Integrating accelerometer data in DasyLab using DT9837

[Generic Goat]

Hello,

I have tried to collect acceleration, velocity, and displacement data from accelerometer raw signals. I lose lots of data in the process. Even if i input a sin wave from a signal generator, the integration chops the aplitude down by orders of magnitude each time. What am I doing wrong? I am also having troubles with the integrated signals drifting very fast - the 'restart calculation' integration option works o.k; is there anything else I can do to obtain accurate signals? Or am i better off post processing the raw acceleration data in MATALB or something with more robust solvers?

 

Thank you

[DAQman]

I've used DASYLab to collect displacement data, but instead of integrating the raw data, I performed the integration with the FFT module. Here's a simple worksheet (attachment). First, it injects a 50Hz sine wave fed into the Data Window module, which is necessary for a good FFT. You can find internet windowing information by using the search phrase "fft windowing types." After the Data Window, the FFT generates an amplitude-optimized FFT and does a double integration for displacement. The next step is to transform the acceleration data to mils (A mil is a thousandth of an inch — .001 inch) by multiplying it by 386,000 ft/s/s. It then extracts the maximum value and the position of that value to produce results of 3.91 mils at 50Hz. Years ago, I could do the math to show that a 1-volt p-p 50Hz sine wave has a displacement of 50Hz but not today. I'll leave that up to you.

FFT_TEST.DSB

[DAQman]

According to DASYLab Help, Integration is finding the area under the curve using the following formula:

Dist = (1 / sample rate), which explains the small amplitude.

[Fausto]

Hello @Generic Goat.

Please reply with your DASYLab worksheet and screen captures of the displays in DASYLab showing the issue(s).

Regards,

Fausto

[Generic Goat]

 

on the signal generator, I am inputting a 1hz sine wave with 1v amplitude. I am expecting a -cos waveform with similar amplitude. However, I am getting an amplitude that is much smaller than what I was expecting. There is also some detrending needed. What do you recommend? 

 

[Fausto]

Please reply with your worksheet and screen captures of each module's configuration.

[Generic Goat]

 

 

Integrate block 1 and 2 are the same.

 

 

DEFNAME.DSB

[Generic Goat]

 This works great. integrating twice... 

386,000∫∫1 sin(2*pi*50 t)dt

yields 3.9mils at 50hz according to Wolfram! 

Thank you.

[FrancoC]

If I want to plot the displacement data in a Chart Recorder, is it possible to do so if I use the FFT Module for integration? If not, what are some other options? Thanks.

[FrancoC]

If I want to plot the displacement data in a Chart Recorder, is it possible to do so if I use the FFT Module for integration? If not, what are some other options? Thanks.