Relative time management in LabView

[pedrom]

Hi All, 

I'm new to LabView so I wanted to get some ideas on how to get started on the following task.   I have a PXI system and what I need to do is control an experiment with very precise timing (millisecond) .   I need to send out triggers or ramp up dc voltages but everything needs to be done at a well known time.   The experiment would start at  t=0 milliseconds and I would want to be able to tell it to do something at a time relative to t=0ms.   

What is the best approach to acomplish this with the timing and triggering features offered by DAQmx?   I would be glad to hear any suggestions that come to mind.

Thanks

Pedro.

[Nathan_R]

Hi Pedro,

If you need to send out digital triggers with 1ms accuracy I would recommend doing hardware timed digital output assuming you have a DAQ card that supports it. Most M-Series cards do. With this type of output task you can provide a digital waveform that is output timed to an external clock. You can use one of the DAQ cards on-board counters to generate this clock. It sounds like 1kHz would work for you Then a sample in the digital waveform would output each ms. An example of how to setup the digital task can be found in the LabVIEW  Example Finder. Go to Help >> Find Examples… >> Hardware Input and Output >> DAQmx >> Digital Generation >> Write Dig Chan-Ext Clk.vi.  An example of using a counter to generate a clock is under Hardware Input and Output >> DAQmx >> Generating Digital Pulses >> Gen Dig Pulse Train-Continuous.vi.

Since you said you were new to LabVIEW and DAQmx the Developer Zone article, Learn 10 Functions in NI-DAQmx and Handle 80 Percent of Your Data Acquisition Applications, is a great resource for getting started with DAQmx.

Please let me know if you have any questions and take care.

Thanks,