Area for a fixed number of triggered samples

[geo2342]

Hello All

I am a newbie here so have some patience. Basically I have two signals that using lab view express VI's i have been able separate and trigger. The output from each trigger is a 200 sample section of signal that I am interested in. For simplicity the curve is a vertical line up to about 2 volts that then curves to about 2.5 volts over about .25 to .5 seconds followed by a vertical drop back down to 0 volts (See Below).


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I would like to compute the area under this curve(for the 200 sample triggered sections) however with the Integral VI I am having some difficulty. How the heck do i set it up to do this for these 200 sample sections? Is there a VI that integrates based on samples?

[PauloM]

Hello,

Did you try integrate x(t).vi under Analyse...Signal Processing...Time domain?

Hope it helps,
Paulo

[geo2342]

Paulo,

Orginally i searched for the VI using the search function in the pallet and integrate and this gave me i think the basic VI which i could not seem to configure. I followed what you said and it gave me what I think is the express time domain VI which can be configured for integrating or other calculus.

This actually worked. I have the results in a table and the final value appears to match my rough hand calculation for the area.

I just want the final result of the area out of the output. What is an easy way to get this? It seems to spit out the result of each calculation that the integration does.

Thanks

George

[PauloM]

Hello George,

If I understood well your request, I think you need the last value of your integration array, so you can do an index array (in the array palette) where the index element is the array size (also in the array palette). This should give you the area of the entire signal.

Hope this helps,
Paulo

[Brett_B.]

geo,

The Numeric Integration.vi takes an array as an input and returns the final value. I think this is the best function to use. It also allows you to choose the integration method. This VI is very easy to use.

hope this helps,
-Brett

[geo2342]

Paulo,

I actually found an express VI that if i remeber right is called extract segment. It does the same thing I belive as the index array fuction that you mentioned. I have difficulty with the regular functions like the array one you mentioned. They are not intuitive to wire up properly. The express VI's are so easy. You just put a wire in and a wire out and double click on it to configure. I am just having a lot of trouble in some cases finding the right one.

George

[geo2342]

Paulo,

I actually found an express VI that if i remeber right is called extract segment. It does the same thing I belive as the index array fuction that you mentioned. I have difficulty with the regular functions like the array one you mentioned. They are not intuitive to wire up properly. The express VI's are so easy. You just put a wire in and a wire out and double click on it to configure. I am just having a lot of trouble in some cases finding the right one.

George

[PauloM]

Hello George,

You can use the numeric integration proposed by Bret.
But if you want to see how it is done with the "normal functions" (I'm not very good with the express...) in the attached vi there is an example of how to get the last value of an array.

Regards,
Paulo