VI gives error 200524

[natasftw]

The 6009 is a low-end DAQ device.  It's purely software timed.  This means you're going to have a VERY limited maximum sampling rate.  For most PWM applications, this rate is slow enough you won't be able to handle your application.

As a result, you should look at a DAQ device meant to do what you're doing.  That's why you were pointed towards a device with a counter.

[tuyenhoang7]

I understand now, I read a little more about why it is not possible with the 6009, and how other DAQs will be able to provide with what I need. 

Another question, though it's a little less related to LabVIEW itself: Instead of using PWM and/or a counter, can I implement/access a potentiometer in the DAQ controlled by LabVIEW that will limit the voltage output of the DAQ? If not, can I use an external potentiometer that I control through LabVIEW? That way, I can manually lower the output voltage of the DAQ from 5VDC, 5-10mA to something lower, potentially writing a VI that does that automatically. 

[smoores]

tuyenhoang7,

The analog output of the 6009 will allow you to select an output voltage between 0 and 5V with 12 bits of resolution.  Please see page 5 of the USB-6009 datasheet:

http://www.ni.com/datasheet/pdf/en/ds-218