How to write data to the DAQ for a specified length of time while still reading the input data?

Question

Hello,
I'm using labview 2012 and am trying to turn on a signal for a specified length of time in labview at the press of a button. The signal goes into an AO (PXI 6723) through my system, where the voltage gets divided by 2, the read in through the AI (PXI 6225). I want to write and read voltage constantly and then have a spike of voltage after pressing a button in LabView while still reading the voltage value for the specified amount of time.
Parameters:
constant voltage of 1 volt to Analog output (reading and writing) seen through a waveform chart.
for 1 second, turn on 3 volts and see the response on the waveform chart.
My specified delay time does not match the elapsed time. I am having difficulties doing this. I have attached the VI.
 ( I can't upload a functional VI since it shows "the contents of the attachment doesn't match its file type") How can I attach the VI?.
Thanks!
Eduardo

Answer 1

Mike,
Thank you for your reply! I greatly appreciate it. I currently don't have any DAQmx timing in my application. I tried using it and, without really understanding how it works nor how to manipulate it, the whole test end up taking a long time to change the values i.e. too slow.
The DAQmx timing I used was the sample clock since it was for analog signals, but I don't really understand the buffer, what that means nor how to use it. inputting a rate time for it also made my test slower. The rate time is the samples per channel per second, but I'm not sure how to determine a number so that I am collecting the data I need and take into account aliasing.
I know the PXI 6225 has the capability to read 250kS/s (which I am assuming it's kilosamples per second or 250,000 samples per second). I am using 32 differential channels. I have read that I have to divide the maximum sample rate by the number of channels, (250kS/s / channels) but I don't know if I should count the number of total channels (64) or differential channels(32). In other words, is the per-channel maximum rate:
250,000/32 = 7,812.5 samples per channel per second, or
250,000/64 =3,906.25 samples per channel per second
Furthermore, If I know the number of samples per channel per second, how can I implement that knowledge to the DAQmx sample clock so that my sampling is as fast and as accurate as it can be?
I attached an image of my DAQmx functions in my code, I merged all the stacked sequence structures in paint so you can see them.
thanks for your help!
Eduardo
Attachments:
DAQmx tasks.jpg ‏211 KB