CAR ID 208056 (SampleClockTimebase property incorrectly supported by cDAQ)

[RCampbell]

Hi Cristián,

Unfortunately, there is no way to add a timing engine to your cDAQ chassis.  Your best option is to put the 9219 in the same task as one of your other modules, as I explained in a previous post.  This Knowledge Base article might help explain it a little better.

One more thing to note: if you want to share the start trigger from your 9234 task with your other two tasks, you have to explicitly reserve the 9234 task first, then query the DAQmx Trigger: Start.Term property.  The following code snippet illustrates how do do this.  The reason for this is that DAQmx does not choose the timing engine until the task has been reserved.  So the start trigger terminal could be ai/StartTrigger, te0/StartTrigger, or te1/StartTrigger, depending on which timing engine DAQmx chooses for your task.  Reserving the master start trigger task and querying the Start.Term property guarantees you will provide your other tasks with the correct start trigger source terminal.

I hope this will help you get your application up and running.

Best Regards,

[crimolvic]

Thanks again Ryan,

that is a sound solution for ensuring the choice of the right timing engine. I had solved the hard way: by trial-and-error I came to know which timing engine was assigned to each task by DAQmx and then assigned it properly. I will surely change this.

[crimolvic]

Regarding the 9219 contained in a task from a faster device, say the one of the 9234. Can this be done even if the data type being acquired is different (e.g. Current at 100 Hz with the 9219 and Acceleration at 51200 Hz with the 9234)? It this solution not limited to the case of having the same input type (e.g. Voltage in both devices)?

Regards,

Cristián

[RCampbell]

You can mix different channel types in the same task, as long as you use separate Create Channel VIs for each different measurement task.  You can just wire the task output from the first Create Channel VI into the task input of the second Create Channel VI.  You can also set the timing mode on the 9219 to High Speed, which guarantees that 9219 will run at 100Hz.  Since the sample rate will be set to 51.2kHz, the 9219 will return 512 repeated data points for each actual data point.

[crimolvic]

Ok, that I didn't know it can be done. So aftterwards, only one of the repeated samples should be left and issue solved.

Many thanks, you have been very helpful to me.

Regards,

Cristián