Simulate Signal phase output is only adjustable in increments of 4 degrees.

[epsilon-delta]

I am using two simulate signal express nodes to produce two square waves.  These signals are combined using a Merge Signals node and the output is connected to the data input of a DAQ Assistant node.  The two square waves are output on a PXI-6289.  All of this is placed inside a While Loop.  This VI works fine and allows me to change phase between the two waveforms while the VI is running, and there is no jitter observable on the waveforms.  Phase is controlled via the inputs to the two Simulate Signal nodes.  The problem is that the phase is only controllable in 4 degree increments.  I am overlooking something, or is this a LabVIEW bug?

[CharlesD]

How exactly are you determining the phase difference between the two Simulate Signals Express VIs?  Are you simply wiring in two controls to the individual simulate signal Express VIs?  Could you attach a screenshot of your code to help me understand exactly what is going into those simulate signals VIs?  I created a similar program and I was able to create waveforms with phase differences that are not a multiple of 4deg and it seems like there is no problem. 

Thank you, 

[epsilon-delta]

Hello Charles,

Thank you for your response.  I am attaching a couple of VI's for you to examine.  I have placed a note at the top of each front panel describing what the problem is.  In summary, they both have a problem of 4 degree phase resolution.  One allows phase adjustment  while the VI is running, but the other does not.

[CharlesD]

Hello,

I was able tocreate a similar application.  I create two signals with a given phase difference using the express Simulate Signals VI.  I then Write those two signals to my m-series board ontwo of my Analog Output channels.  From this I wire those two signals to two of my analog input channels and read in the signals.  From this I measure the phase difference using the Amplitude and Phase spectrum.VI .  You will notice from the attached screenshots that i can get any phase difference that I need- in this case I chose a phase difference of 9deg.  it is a little off but that is becasue I'm trying to calculate phase of two signals using an M-series card which is a multiplexed device.  It will never be 100% accurate.  To accurately measure the phase difference between two signals you would need a simultaneously sampling DAQ card or DSA card.  

My question then for you is how are you measuring your phase difference because the way you are doing your application should be fine.  if you want to double check try implementing my attached VI and see if you still get the same problem. 

Let us know of it shapes up!

[epsilon-delta]

Charles,

Thank you for your response and suggestions.  I use digital and analog oscilloscopes to observe the waveforms and measure the phase difference.  Is there any way you could send the actual VI you mentioned?  The .png file showing the block diagram is unreadable in some places and some of the VI's are not identifiable. 

epsilon-delta

[CharlesD]

Attached is the vi hope this helps.Good luck!