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Timing between digital output and picture events

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  • Timing between digital output and picture events

    Dear Cedrus community,

    I am setting up an EEG experiment using SuperLab 4.03. The SuperLab is connected to a DC input of our EEG sistem, via MC PCI card, to record event markers. Event markers are DigitalOutput.

    The event markers should synchronize for stimulus events--there seems to be a problem. I tied an event sequence, which was:

    fixation corss - Picture event (20 ms) - Digital output (raise line) - mask event (80 ms) - Digital output (lower line)

    with this sequence, I hoped to send marker signal, like:

    _____---___________ (DC __ 0V, -- 5V)
    ++++PPMMMMMMMM (+,P and M are display refresh(100Hz) for fixaton, picture and mask)

    Instead I got:

    _____------------____
    ++++PPMMMMMMMM


    There is about 50 ms delay between marker onset and lowering line. I would appreciate if you could tell me how to avoid thd delay (or a better way to send a marker to an external device).

    CN
    CN
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