J. Kissel

Here're the first results of looking at the channel's whose differential inputs I'd shorted to ground the other day (LHO:78302); the inputs to the AA chassis that feed ADC2 on the SEI H23 computer (and ADC2 is used to readout all of the HAM3 ISI's sensors and monitor signals.)

I'm happy to report that it's not that interesting:
    (1) We model all of these 16-bit, General Standards (16AI64SSA) ADC channels used in differential mode to asymptote to 3.6e-6 [V/rtHz], or ~4 [uV/rtHz] above 100 Hz, and to start getting worse than that below 10 Hz, eventually rising in noise inversely proportional to frequency ("rising with a 1/f slope below 10 Hz").
    (2) First attachment shows these four channels agree with, for the most part, with the asymptotes at 3.53e-6, 4.14e-6, 3.17e-6, and 3.24e-6 [V/rtHz] at 1000 Hz, so a range of 3.66e-6 +/- 13%, and the slope of noise increase at the low-frequency end agrees the xpected rise.
    (3) I'm a little bit sad that the 50-400 Hz region (see second attachment for zoom) which seems to have wide 5-20 Hz wide features that get as loud as 10 to 14 [uV/rtHz] at ~[55, 72, 95, 145, 165, 190, 220, 285, 370] Hz but I don't have time to investigate (e.g. the first thing I would do would be to check if these features have coherence with the other channels on this ADC that have real ISI sensor signals).

More to come on coupling to the DuoTone signals.