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Subject Repeatable measurements? Date
Wed Dec 18 2002 02:16
Author Lars Morset
(morset@winmls.com)
Dear Werner, interesting question, thanks! First of all, the impulse response in itself is reliable if the system you are measuring (in this case a wood bar) is
1. Time invariant - not changing as a function of time. 2. Linear - if you double the amplitude of your input signal the output amplitude is also doubled and superposition is valid.
A wooden bar will in this case be according to these requirements and therefore the impulse response is valid.
The reason you do not get repeatable measurements is probably because when you hit it, you are not able to reproduce the hit (e.g. the direction). Please see a table that gives the repeatability on page 2 of the article ISMA2001_MorsetArticleFinal.doc found at http://www.nvo.com/winmls/nss-folder/articles
Reproducability should be discussed in the article above, please let me know if you have further questions.
For your setup, hanging the bar, I would recommend that you use our magnet-coil system to get a reliable excitation. The way the bar is suspended is also important, you can experiment by changing the suspension and see what effect this has.
