Comments on: Amplitude And Energy Correction – A Brief Summary http://blog.prosig.com/2009/09/01/amplitude-and-energy-correction-a-brief-summary/ Telling you what you need to know about noise & vibration Tue, 07 Feb 2012 15:32:30 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: John Matheyhttp://blog.prosig.com/2009/09/01/amplitude-and-energy-correction-a-brief-summary/comment-page-1/#comment-15582 John Mathey Fri, 06 May 2011 12:27:50 +0000 http://blog.prosig.com/?p=266#comment-15582 Matthieu, Calculating the RSS is simply a vector sum of the 3 orthogonal components s, y, & z.. In mathematical terminology it is x^2 + y^2 + z^2. Typically this is done on the RMS levels or amplitudes of the signals and not the raw time signals as the calculation includes squaring of the signals which will loose the phase relationship of the raw time signals. The RSS can be calculated using the Auto Power spectra or Power Spectral Density or any other RMS levels calculated (single numbers, order cuts, etc) for the x, y, and z signals giving a single spectrum.The PROSIG software provides a module for performing this calculation on data curves (RMS vs time, RMS vs. frequency, etc....) . This module is call CALCRESULTANT and can be found in two places in the analysis menu or side panel underCrash Biomechanics Calculate x,y,z ResultantorHuman Biodynamics Human Body Vibration Calculate x,y,z ResultantThis module also allows for individual weighting of the signals if one or more of the 3 directions are of more importance in your calculations.I hope this feedback is helpful. If you have additional questions, please feel free to contact me.John Mathey Technical Support PROSIG-USA john.mathey@prosig.com Matthieu,
Calculating the RSS is simply a vector sum of the 3 orthogonal components s, y, & z.. In mathematical terminology it is x^2 + y^2 + z^2. Typically this is done on the RMS levels or amplitudes of the signals and not the raw time signals as the calculation includes squaring of the signals which will loose the phase relationship of the raw time signals. The RSS can be calculated using the Auto Power spectra or Power Spectral Density or any other RMS levels calculated (single numbers, order cuts, etc) for the x, y, and z signals giving a single spectrum.

The PROSIG software provides a module for performing this calculation on data curves (RMS vs time, RMS vs. frequency, etc….) . This module is call CALCRESULTANT and can be found in two places in the analysis menu or side panel under

Crash Biomechanics Calculate x,y,z Resultant

or

Human Biodynamics
Human Body Vibration Calculate x,y,z Resultant

This module also allows for individual weighting of the signals if one or more of the 3 directions are of more importance in your calculations.

I hope this feedback is helpful. If you have additional questions, please feel free to contact me.

John Mathey
Technical Support
PROSIG-USA
john.mathey@prosig.com

]]> By: Matthieu Tessierhttp://blog.prosig.com/2009/09/01/amplitude-and-energy-correction-a-brief-summary/comment-page-1/#comment-14657 Matthieu Tessier Fri, 25 Feb 2011 15:16:17 +0000 http://blog.prosig.com/?p=266#comment-14657 Hello, As part of a vibration measurement campaign, I'm being asked to provide acceleration levels. vibration spectrum and "complex of loads acting on a component (x,y,z)". The last item is not really clear to me. I've previously heard of RSS values to obtain a single spectrum from a tri-axial vibration measurement. How do I need to process my raw vibration data to obtain a RSS spectrum? If anyone has an idea, please let me know. Thanks and regards, Matthieu Hello,
As part of a vibration measurement campaign, I’m being asked to provide acceleration levels. vibration spectrum and “complex of loads acting on a component (x,y,z)”.
The last item is not really clear to me.
I’ve previously heard of RSS values to obtain a single spectrum from a tri-axial vibration measurement.
How do I need to process my raw vibration data to obtain a RSS spectrum?
If anyone has an idea, please let me know.
Thanks and regards,
Matthieu

]]> By: John Matheyhttp://blog.prosig.com/2009/09/01/amplitude-and-energy-correction-a-brief-summary/comment-page-1/#comment-771 John Mathey Wed, 21 Apr 2010 11:43:20 +0000 http://blog.prosig.com/?p=266#comment-771 Thank you for your comment to the blog.The answer to your question depends on what information you are looking for from the strain gage.If you need know the static strain, then the strain gage sensor should be zeroed out prior to putting the component under load, then the DC offset value will be the component's loaded static strain. The dynamic (vibratory) strain will be superimposed on the DC signal level. You might find the DC level will use up much of the dynamic range of the measuring instrumentation not permitting optimized gain settings for the dynamic signal.If you are only looking for the dynamic strain due to vibration, then you can remove the DC offset value from the strain gage sensor signal. This will allow the channel gain setting to be increased to optimal levels for the dynamic signal.I hope this response adequately addresses your question. Please feel free to contact me directly if you have additional questions.John Mathey PROSIG-USA john.mathey@prosig.com Thank you for your comment to the blog.

The answer to your question depends on what information you are looking for from the strain gage.

