9263 updating voltage out to slow

[bassinbc]

I am using a cDAQ 9172 with NI9263 VO and NI9205 VI modules. I want to read a voltage in (feedback) and adjust the voltage out to read some porportial value of the voltage in. The trouble I am having is that the 9263 seems to be to slow. I need to update the voltage out at 500 Hz. I don't seem to get anywhere near that fast. Any ideas?

[chrisger]

Hi there

LV 9.0 has just been released. Users with LV < 9.0 can't open your VI. Increase the chance to get some help by posting the VI in the lowest LV version possible (use the File\"Save as" menu item).

[bassinbc]

Ok here it is in 8.6

[RavensFan]

No.  That is still LV 2009.

[bassinbc]

Yea, and it wasn't even the correct one. Is it Monday?

[RavensFan]

You are doing 1 sample analog inputs and outputs.  One sample for each iteration of the loop.  That means your acquisition is essentially software timed.    Your acquisition can only be as fast as your software loop will run.

You should use N sample acquisition.  If you acquire 500 samples, the loop will only need to run once per second.  However you aren't really doing anything with the data other than displaying it in a scalar indicator.  The human eye won't be able to see 500 samples per second.  What do you really want to do with the data once you get it?  Graph it, analyze it, log it to file?

[bassinbc]

This will drive a pwm solenoid driver. The feedback (VI) will be coming from the UUT and the Eng on the project requested that the data be written at around 500 Hz. So what I need to do is monitor the VI and adjust the VO at a rate of 500 Hz. I am not sure if the VI and VO should be in sync, but I believe that it should. My current example doesn't address this. How would I sync the VI and VO modules? 

[RavensFan]

I would recommend browsing through the DAQmx examples in the Example Finder.  I'm sure there will be one there that does what you want.  Also search the forums for similar questions.

It may be a matter of sharing the clock between modules, but I'm not familiar with cDAQ to know exactly how they function.

[Brandon_B]

Hello bassinbc,

Ravens Fan is correct.  In order to synchronize two devices they will need to share the same sample clock and start trigger.   In LabVIEW, you can go to Help>>Find Examples.  Once in the example finder, select Hardware Input and Output>>DAQmx>>Synchronization.  From there you can select Multi-Device or Mult-Function.  In Multi-Function there is a VI specifically for AI and AO synchronization, but one thing that it is missing is the shared RefClk because the program assumes it is the same card.  Keep that in mind when choosing your program.

Regards,

[bassinbc]

Looking at the example, I don't see how to use the VI (inside the while loop -feedback) as input to the VO (outside the while loop).