missing first part of waveform

[R_Beauchaine]

Hi, I am measuring a current pulse across a 1ohm resistor into a diffential channel of a PXI 6281 card (via the SCB-68). A scope across the input terminals sees the proper 40mS wide waveform. The daq card is missing the 1st roughly 30Ms of the waveform. Also, it has a long rise time on the order of a few mS, as opposed to the scope reading rise time of a few microseconds. I am software triggering before I even issue the pulse and can see the off readings preceding the pulse. I have no filtering at the input to the ADC. There are no other channels in the task and no other tasks running.

Any ideas on the problem are appreciated.

Thanks, Rick

[R_Beauchaine]

    Have figured out the problem. Current source (cap discharge) being controlled by FET to maintain 4A so individual differential legs saturating IA until discharges enough to be in range.

Thank you, Rick