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Acceleration to displacement problems

Anyone got any idea why my displacement graphs are telling me there is a maximum displacement in the tens of meters? The sample was securely fixed and would not have moved anywhere near a metre.

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Message 11 of 14
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Hello again, 

 

My overall objective is to produce a logical displacement curve from the acceleration data attached. Previously there was a lot of noise and useless data which I think was leading to weird and non-sensical displacement and velocity graphs. I have now tried to cut down the data to the main impact event in excel. I now want to reimport the excel data and produce the displacement data. 

 

I've tried to make a start at the importing of the excel sheet using the read delimited spreadsheet Vi, but I'm a total beginner and don't know where to go from there.  

 

If anyone can help, thank you!

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Message 12 of 14
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Hard words: garbage in -> garbage out

 

the measured acceleration is mainly positive -> integral (velocity) mainly increases-> integral (displacement) increases

see post from GerdW.

Even a sligth bias removement  (usually done with a highpass filter) wouldn't help.

In your first post you posted the expected wfrms. The point of investigation would have been while monitoring the test and not getting the expected results.... 

A possible (not so rare) source of error could be  loose contacts at the accelerometer connector .. this results in short positive peaks ( positive slew rate is a function of supply current (4mA) and cable capacity, neg. slewrate much faster) ... If this happens at negative accelerations (also plausible)  you could end up with such signals.  Since the open cable detection works by detecting the crossing of a voltage in the 19V to 22V region and your loose contacts are short, this only can be seen in the signal... but would have needed a higher samplerate or a scope ...

 

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


Message 13 of 14
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Did you even try to run your code?  I ran only the Read Delimited Spreadsheet part, it asked me for a file, I gave it the downloaded "integration test.txt" file you posted (thank you), and got this:

Integration Plot.png

Isn't this what you want?  I assume you know how to use LabVIEW's Help feature to learn about the Delimited Spreadsheet functions, and to know you can also wire a path to the input if you don't want it to ask you "What do you want to read?".

 

Bob Schor

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Message 14 of 14
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