Integrating Acceleration

[Durbin]

I am having difficulty figuring how to implement integrals of acceleration to displacement into my script. I need to add the function of calculating the displacement for each axis from a tri-accelerometer with x-axis being frequency. I currently have a script that can apply FFT to the raw data and graph the acceleration against frequency. When I just integrate the acceleration, the values go off to infinite. I think im missing the unknown constants and boundary conditions to the integrals when going from acceleration to displacement but im not sure on how to add that.

Can someone help me go from acceleration to displacement correctly using vbs script?  

[müller+krahmer]

Script and data would be helpful to see what goes wrong.

[Durbin]

Holger, I have two data acquisition systems and with one I can convert it to displacement, but the post processing of that system is held within. Attached is picture showing results from system 1 outputting the raw data into displacement. I am currently trying to solve for just one direction of the tri-accelerometer on Diadem which is how I post process data for the second data acquisition system. Attached is the script where I convert the raw data which is in g to m/s^2. Then I double integrate and apply a FFT to it. The attached raw data is exported from the first system which outputted the attached graph in hopes of finding a way in diadem to get displacement correct. 

Any feedback is appreciated. 

[müller+krahmer]

Checked your data and script and found no obvious error, but also no similarities between data of the two systems. Are both datasets from the same test?

[Durbin]

Yes, the datasets are from the exact same test. The graph from the first system is the data already processed into displacement. I took the raw data that was used to make that graph and put it into an excel sheet to try and replicate with Diadem.