daqmx multiple modules are not working

[ColombiaHM]

Hi there, i'm working with cDAQ 9172 and I'm using NI9211, NI9201 & NI9265 to data aquisition system. We can work with 9211 and 9265 modules for taking thermocuple signals and for take current signals to control a system; now we need to synchronize a PWM with AC line (120v-60Hz), but when we use NI9201 module appear this warning:

Error -200022 occurred at DAQmx Start Task.vi:1       Resource requested by this task has already been reserved by a different task.

I try to use the same module without NI9211 and in this case there are no mistakes in the run process.

Here is the scenario, I hope anyone can help me.

[Schneiater]

Hi ColombiaHM,

This error happens when using cDAQ when you try ro run different aquisition rates.

A limitation of cDAQ9172 is that all the modules must be set for the same aquisition rates and run from the same DAQ Assistant.

When you configure the DAQ Assistant there is a blue "+" signal wher you can add other signals to aquire.

Feel free to ask more questions.

Regards,

[ColombiaHM]

Ok, there is another problem. In the VI the DAQAssitant block I add new signal with blue "+" and now I can measure voltage and themperature in the same process, thank for that. Now, I run the VI and apeears the following error:

Attempted to read samples that are no longer available. The requested sample was previously available, but has since been overwritten.

Increasing the buffer size, reading the data more frequently, or specifying a fixed number of samples to read instead of reading all available samples might correct the problem.

I read and many people say that this problem could be solved changing number of samples frequency, but I try with almost 5 different values and the error still there.

What can I do? How can I increase buffer size? What values of rate and number of samples can I use?

[Schneiater]

Hi ColombiaHM,

This error happens because of a buffer underflow. Your VI try to get samples of the buffer but the hardware didn't aquire this number of samples.

You can increase the rate or you should review the functions that are using the samples that you aquire with the DAQ Assistant and check if these other functions are handling more samples than you are aquiring.

Regards,

Rodrigo Schneiater