Hello,
You are right that increasing the rate means more samples per second.
It means the following: If you keep the finite number of samples to
acquire fix, then increasing the rate should decrease your acquisition
time. Suppose you are performing acquisition in a loop. If the
acquisition time decreases, then the time for a loop iteration will
decrease as well.
For example, for an acquisition of 1Hz, if the number of samples to
acquire (on the timing VI) is 1000, it means that you will acquire a
total of 1000 Samples. Since the rate is 1Hz, it will take you 1000
seconds to acquire all the samples. However, in a loop, you can use the
DAQmx Read VI to read part of the total number of samples already
available. So for example, if you specify 50 samples to read on the
DAQmx VI, every time it is called, it will grab 50 samples from the
buffer. If the samples are not available yet, it will wait until they
are availble or there is timeout and return. Now if you have a
process in the loop that take more than 50 seconds to comple before you
read again, then there will always be at least 50 samples in the buffer
from the second iteration. From there on, if you increase the rate, it
will just increase the number of samples availble to be read, but it
will not necessary make the other process in the loop faster. So the
DAQmx Read will always have the 50 samples it needs, but the other
process will still take time. So in this case, changing the rate from
1Hz to 100Hz will seem to have no effect on the entire process.
The important thing is to understand what those numbers actually mean.
-Sample per channel in the timing VI represents the total number
of samples to be acquired by the board on each channel of the task.
-Rate represents the rate at which the samples above are acquired
-Sample per channel in the DAQmxRead VI represents the number of
samples you want the VI to grab from the buffer. Those samples
have already been acquired and stored on the computer.
Hope this clears it all
