code for acquiring data not working like I'd expect

[winterfresh11]

Hello everyone. I posted my code that collects voltages from an NI 9215 DAQ card. I'm wondering why it acts so interestingly. For instance, at frequencys that are multiples of ten the waveform graph is frozen in place, and at lower frequencys (2-3 Hz) the data is changing faster rather than slower. Take a look! I'd like any input you have.

[RavensFan]

You are acquiring 10,000 samples at a rate of 100,000 samples per second.    So you are acquiring data 10 times per second.  If you acquiring signals that are a multiple of 10 Hz, then you are gathering integral number of cycles and it will look stationary on your waveform graph.

If you are looking at frequencies that are not a multiple of 10, or less than 10 Hz, then you are getting fractional or incomplete cycles in any given capture, and it will look like your sine wave is walking across the graph.