analog scan clock gating in DAQmx

[unagi]

Hi,

I'm trying to setup a .vi similar to the "Analog_Window_Acquisition.vi" found in the NI document "Acquiring Analog Input Within a Specified Range of Values". In the article it mentions that analog scan clock gating is the method by which one may acquire a selected part of the incoming signal based on a threshold window. "Unfortunately", this .vi is in Traditional DAQ, and I'd like to know if there are any known analogous VI(s) written in DAQmx.

I've tried using the 'Trigger and Gate' Express VI, but I'm not quite sure exactly what the 'Triggered Signal' output corresponds to with respect to AI. Namely, I do not see any settings for AI channel task, scan rates, etc., so is this VI just a 'filter' for a complete acquisition of a signal? (i.e., does one need to use the output of an initial (complete waveform) AI Read for the input signal to the Trigger and Gate.vi?)

Basically my goal is to acquire input pulses (square waves of low duty cycle) only during the pulse width (tens of milliseconds) to save on memory, prevent buffer overloads, and allow for more accurate sampling of the pulse width data.

Thanks!
Unagi

[unagi]

More specifically, I am trying to use the Trigger and Gate VI to capture analog input from two channels, with one of the channels providing the trigger input signal.

[Brett_B.]

Unagi,

There is an example program that is close to what you are trying to do. "Cont Acq & Chart Samples Int-Clock Pause Trigger.vi" is a DAQmx example program that ships with LabVIEW (help>>find example)...start with this. If you will change the trigger type to more-->pause-->analog window...you will be able to choose a range that is either "inside" or "outside" the window. You will also need to set the "top" and "bottom" options to bound your window. This setup should replicate in DAQmx the "Analog_Window_Acquisiition.vi" that you mentioned above.

If this doesn't work, repost and let me know what error you are getting.

cheers,
Brett