Integrating Acceleration (Simulated) to Velocity

[bilalskd]

Hey,

I am relatively inexperienced in LabView. I am trying to integrate a simulated sine wave to get a cosine wave. I am considering this sine wave as a form of acceleration (hypothetical)  by scaling it using the voltage to EU vi available in the Sound and Vibration Toolkit. After scaling I am getting the hypothetical acceleration in g units which I am then integrating to velocity using the 'SVL Integration vi'. Now I should be getting 90 degree phase shifted signal at the output (cosine wave) right?

The issue is that when my sine wave signal is generated with the reset signal parameter being true it's not giving me the exact cosine output. But when the reset signal is false I am accurately getting the exact 90 degree shifted wave. Why is this happening can someone explain this to me? 

I have attached the images and the VI below,
Thank You.

 

[Bob_Schor]

I've never installed nor used the Sound and Vibration Toolkit.  But integrating a Sine wave in LabVIEW and have it produce a Cosine Wave is very simple, and even works.  Here's a Snippet, and the result:

After dividing by 2 pi f, the peak of the Cosine wave (red) lags (as it should) the peak of the Sine Wave (white) by 90 degrees.

Bob Schor

[bilalskd]

Thank you for that.

This is me just experimenting with integration. 

My main goal will be to integrate an acquired acceleration ( which will not be a simple sine wave) to velocity. 

I would love if anyone has more information regarding these VI of the Sound and Vibration toolkit. 

[doldonics]

[Deleted by author]

[Bob_Schor]

[A colleague used my computer to get a Quote from NI.  I didn't notice that in doing so, my logon to the Forum wasn't "mine".  I apologize for the confusion, and have copied my "real" post below]

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What are you doing that requires specifically the Sound and Vibration Toolkit?  Note that my simple demo didn't use it (I've never installed it, so I don't really know what "extra" functionality it provides.  Are you applying A, B, or C weighting filters on a time-domain signal?  [I'm not sure I even know what that means!]  of sound sources?  Are you doing Octave Analysis?

Have you looked at the Frequency Analysis tools that ship with LabVIEW, including FFTs and other transforms, Filtering, etc.?  Make sure you understand the Basic Tools already in LabVIEW before you "specialize".

Bob Schor

[dsb@NI · Accepted solution]

The Sound and Vibration Toolkit offers two methods for integrating vibration signals. 
SVL Integration (1 Ch) VI and SVL Integration (N Ch) VI use filters to remove the DC component and apply the 1 / (2pi*f). These VIs are documented here:
SVL Integration VI - NI
Integration - NI

The SVL Integration VI is polymorphic:

and also includes instances:
SVL Single Block Integration (1 Ch)

SVL Single Block Integration (N Ch) 

which use numerical integration (similar to that implemented by Bob). Dig into the code to compare the implementations.

Recommendations:
 - Use filter-based methods to process continuously acquired vibration data.
 - Use numerical methods to process a finite duration of vibration data and you want to set initial/final conditions on the integrated signal.

[dsb@NI]

The benefit of using the Sound and Vibration Toolkit is that (even for relatively simple operations such as time integration) the algorithms have been reviewed, unit tested, and field tested. 

Sometimes, the nuances of a measurement are more difficult than the initial academic case. For instance, integration of vibration signals is extremely sensitive to DC components. Even with AC coupling enabled on DSA input devices, we found that tiny DC components integrated such that the vibrations around equilibrium looked like they were wandering farther and farther from equilibrium. On the other hand, filter-based approaches never settled fast enough for real-world impacts nor explosions. 

I wholeheartedly endorse Bob's message of understanding your LabVIEW tools before specializing. I also posit that you should understand what (specialized) tools are available before developing custom tools.