I am using a PXI-1000B with two PXI-6133 DAQ cards and I need to measure the relative phase difference between a reference sinusoid, acquired on one card, and a measured sinusoid aquired on the other card. So far my idea is to simply acquire N samples of both signas as waveform data and then compare. My problem is that I see a way to extract the relative phase information. How might I do this? Is there a better way of achieving this end?