The correct filter frequency depends on the total duration, as well as on the duration of the two ramps and the plateau.
Generate the idealized pulse on your computer using Matlab or some other software program. Then perform a Fourier transform on the pulse. This will give you the pulse's frequency content. The pulse will probably have a roll-off at higher frequencies. Then use "engineering judgment" to choose a maximum frequency of interest.
Next, set the sample rate at least ten times greater than the maximum frequency of interest. This is a "rule-of-thumb" for time domain calculations per the IEST Handbook for Dynamic Data Acquisition.
Finally, choose the lowpass frequency. The purpose of this filtering is for anti-aliasing, as well as to eliminate spurious noise. This filtering should be performed on the analog signal prior to digitization. The IEST Handbook has guidelines for selecting the proper filter.
Here is the Handbook reference:
IEST-RD-DTE012.2: HANDBOOK FOR DYNAMIC DATA ACQUISITION AND ANALYSIS
Published 9/27/2006
ISBN: 978-0-9787868-0-9
Document Number: D012
Number of Pages: 321
It is available from: http://www.iest.org/
Tom Irvine
http://www.vibrationdata.com
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