I hope using PXI-6115 multifunction DAQ card to measure a pulse height in special way. I use a two channels waveform generator creating two phase correlation pulse waveforms which have same frequency, as showing in attachment. Sending wide pulse to 6115 AI 0 , the narrow pulse is used as AI sampling clock and sending to PFI7. By this way every narrow pulse coming can get an data. For high frequency pulse I indeed can get the wide pulse height, but read data is zero when frequency is less than 1 KHz, is anybody know about this?