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    User name R. Michaels

    Log entry time 17:38:09 on May 4,2003

    Entry number 99855

    keyword=helicity errors as indicator of deadtime burps

    Once again the helicity is an indicator of a problem. In runs 1577 and 1578 I see
    some "deadtime burps" which are periods of ~0.2 to 0.5 sec when the DAQ does
    not take data. Don't know why it happens, but would suggest you keep the rates
    at 4 kHz or below, and the deadtime at 10% or less. Also keep to a MINIMUM
    the number of processes including GUI's that run on adaql2, even if you are logged
    in somewhere else and just using the terminal. For the time being, one can assume
    the complaints from ESPACE (about "inconsistent" or "impossible" helicity) are
    probably an indicator of these burps, and monitor if they happen frequently.
    With the present helicity algorithms, the consequence of these burps is a loss of
    potentially 3 seconds each time, to reload the helicity. It probably doesn't have to
    be that bad, since : 1) The helicity data are ok; 2) The DAQ sub-components are
    in good synchronization; and 3) We have several redundant clocks in the data.