Samples to Read is
NOT a graph scaling issue. The sample rate tells the DAQ board how fast to accumulate samples in the buffer. The number of samples tells the board how many samples to accumulate in the buffer
before doing a transfer. With a sample rate of .5 hz, if you specified number of samples to be 2, you would get 2 samples every second. As already explained, specifying 1000 samples makes your program unresponsive but it is unresponsive because of what you have specified.
