Two main problems with your VI:
- REmove both "Wait (ms)" from both while loops! You do not need them! The top while loop is timed by the DAQmx Read VI. The bottom loop is timed by the Queue.
- You read your 2 millions of data points as a waveform. But you coerce it in to a Dynamic data type. This can cause problems. Do you really need timing info in your file? Is that not enough you know you have 2MHz sampling rate, so you could just simply store the measured voltages as double...
- Do not use a waveform Graph in your top DAQ loop! Also, you really want to see 2 millions of data points at every second? You should do kind of decimation or averaging...
- To be efficient do not use a File Express VI in your consumer loop. Use a TDMS file function instead.
I would change the DAQmx Read to read double array, and also set the Queue to carry array.
