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pre samples to impact in Labview 7.0

Hello,

I am doing impact testing and acquiring signals with 4472 boards.  I am using Labview 7.0.  When I acquire data triggered off the rising edge of my impact hammer, data collection starts as the rise of my stimulis signal begins, just after it begins actually.  I want to pad the impact signal with zeros before the impact spike.  I use the "trigger settings" cluster in "ni4472_Start Acquisition (N Boards).vi" to establish the trigger type and edge, but I don't see anything about pre samples.  I know a past student in my lab got presamples on 7.0 (with a very similar program to mine), but I can't figure it out.  Any help?
Tristan Ericson

Ohio State University Mechanical Engineering
Dynamics and Vibrations
201 West 19th Ave Suite N350
Columbus, OH 43210-1142

Office: 614-292-9029
Lab: 614-247-8077
Fax: 614-292-3163

"No one is useless in this world who lightens the burden of another." - Charles Dickens
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Hello Ericson,

It is likely that the other student used what is called a "reference trigger" which allows you to save both pre and post trigger samples.  It is difficult for me to say for sure though since I cannot find ni4472_Start Acquisition (N Samples).vi.  Can you please direct me to this program or post it if it is something that you created?  Thank you.

Regards,

Jeff Tipps
Applications Engineer
National Instruments

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Hello,

The file ni4472_Start Acquisition (N Boards).vi was found in a library: NI4472 example (N Boards - Single chassis).  The library was in a folder "example labview code" so I don't know where it came from.  I'm sure we didn't write it.  I've attached pictures that show this vi where triggering info is sent into it (It's the one that says "AI Start 4472" in the 1st picture).  This vi is on the third level, in the DAQ configuration file, which is in the main program (the main program is the background in both pictures below).

In the file ni4472_Start Acquisition (N Boards).vi, we found two inputs into suv-vi's that had pre-triggering inputs: "AI Start" and "Start Master 4472" (shown in the second picture).  I set both of these to 100, as shown in the picture, but when we ran the file and hit the hammer, no pre samples.  Please let me know if you have any more advice.

If you want me to post any of these files, I'd be glad to. (Just need to figure out how).

Thanks again,
Tristan



http://www.pbase.com/diamond2a/image/72857779/original.jpg



http://www.pbase.com/diamond2a/image/72858216/original.jpg



Tristan Ericson

Ohio State University Mechanical Engineering
Dynamics and Vibrations
201 West 19th Ave Suite N350
Columbus, OH 43210-1142

Office: 614-292-9029
Lab: 614-247-8077
Fax: 614-292-3163

"No one is useless in this world who lightens the burden of another." - Charles Dickens
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Tristan,

Can you post the code?

Thanks,

Abhinav T.
Applications Engineer
National Instruments
Abhinav T.
Applications Engineering
National Instruments India

LabVIEW Introduction Course - Six Hours
Getting Started with NI-DAQmx
Measurement Fundamentals
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Abhinav,

The .llb file in the following link should contain the main program and all the neccessary sub .vis if I understand the saving functionality of LabView,  if you find anything to be missing I'll be happy to upload it. 

http://s21.quicksharing.com/v/2887976/Idler_Impa...

Thanks


Tristan Ericson

Ohio State University Mechanical Engineering
Dynamics and Vibrations
201 West 19th Ave Suite N350
Columbus, OH 43210-1142

Office: 614-292-9029
Lab: 614-247-8077
Fax: 614-292-3163

"No one is useless in this world who lightens the burden of another." - Charles Dickens
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