11-29-2009 02:54 PM
I am trying to get displacement RMS value from a signal obtained from an accelerometer. This accelerometer is connected to a shaker that vibrates at 159,2 HZ with an acceleration RMS value of 3,16 m/s2. At that frequency it's supposed to obtain the same RMS value for velocity (3,16 mm/s) anf for displacement (3,16 um).
I have used the SVT RMS level.vi using the signal obtained from accelerometer as input. I obtain the correct aceleration RMS value. Then I double integrate that signal using SVT Intgration.vi and apply SVT RMS level.vi, but the value I obtain doesn't mach with the expected one(3,16 um).
Should I eliminate DC componet of the signal before integrating it? Or before using SVT RMS level?
11-30-2009 07:17 AM
Your expected values are valid only for a pure sine. Every little offset from the DAQ of amplifier will result in different values.
So you should eliminate the DC in your first measured signal. Your integration time should be a multiple of 1/159,2 s
PS: use 159,155 Hz 😉
PPS: If you want to do calibration take a look at SAM (Sinus approximation method)
11-30-2009 08:37 AM
Thank you for your answer!!!!
And how do I adjust integration time using SVL Integration.vi???
11-30-2009 10:51 AM
I have tried to take a look at SAM, but I couldn´t understand how would this method help in my issue.
Is this method implemented in Labview?
I would like another clue, because I am very interesed! Thanksssss!
12-01-2009 01:42 AM
Oiane wrote:Thank you for your answer!!!!
And how do I adjust integration time using SVL Integration.vi???
cut your data to a length of a multiple of the measured frequency.
12-01-2009 02:04 AM
The single tone measurements of LV work FFT based... I haven't found a SAM, I use the one my colleage wrote, so I can't provide it, sorry.
However SAM is a 3 to 4 parameter fit (4 if you also fit for the frequency) and LV provide the LS fit so .....