Problem with cDAQ 9171 and 9212

[chrisff]

I have a cDAQ 9171 chassis and 9212 Temperature module. According to the cDAQ 9171 chassis specs it has 3 timing engines and can accomodate 6 simultaneous tasks. The 9212 specs indicate that the module supports simultaneous sampling as it has a dedicated ADC for each of its 8 channels.

If I define a single task and one or more channels I can retrieve data without a problem.

However if I define two separate tasks, say task0 with channel ai0 and task1 with channel ai1, I get resource conflict errors. What I want to do is acquire data from ai0, then at a later time acquire data from ai1. I have scoured these discussion forums and NI documentation trying to understand why this doesn't work when my hardware apparently supports multiple tasks. Also to confuse matters further, contrary to the specs, I also read over and over again in forum posts that you can only have one task running per chassis. 

Can anyone help me understand why what I'm trying to do is not working and perhaps what the chassis specs actually mean.

[natasftw]

The specs on the module mean that each task can run at the maximum rate.  In some modules, you have a single ADC/DAC so you run into a situation where adding a second channel cuts your maximum rate in half.  Having four cuts it to a quarter, etc.  With the simultaenous, you can run each at the maximum rate.  But, you'll still need to setup all of them in the same task.  Otherwise, the software will reserve that module for the first task.

[chrisff]

Thanks. Apprecaite your help. The module part is clear. But what does the "6 simultaneous tasks" on the 9171 chassis mean and how do those tasks relate to an acquisition task set up in software?

[chrisff]

So can anyone help me out with the second part of my question, namely  what does the "6 simultaneous tasks" on the 9171 chassis mean and how do those tasks relate to an acquisition task set up in software?

[benthere]

Chrisff,

The 6 simultaneous tasks means the cDAQ-9171 is capable of running those tasks at the same time. Check out this KB for some more information on that: https://www.ni.com/en/support/documentation/supplemental/18/number-of-concurrent-tasks-on-a-compactd...

Thanks,