Multiple DAQmx tasks from multiple DAQ modules

[Akuaku]

Hi!

I am building a voltage measurement program that is to do in-situ measurement from 4 (or 5) DAQ modules that are NI-9205 (and NI-9223) that are connected to dock NI-9178. I have built 4 separate data sampling tasks but am getting an error that the task is already in use... I've found out that the dock is able to only have simultaneous tasks on 3 modules at a time...

What would be an elegant way to measure all of these modules in the same program in parallel. Must I create loops where I start and stop the task in a sequence? That seems like a hassle.. Is there anotherway?

I can provide my VI if necessary but it is just 4 parallel DAQmx measurement tasks in one while loop. Similar to this but 4x:

[GerdW]

Hi Akuaku,

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@Akuaku wrote:

I am building a voltage measurement program that is to do in-situ measurement from 4 (or 5) DAQ modules that are NI-9205 (and NI-9223) that are connected to dock NI-9178.

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Can't you put all/several modules into just one task?

Btw. the cDAQ9178 is called "chassis" (instead of "dock")…

[Akuaku]

If I can then that is very good solution. I've tried that though but perhaps did that wrong....

I've input the channels as follows: "cDAQ1Mod4/ai0:5;cDAQ1Mod5/ai0:5;cDAQ1Mod6/ai0:5;cDAQ1Mod7/ai0:5" but this is probably the wrong input.... How should this be done?

Also, now that I learned this is a possibility, can I add a NI-9219 resistance measurement to the same task? Or are AI-voltage and AI-resistance measurements always separate tasks?

Thanks for the help GerdW!

[GerdW]

Hi Akuaku,

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@Akuaku wrote:

I've input the channels as follows: "cDAQ1Mod4/ai0:5;cDAQ1Mod5/ai0:5;cDAQ1Mod6/ai0:5;cDAQ1Mod7/ai0:5" but this is probably the wrong input.... How should this be done?

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Do you get an error for the DAQmx task?

Can you attach your VI?

Did you select the channels using the channel reference selector?

Why do you use just 6 channels per module, when a single NI9205 offers 32 channels? Why do you need 4 modules, when one module can handle the job?

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@Akuaku wrote:

Also, now that I learned this is a possibility, can I add a NI-9219 resistance measurement to the same task? Or are AI-voltage and AI-resistance measurements always separate tasks?

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Let's start with your basic voltage measurement and handle other measurement channels once the voltage signals are working correctly…

[JensG69]

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@Akuaku wrote:

If I can then that is very good solution. I've tried that though but perhaps did that wrong....

I've input the channels as follows: "cDAQ1Mod4/ai0:5;cDAQ1Mod5/ai0:5;cDAQ1Mod6/ai0:5;cDAQ1Mod7/ai0:5" but this is probably the wrong input.... How should this be done?

Also, now that I learned this is a possibility, can I add a NI-9219 resistance measurement to the same task? Or are AI-voltage and AI-resistance measurements always separate tasks?

Thanks for the help GerdW!

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Please mention which modules you are using in which slot.
It might be useful to start more than one task, e.g. because a 9223 offers a sample rate of 1MS/s for each channel compared to the aggreate 250 kS/s of a 9205.

Yes, it should be possible to add a NI-9219 to an 9205-task. I recently did this with a 9205 & 9217 module, and the 9217 is fairly similar to the 9219.

Regards, Jens

[Akuaku]

Hi Gerd!

I get the following error with the input channels: Error 200279 which is that the hardware is not able to keep up with the program. I suspect there is something wrong with my channel configuration however. 

I attached the VI. There are the voltage measurements from modules 4-7. Also another task measuring the resistances from module 1. Im trying to include the resistance measurement in the same task if possible. 

I dont use all the channels and use multiple modules because in another program I need to up the sampling rate of the channels and the module is capable only to a total 250kS/s. More modules provide sufficient sampling rate. 

[Akuaku]

Hi Jens!

I included the VI in another message. I use modules 5 through 7 for NI 9205 and module 8 for 9223. I also have universal modules 9219 in slots 1-3. 

In this application the sampling rates and measurement specs for the 9205 and 9223 modules are the same so in that sense I could run them with the same Timing block if that is possible. 

[JensG69]

Some basic math:

You start your 9219 task with a daq-rate of 200 S/s, and then request 50 samples per channel on each read -> i.e. 0.25 s per DAQmx Read.

You start your 9205 task with a daq-rate of 240 S/s, and then request 10 samples channel on each read -> i.e. 0.04167 s per DAQmx Read.

Both Reads are inside the same while loop, hence the software buffer of your second task will overflow in short time, leading to error -200279.

EDIT: Solution: either run both task in independent loops or use a "-1" at the DAQmx-Read input at one of your two read-VIs.

Regards, Jens