Acquire analog data using a trigger via an E series card

[carroll]

I would like to generate a square wave signal at a specified frequency which then would be used to trigger an analog data acquisition

[JoeFriedchicken]

Hi carrol,

I'm a little confused by your post. Using a square wave for a trigger is not a typical approach. A trigger is a one-time event -- when a DAQ board sees the trigger, it performs an action. Usually, it starts an acquisition or marks a reference in a group of samples. When using a square wave for a trigger, the first pulse will be the trigger and cause the DAQ card to react. The following pulses would then be ignored.

If you want to take a measurement for each pulse in the square wave, then you want to use that signal as the sample clock -- whenever the square wave pulses, the DAQ card will take a sample. I think this is what you meant, but if not, let me know.

The easiest way to acquire analog samples at a clock rate is use one of the shipping examples:

LabVIEW
C:\Program Files\National Instruments\LabVIEW <version>\examples\DAQmx\Analog In\Measure Voltage.llb

Text Based (C/VB6/.NET)
C:\Documents and Settings\All Users\Documents\National Instruments\NI-DAQ\Examples

Both have an example called 'Cont Acq-Int Clk' which uses the board's internal clock to drive the analog input sample rate. I think this will be a great starting place for your application.