Multifunction DAQ
DAQmx Timing VI
The Samples Per Channel is setting the buffer size in samples and the Rate is the sample rate in Samples/second. Not sure what else you are looking for.
Ok, I will assume you understand Rate since that is very basic.
With the DAQmx Timing.vi, you are setting the buffer size. This is how much memory is allocated for the circular buffer that holds the sampled data until you read it with the DAQmx Read.vi.
If you set up your task to be Finite Samples, this is how many samples the task will read before stopping itself. Use DAQmx Read to read all of the data (count = -1).
If your task is set up as Continuous Samples, then you are stating how many samples to hold in the circular buffer. When you do the DAQmx Read, you are getting data from that buffer (and moving the "read pointer"). If you let your buffer fill up (the "write pointer" comes back around and catches the "read pointer"), you will get an error. In your example, if you do not read any of the data in 20 seconds, you will get a buffer overflow error when you try to read the data. Generally, for Continuous Samples you want to just leave the Samples Per Channel unwired.
@nyc_(is_out_of_here) wrote:
buffer size = 2000 samples
rate = 100 samples/second
So, it will take 20 seconds to write the entire waveform ?
If you wrote a 2000 sample waveform, then it will take 20 seconds for the board to output that signal.
Everything works exactly the same as with a read, except the data is going in the opposite direction (you write to the buffer and the DAQ board will clock out a sample at the rate you gave it until all of the buffer has been outputted). You do not have to write the entire buffer. This is just how many samples are allowed to be in the buffer. Again, you are better off just leaving that unwired.
