trigger pwm with analog (again)

[beavercreek]

My application has two AI synchronized with CAN via RTSI.  I have AO triggered to the AI start to provide something for the UUT to deal with, and am trying to measure PWM output of my UUT, however I cannot figure out a way to trigger pulse width measurement or time it to my acquisition rate.  My vi has no loops as I need to sample at 2500Hz on the analogs, therefore I cannot request single reads (known as polling?) from the pulse width measurement.  The pwm I'm trying to measure can vary from ~10 to 4000Hz.

If i could coerce the pwm measurements into a waveform, then I could use get partial waveform for the samples that occured during the period of my analog measurement.  Then the only problem left to solve would be how to down(or up) sample to match my AI sample rate. 

Or is there a pin I can feed to the counter to only sample the PW when the analog has captured a point? 

If only i were smart enough to absorb all the nuggets on pwm measurement I've read in the last few days and meld them into my solution, I know its out there.

I'm using labview 7.0 and 6031E card   Thanks for any assistance!

[Erik_J]

Hi beavercreek,

Have you taken a look at the examples in the Example Finder?  There are some PWM examples that can be found by selecting Help » Find Examples » Hardware Input and Output » DAQmx » Counter Measurements » Period or Pulse Width.

A good example using the analog trigger can also be found in the Example Finder under Hardware Input and Output » DAQmx » Analog Measurements » Voltage » Cont Acq&Graph Voltage-Int Clk-Analog Start.vi.

You can use the analog start trigger in the example above to trigger your PWM Counter Input task.

I hope this helps!

Regards,
Erik

Message Edited by Erik J on 02-27-2007 09:41 AM