How do I give a separate task ID to two compute waveform sub vi's running sumiltaneously in one vi?

Question

I'm running two compute waveform sub vi's in one main vi. The idea is to output two signals that I can vary independently to each other but when I hook LabVIEW up to a Oscilloscope, I only get one output and the other is just a flat line. I noticed that I'm unable to modify the subvi's independently ie: I change the duty cycle on one and its changed on both of them. Do I need to assign a separate task ID? If so, how do I do this?
Attachments:
analogtriggerattmemptwith2outputsignals_2.vi ‏247 KB

Answer 1

Hello;
In case you are outputing two waveforms to two analog output channels, you don't need to have two task IDs to accomplish that.
In case you want to vary one of the two waveforms and keep the other one stable, you can juct modify the buffer array of data points that will be output. Once you configure a analog output channels for two channels of the same DAQ device, you first setup a buffer of data, and such buffer is formed in a way that first data point goes to channel 0, second data poing goes to channel 1, third data point to channel 0 again, fourth data point to channel 1, and so on. That means you can alter only the data points that correspond to one of the channels, while keeping the other ones fixed. That will make only one analog output channel t
o change.
Hope this helps.
Filipe A.
Applications Engineer
National Instruments