NI 9211 slow response with cDAQ modules

[mrmirrorthedrummer]

Hi everyone,

I have a NI cDAQ 9178 and a thermocouple acquisition card NI-9211. I just want to acquire temperature measurements at 2 Hz. However, when I create a task with DAQ assistant asking for one sample on demand (in a while loop running at 2 Hz) I have a very slow response from the module. The acquisition occurs no faster than 1,5 – 2 seconds. If I test the single channels in NI MAX everything is working just fine.

I am aware this thermocouple module is a “slow one”, but according to the specs it has a max sample rate of 14 samples per second, which is far more than one sample every 2 Hz. Indeed, if I change the acquisition mode and run the loop every 2 seconds asking for 10 samples, the card works. It just has problems with “one sample on demand” acquisition. I also tried with a CDAQ 9174 (4 slots available instead of 8).

I also experienced this problem initially with a 16-thermocouple DAQ card NI-9213. However, in this case it is possible to select a “high speed” acquisition mode rather than a “high resolution” mode when you create a task with daq assistant. With this option all the problems disappear. Unfortunately, it seems that the NI-9211 card does not have this option.

The most surprising and annoying things above all is that if I plug the NI-9211 card into a usb-9162 slot (single slot just powered by USB) and I run the same loop at 2 Hz, the module is working just fine!

Because of this, I would actually assume that there is some problem between the cDAQ 9178 and the 9211.

If I look here, there should be no compatibility issue.

http://www.ni.com/product-documentation/8136/en/

but the truth is, that any while loop with a task from 9211 module runs no faster than 1,5-2 sec if the card is configured with “one sample on demand” mode and is connected to a multiple slot carrier instead of a single dedicated one.

Has anyone ever experienced this as well?

And do you know if there is any solution?

I have LabVIEW 2010.

[SJSimpson]

I have exactly the same problem

I have a program that reads and writes analog and digital data. Single samples on demand. The AI is in one loop at 10ms interval. The AO and DO is in another at 5ms intervals. I have setup loop timers in both loops to measure the time the loop takes to iterate.

When I use the program with a ni6009 hardware both loops run as they should at 5 and 10ms respectively.

When I use a cDAQ 9174 chassis with the appropriate cards both loops run at upto and beyond 80ms!! Making the program unbearably slow.

Are cDAQ chassis not capable of single point real time communication?

Is it a cDAQ rio I require or whatever they are called?

Could some one point me into the right direction here as I'm stuck. I have narrowed it down to the hardware as I am using the same program for both tests just changing the inputs and outputs channels/lines in the task.

Below are screenshots of the loops but as I said this same program works fine with the ni6009 but slow with the cDAQ?

Any thoughts?

[ZYOng]

Kindly please attach your program so that we can understand if you are configuring your code correctly.

Instead of using the DAQ assistant,  you may also want to try the shipping examples at Help >> Find Examples... >> Hardware Input and Output >> DAQmx >> Analog Input