Virtual Oscilloscope; Tuning Data Acquisition Rate

[Fievels]

Hi everyone!  I have been attempting to program an oscilloscope using Labview software and USB-6009 DAQ.  It is very close to completion, but I cannot seem to tune the data acquision rate to the right speed.  Let me show you what I am talking about:

waveform dt: 0.1

Frequency:  Accurate

Limit: 5 Hz

Explanation:  " [0.1 dt] That is 10Hz.  So based on Nyquist, 5Hz is the maximum frequency you can sample.  Anything more than that will alias down into the 0-5Hz range."   -Crossrulz

waveform dt: 0.001

Frequency:  x100

Limit: 500 Hz

Explanation:  ????? The frequency seems to be dividing by dt at some point.

I would love for this oscilloscope to simultaniously read faster than 5 Hz and be accurate.  Here is my block diagram if anyone would be willing to take a look:

Create Channel ->  Read -> Buffer/Collector -> Trigger -> Append -> Measurements/graph

One last note:  The dt that I am changing is on an empty waveform that I append to my input signal in the upper left corner.

[Dennis_Knutson]

Duplicate: http://forums.ni.com/t5/LabVIEW/Virtual-Oscilloscope-Slow-Data-Acquisition-5-Hz-limit/m-p/2891640

Why the new post when you had it solved and why use the very incorrect acquisition method? 1 sample mode is just wrong and you were told that.

[Fievels]

He answered my question of why I could only sample up to a rate of 5 Hz.  But my program is still not functioning.  I wanted to try to make a new post that would outline my problems a little more coherently.

Changing the DAQ assistant to continous did not solve the issue.  Changing to DAQmx did not solve the problem, and I am not sure if it still one-sample.. but it was what was suggested to me last.  If you are reffering to the output.. it doesn't really matter where my signal comes from.  I have been testing it against a known 60-Hz.  (I didn't mean to include AO in this picture)

Thank you again.

[Dennis_Knutson]

You were clearly told to NOT use 1 sample mode and you marked that answer as solving your question. It simply makes no sense to go back to that mode. I don't think you understand the basics of data acquisition and ignoring the answers that you have been given without reason is inconsiderate.

[Fievels]

How do you move to continous mode with the DAQmx?  I tried adding a timer and changing the sample mode to continous,.. but the rate screws with the frequency and I get this message.

As for the output, it sais one-sample is my only option:

So.. It may be that I don't know what I'm doing.  but, that is why I am asking for help.

[Fievels]

I can assure everyone that I will be, and have been, attempting ALL solutions given to me.  This is important to me.

[Dennis_Knutson · Accepted solution]

Have you run any of the examples that come with LabVIEW? STOP using the 1 sample DAQmx Read. Right click on it and change the type. The other error would come if you changed the analog out task. Delete that part since you are not using it.

[Fievels]

Okay.. I understand why you are irritated with me now; I apologize.  Here is an update: 

[Fievels]

Okay, so this is where we are at:

input: 60Hz

dt: 120Hz

Read: Nsample Waveform

It looks like its almost fast enough.. but still choppy.

[Fievels]

!!!!  I have it working now.  

Continous mode, N Samples, extra high dt.  

I still get memory overflow, but I am really excited to get 60-Hz.  

Thank you for your help and patience Dennis.