FFT Integration VS. Integration Module

[signal1]

I'm getting very different results integration inside the FFT module vs. the standard differentiation/integration module and I need to know why.

I want to get position and velocity from acceleration input. 

One method of using this is to use the integration filter built into the FFT module which converts to frequencies and integrates the results in one module.  Another method is to use the FFT module to convert the vibration data into the frequency spectrum and then in a separate module integrate the spectrum. 

To my way of thinking, these two ways should give the same result.  They don't.  Example programs are attached, your opinions would be appreciated. 

In addition to the internal/external integration issue other questions are:

- What is the best window (i.e. Hanning?) for transient acceleration data? 

- Can block size (for example in the Differentail module ("Restart after "n" blocks") or the Statistical module) affect the results?  Note the needed bandwith is from 2 to 1 kHz. 

Thanks very much,

Bob

For the attachments, the individual integration module (separate from the FFT module) is "INDIV INT MODULE 00.DSB" .  When integration is done inside the FFT module it is called "INT IN FFT MODULE.DSB". 

Since DSB files are not allowed in this post these files have been zipped. 

[Laura F.]

Hello Bob,

This question would be better answered on the DASYLab forums.  The NI DASYLab forum has to do more with using our hardware with DASYLab.  The first link on the DASYLab forum page is for general DASYLab questions and I would recommend re-posting your question there.

Sorry I can't be of more help!

Regards,
Laura

[Brejesh]

Sorry! i didn't get new thread for this topic, so i am replying.......

I earlier used Dasylab for acquiring data from Accelerometer.Getting Accelration Vs Frequency and Time charts.

Now i want to use Strain gage for Torque measurement.

My applications includ measuring Torque on Tensile bar and on Rotating shaft aswell.

My question is ? I see Strain(Deflection) directly after connecting A/D module with digital meter.But if i want to measure Torque. Is it possible to get. If so i need to analyse Torque Vs Angle.

Please post suggestions

[dnlwthrn]

It sounds to me like you need to calibrate the part that you have strain-gaged.  Most apps that I've done like this have involved two parts:  strain gaging and the instrumentation to measure strain, and then running a cal by applying a known torque to the part and recording the strain levels for the torque.  Easy way to do this is with a lever arm of known length and cast weights.  Of course, if you're trying to measure running torque its a different story...

Hope this helps!