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Lysworld

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I am studying Sports Science and researching the use of an accelerometer during specific wieght training type movements. I have a MEMS device (unfortunately I only have mininal details regarding it) which can measure upto 24G and 400Hz and comes with basic software that transfers the data into an excel file.

My questions are as follows:

1. How do I convert the acceleration from G to m/s/s? (I am aware that 1G is technically 9.81, however, I would like to know the 'real-time acceleration' i.e. as the bar is moving - in that as it is stationary this value would be 0m/s/s)

2. How can I integrate this data into velocity and then displacement? (I am aware this may cause an exaggeration of error if done in the time domain - FFT? - and that data needs to be converted to the frequency domain. Is this correct?)

I am looking for any advice/direction to necessary reading that will help me and if possible any example excel files.

I have seen the following thread before: https://www.physicsforums.com/archive/index.php/t-123128.html although I am a novice to this and only have a vague idea of how to do any of the instructions given

1. Remove the mean from your sample (now have zero-mean sample)

2. Integrate once to get velocity using some rule (trapezoidal, etc.)

3. Remove the mean from the velocity

4. Integrate again to get displacement.

5. Remove the mean. Note, if you plot this, you will see drift over time.

6. To eliminate (some to most) of the drift (trend), use a least squares fit (high degree depending on data) to determine polynomial coefficients.

7. Remove the least squares polynomial function from your data.

Also, am I correct in thinking the trapezoidal rule is not appropriate for non-constant acceleration data?

3. Is it essential to run a filter on the data before these transformations? (Would this be a low-pass or Kalman - again, any advice or direction would be hugely appreciated)

Thanks for reading