Position Vs Time for LVDT

[JCollado]

Hello  I'm very new to Labview (Three weeks)  Can anyone give me some sample on how to measure position vs time for LVDT? This is very simple using an Oscilloscope by position X1 and X2 cursors to measure delta time but I am not sure how to do this with the labview graphs or charts. I want measure time from trigger to fist sign of movement, total stroke time and snubbing time (Of actuator). I have attached an image of what I want to measure. Are there specific VIs to look for these times. Even by manually placing cursors on desired position in labview all I get is the time for each cursor but not the delta time between cursors. 

Any help will be greatly appreciated

Juan 

[JCollado]

I just want to clarify that I wish to display the different times on digital displays automatically fo the user. I will then save these values to a database.

Just looking to speed it up for the technician by getting rid of the oscilloscope.

[George_P_Burdell]

JCollado-

When using a waveform graph, rt click on the grey part and go to Visible Items.  Make sure Graph Palette and Cursor Legend are checked.  From there, you can create new cursors by rt clicking in the Cursor window and select Create Cursor.  You can create multiple cursors and view the values of each point.  Then you can simply subtract these values.  This can be setup programmatically by using property nodes. 

[JCollado]

Hello Mike

Thanks for your reply.

Yes at design time I was able to setup the cursors and then I displayed them on digital controls through property nodes and subtracting the difference of the two cursors (X1-X2).(This is in a while loop)

I really would like to do this automatically.

I want to more or less have an array and functions that looks for changes in the value of Y and measure time from trigger to that point or from that point to the next change in Y.

It may be possible in awhile loop and checking for changes in Y and that should be an indication that the position speed shifted of sped up.

I was wondering if there were any functions that automatically detects changes in low peaks and high peaks.

Again I would like to disply  delay time, full stroke time, snubbing time automatically without the technician moving the cursors themselves.

Thanks

JCollado

[aeastet]

Do you have some sample data?

[JCollado]

I am waiting on my hardware and right now all I have is simulated devices. Maybe I will simulate it with an array for you.

The data will look similar to the image attached. I will upload my data and source code as soon as I have some samples.

I thoughtsome other people would be working with similar projects such as hydraulic servos systems.

Thanks

[George_P_Burdell]

JCollado-

You may be able to do this with Event Structures to detect changes of your cursor.  Since you are a new user, please take a look at the links below for more information on Event Structures and their capabilities. 

LabVIEW 2009 Help: Event Structure
NI Developer Zone: Event-Driven Programming in LabVIEW

[JCollado]

Thanks for your help.

I have attached the VI I'm working on. It is working manually as far as the graph time measurement. No database connection and other controls not in use yet.

I am also thinking that I might be able to do this with the shift register checking if current value for Y is higher then last. If higher I should take trigger time to this time and so on.

It will take me a bit because I'm so new to labview and new to Instrumentation type programming.

Thanks

[aeastet]

I made a VI that generates data since I did not have data to work with. If you take the second derivative of the data you can easily ge the points that you need. Take a look at the example. It is not pretty but it gets the job done.

[aeastet]

Set the peak Limit control to .0002. I should have save it as the default value but I forgot.