug
    - the plug installed in the AA chassis
    - a zoom in of the installed plug