How to plot my data acquisition signal (dynamic data) and the mean values (scalar) on the same wave graph?

[sheck]

Hi,

I would like to plot my data acquisition signal (dynamic data) and the mean values (scalar) on the same wave graph.  I've tried using bundles and a variety of arrays .  But, no luck as of yet.  

Any thoughts?

Thanks-

Sherri

[Bob_Y.]

What do your mean values look like?  Scalars are hard to graph since a single point is not going to show up well. 

Anyway, have you tried to just wire the Scalar to the Dynamic Data Type wire and see what happens?  It should insert a merge signals and work OK. 

I think you might want to wire the mean into a Simulate Signals Express VI set to DC.  This will produce many points of the mean value.  Then when you graph the result, it will look like a line instead of a point.

[sheck]

Great!  Thanks, Bob.  I can't read your example vi b/c I have 7.0.  But, I think I know what to do now.  Thanks again!

Sherri

[sheck]

So, now that I have made these changes my "stop" button no longer works and the data acquisition time is very slow.  I'm not sure what I did wrong.  I've attached my vi below.  Thanks for any help-

Sherri

[Matt_S.]

Hi Sherri,

I'm not seeing the problem you're seeing with the "stop" button. It still works when I run the application you posted. As far as the data axquisition being slow, that's caused by a number of things.

A) You're using all Express VIs. They add a lot of functionality with very little programming, but are not extremely efficient.

B) You are doing software timed DAQ. Depending on your hardware you should probably go with hardware timed daq. That would give you deterministic timing instead of the results you're seeing now.

Hope this helps.

Matt S.

[sheck]

Hi Matt-

Thanks for the reply.  By "hardware timed daq", do you mean the data acquisition rate that is found with my daq card spec sheet?  For example,  the spec sheet states that i could sample at 100,000 samples/sec for one channel.

Thanks-

Sherri

[Matt_S.]

Hi Sherri,

That's correct. To see an example of doing hardware timed DAQ, you can open the example finder (Help -> find examples) open the following folders.

Hardware Input and Output

DAQmx

Analog Measurements

Voltage

From the Voltage folder you should see an example called "Cont Acq. and Graph Voltage - Int Clk.vi".That will give you a good idea of what I'm talking about.

Regards,

Matt S.

Applications Engineering

National Instruments

[sheck]

great!  thanks so much!

Sherri