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    User name pking

    Log entry time 21:25:46 on June 04, 2010

    Entry number 324568

    keyword=ROC31 seems to be working now; changed nsamp to 905

    Investigation of the ROC31 problems found that the VQWK gate inhibit signal which is asserted at the beginning of the run was inverted (should be on output #7 of TIR with yellow wire to the right).

    Also, a number of samples setting of 925 seems to be too large for an IT setting of 2920. I changed the number of samples per block to 905.

    Calculation for nsamples:

       integrate_time = IT * 2.5 us = 7300 us
       integrate_time - VQWK delay = 7300 us - 42.5 us = 7257.5 us
       (integrate_time - VQWK delay)/nblocks = (7257.5 us)/4 = 1814.3 us
       nsamp = (integrate_time - VQWK delay)/nblocks/(2 us) = 907 samples

    I dropped it down to 905 for now.

    I am not sure why entry 324477 indicates that we had been able to run with a setting of 925 earlier, but not now. I would guess that the difference is in the T_settle period, which is now 100 us, and may have been 500 us when we were running with 925. A setting of 925 leads to a VQWK response about 160 us longer than 905, so we might have been pushing into the T_settle period earlier and now we're running into the next T_stable.

    Anyway, the PREX run type seems to work now, with these settings for the VQWK modules: