Unwanted delay when using DAQ in Labview

[BirgerBrosa]

Hello again NI. I have a problem.

In Labview, I have constructed the "circuit" seen in the picture (file below).

The signal generator goes into a DAQ-board, and back into a graph in Labview.

However, if I try to adjust things about the signal, such as the amplitude, or frequency, or offset, there is a delay of about 5-10 seconds before I see any change on the graph.

This is very unwanted, and I therefore wanted to know if there is any way I can diminish the delay, or maybe completely remove it?

I hope someone can help me.

[crossrulz]

You will have to attach your VI so we can see what your settings are in those Express VIs (DAQ Assistants and Simulate Signal).  But my thought is that at least one of those is taking the 5-10 seconds, preventing your loop from iterating and stopping the update.

[BirgerBrosa]

My bad. Here is my VI.

[GerdW]

Hi Brosa,

as far as I can see all ExpressVIs should execute in 100ms.

Try this:

Move the DAQAssistent reading the input signal with the chart into its own loop.

Add another chart after the SimulateSignal ExpressVI to verify the waveform creation part.

Run both loops in parallel.

How is AO0 and AI0 connected?

Btw. learning DAQmx is simple by reading this and examining the example VIs coming with LabVIEW!

[BirgerBrosa]

Hi there.

I am a bit unsure of what you wanted me to do with the loops. Here is how I understood it (look at file).

Have I done what you suggested?

Also, for your second question, AO0 and AI0 is physically connected on the Data acquisition board through a BNC-cabel.

[GerdW]

Hi Brosa,

nearly complete: just add one more chart and connect with the signal coming from SimulateSignal ExpressVI…

(And use AutoCleanup.)

[BirgerBrosa]

Okay, I've done what you suggested.

I can see that the chart (or graph) connected directly to the simulation signal is immediately changing when I change the offset, frequency etc.

However, the graph connected to the DAQ still has a big delay time , and I really don't want that 😞

Is there anything else I can do?

[GerdW]

Hi Brosa,

you changed the DAQAssistent reading the AI signal from reading 100 samples to 1k samples: now it takes 1s to display new data instead of just 100ms…

[aeastet]

Are you going directly from the analog out to the analog in? Is there something in between the analog out and analog in?

[aeastet]

I also noticed that your signal output is send 100 samples and your DAQ Assistant2 is send 500 samples. You should make those the same.