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    User name jroche

    Log entry time 22:05:54 on September 28, 2010

    Entry number 333067

    This entry is a followup to: 333049

    keyword=TDC1875: scope picture of signals: common start or common stop?

    Refresher: Since we plugged the S2, S1 and Cerenkov tdc signal in the high resoltuion tdc 
    1875: we have not seen any tdc signal for these detectors out of the analyzer.
    I plugged a nim pulser in place of the signal out of the S2L9 pmt and looked at the signals 
    (gate and signal) at the face plate of the TDC. All other S2 pmts were off (HV off). Below is the 
    scope picture: the blue line is the signal that goes in the front input of the TDC called "cmn" 
    and the yellow signal is the S2L9 signal. So the pmt signal arrives 200ns before the gate. 
    Is this what we really want? The lecroy documentation on the tdc1875A says that this tdc is 
    working on the "Common Start Mode of Operation".
    I'll keep on poking at this tomorrow morning.
    Note: I left the pulser and the scope plugged. 

    A copy of this log entry has been emailed to: hisham@jlab.org

    Figure 1