How to control phase between two sine waves using Daq Assistant.

[epsilon-delta]

I have a VI that uses a DAQ assistant configured for two analog output channels on a PXI-6289.  I use the outputs of two Sine Waveform VI's to build an array that is input to the DAQ assistant.  On the front panel there are controls for controlling the phase, amplitude, and offset for each of the two waveforms, and these controls are wired to the Sine Waveform VI inputs.  When I run the VI, the two waveforms are generated successfully.  While the VI is running I can control the amplitude, frequency, and offset of each waveform independently, but when I try to control the phase between the two waveforms, no phase shifting is observed.  Only when I stop the VI and restart it does the desired phase shift take place.  Why doesn't the phase control work like the other waveform controls?  I am using LabVIEW 8.6 on a Windows XP system.  Thanks in advance.

[EadieU]

How do you have the reset signal control set for the Sine Waveform VIs?  From the LabVIEW 8.6 Help for the Sine Waveform VI, "If TRUE, resets the phase to the phase control value and the time stamp to zero." 

Message Edited by EadieU on 02-13-2009 05:25 PM

[epsilon-delta]

Mark,

I am running the VI with the phase control set to TRUE.  If I set it to FALSE no phase shift occurs.

[EadieU]

Have you tried putting a waveform graph on the outputs of the Sine Waveform VIs to see if their output is changing as opposed to just the output of the DAQ Assistant.   

If it's just the DAQ Assistant, then you'll need to use basic DAQmx VIs.  Express VIs like the DAQ Assistant are great for many applications, but in your case you would want to program with the DAQmx VIs.  You can find basic examples for DAQmx with the LabVIEW Example Finder.  in LabVIEW, open the Example Finder by going to Help»Find Examples...  In the Example Finder, select Hardware Input and Output»DAQmx»Analog Generation»Voltage.  You can also specify your hardware, the PXI-6289, in thelower left corner of the Example Finder.