cDAQ Volts and Thermocouples in the same Task

[danny_t]

Hi

Using -  NI-CDAQ-9133 plus NI 9214 thermocouple cards and 9209 AI cards. 

I have playing around with the NI example Analog Input - Voltage and Thermocouple in a Single Task.vi and also tried creating NI-MAX tasks with the above combination. From the manuals I cannot see any reason these card will not work together in one task as in the example.

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P90VSAS&l=en-GB explains how the sample rate is dealt with between the different types of cards.

I have at this time no real hard ware and am therefore configured simulated devices in NI-Max.

Running the example selecting only the AI or the thermocouple both plots look reasonable, given what I know of the simulated devices.  I was expecting that when I enable both the AI and the thermocouple measurements that the results graph would be a combination of the two run independently, however the results values are not as expected. There are not errors and things look like they are working except for the generated results,

Could this be down to how the Simulated devices are acting, of is to single task idea not suitable for this combination of hardware.

cheers 

Danny

[GerdW]

Hi Danny,

I would use two DAQmx tasks: one per module...

[danny_t]

Hi GerdW,

I am interested in the rational behind your comment, is this from experience ? 

The C series device grouping says you can group both 9209 and 9214 channels together a Scanned Devices ok DAQmx tasks may be different.

I have with PXI chassis written Tasks that cross across numerous modules, though so far always the same type of module. 

cheers 

Danny

[James_W]

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@GerdW wrote:

Hi Danny,

I would use two DAQmx tasks: one per module...

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I'd second that. I don't think I've ever managed to setup a task running on 2 different physical devices in DAQmx. I don't think it's allowed, (but I think you can synchronise them in H/W on the cDAQ chassis)

James

[danny_t]

I’m not sure definition of device, but,

I have delivery a system been working over two years with a single task gathering  thermocouple data from 10 cards in a PXI rack, NI even help me at one point and we’re happy that is was a legitimate think you do.

NI supply an example of actually running a AI card and a thermocouple card, so it should be possible.

[James_W]

Ah ok.
It must be when I tried running tasks across 2 PXIs I fell a cropper then. - I learned to architect differently as a result.

James