The easiest way to determine the capacity of a capacitor is the step response. The measurement basic´s you will find
here. To aquire voltage with your 6034 use for example the DAQ Assistant -> input configuration "voltage" or refer to the examples which shipped which LabVIEW (Help-> Find Example -> Hardware Input & Output -> analog measurement -> voltage).
The timing information is delivered from your daq-assistent and is dependent from sample rate.
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"another problem we want measure ac voltage use analog input
but the rms is not measure correct
itwas measured change"
-> Proposal: Aquire analog voltage -> Analyze received 1D-Array with complete subvi´s shipped with labview (you will find a vi called RMS.vi or mean.vi in the analyzed function palette -> or search in blockdiagram for RMS).