If you need know the static strain, then the strain gage sensor should be zeroed out prior to putting the component under load, then the DC offset value will be the component’s loaded static strain. The dynamic (vibratory) strain will be superimposed on the DC signal level. You might find the DC level will use up much of the dynamic range of the measuring instrumentation not permitting optimized gain settings for the dynamic signal.

If you are only looking for the dynamic strain due to vibration, then you can remove the DC offset value from the strain gage sensor signal. This will allow the channel gain setting to be increased to optimal levels for the dynamic signal.

I hope this response adequately addresses your question. Please feel free to contact me directly if you have additional questions.

John Mathey
PROSIG-USA
john.mathey@prosig.com

]]> By: Eapenhttp://blog.prosig.com/2009/09/01/amplitude-and-energy-correction-a-brief-summary/comment-page-1/#comment-758 Eapen Mon, 19 Apr 2010 16:51:27 +0000 http://blog.prosig.com/?p=266#comment-758 i have got some readings from a strain gage sensor,now should i remove the DC offset value to get the proper values or shoulldnt i... i have got some readings from a strain gage sensor,now should i remove the DC offset value to get the proper values or shoulldnt i…

]]> By: Gareth Edwardshttp://blog.prosig.com/2009/09/01/amplitude-and-energy-correction-a-brief-summary/comment-page-1/#comment-727 Gareth Edwards Wed, 14 Apr 2010 13:33:21 +0000 http://blog.prosig.com/?p=266#comment-727 John,Good explanation for the ideal sinusoidal case. A couple of comments:Equation 2 is incorrect - sqrt(1.5) = 1.2247...VrmsIt would be good to expand on this subject to include how to evaluate sinusoidal Vrms signals that are not located on a discrete spectral frequency. Or include the general version of Equation 6 which is the squared "area under the curve" as opposed to the sum of discrete spectral components John,

Good explanation for the ideal sinusoidal case. A couple of comments:

Equation 2 is incorrect – sqrt(1.5) = 1.2247…Vrms

It would be good to expand on this subject to include how to evaluate sinusoidal Vrms signals that are not located on a discrete spectral frequency. Or include the general version of Equation 6 which is the squared “area under the curve” as opposed to the sum of discrete spectral components

]]> By: Chris Masonhttp://blog.prosig.com/2009/09/01/amplitude-and-energy-correction-a-brief-summary/comment-page-1/#comment-620 Chris Mason Mon, 02 Nov 2009 11:08:31 +0000 http://blog.prosig.com/?p=266#comment-620 Hi EmmaI expect you've already had a look around the rest of the blog, but there are a couple of other posts that might help.There is the article <a href="http://blog.prosig.com/2003/07/29/notes-on-fourier-analysis/" rel="nofollow">Notes On Fourier Analysis</a> by Dr Mercer. This has some good illustrated examples and also looks at the mathematics behind the Fourier Transform.Also, you may find <a href="http://blog.prosig.com/2009/04/22/10-great-fourier-transform-links/" rel="nofollow">10 Great Fourier Transform Links</a> helpful. This collects together several good WWW resources. One of the best links there is a series of lectures by Professor Brad Osgood of Stanford University. There are about 30 hour long lectures, but maybe the first few will help you.Anyway, good luck with your thesis. If you have any specific questions then feel free to post a comment somewhere on the blog and one of our posters may be able to help. Hi Emma

I expect you’ve already had a look around the rest of the blog, but there are a couple of other posts that might help.

There is the article Notes On Fourier Analysis by Dr Mercer. This has some good illustrated examples and also looks at the mathematics behind the Fourier Transform.

Also, you may find 10 Great Fourier Transform Links helpful. This collects together several good WWW resources. One of the best links there is a series of lectures by Professor Brad Osgood of Stanford University. There are about 30 hour long lectures, but maybe the first few will help you.

Anyway, good luck with your thesis. If you have any specific questions then feel free to post a comment somewhere on the blog and one of our posters may be able to help.

]]> By: Emma Dalyhttp://blog.prosig.com/2009/09/01/amplitude-and-energy-correction-a-brief-summary/comment-page-1/#comment-619 Emma Daly Sun, 01 Nov 2009 14:30:42 +0000 http://blog.prosig.com/?p=266#comment-619 Hi, JohnI am a final year engineering student and I am doing my thesis on damage detection using distributed accelerometer. In this I will be using the Fast fourier transforms and know very little about the topic. Is there any chance you have any information that will help me understand the basic? Any help at all would be greatly appreciated.Emma Hi, John

I am a final year engineering student and I am doing my thesis on damage detection using distributed accelerometer. In this I will be using the Fast fourier transforms and know very little about the topic. Is there any chance you have any information that will help me understand the basic? Any help at all would be greatly appreciated.

Emma

]]> By: Yevgeni Tunikhttp://blog.prosig.com/2009/09/01/amplitude-and-energy-correction-a-brief-summary/comment-page-1/#comment-618 Yevgeni Tunik Mon, 19 Oct 2009 07:36:09 +0000 http://blog.prosig.com/?p=266#comment-618 The text in the pictures is almost unreadable. The text in the pictures is almost unreadable.

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