Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

PSD (Power Spectral Density) Interpertation/Understanding

Status
Not open for further replies.
struclearner

struclearner

Structural
Joined
May 8, 2010
Messages
122
Location
US
Dears,
I need help to understand PSD values interpretation.
When a PSD is created from acceleration values of a Time domain data from a random vibration scenario.
The acceleration values might occur more than once, or the data values might fall within a certain range/width of values.
A Histogram of the data will show the frequency content of the values.
A PSD will convert the Time domain data (acceleration) values to frequency domain data ((accelerationRMS)^2/Hz) values.
What the PSD data tell us?
Does PSD tells that Ordinate (y-axis) value occurrence is this many times, which is the frequency value on the abscissa (x-axis).
Can the PSD values be calculated from a Histogram of the Time domain data?

Thank you very much for your help of explanation and insight.
 
Sort by date Sort by votes
The PSD is the square of the Fourier transform of the time domain data, so no, you cannot get it from a histogram.

I suggest you read up on Fourier transforms.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
Upvote 0 Downvote
I agree with IRstuff.

A histogram tabulates values into bins/categories, and you might loosely call the number of items in a given bin the "frequency" of occurrence of that value range.
But that type of "frequency" has absolutely nothing to do with the type of frequency studied in fourier analysis or psd analysis.

Does PSD tells that Ordinate (y-axis) value occurrence is this many times, which is the frequency value on the abscissa (x-axis).
Click to expand...
No.
Can the PSD values be calculated from a Histogram of the Time domain data?
Click to expand...
No.
What the PSD data tell us?
Click to expand...
I think it deserves a bit of googling on your part to get an idea of the complexity of the topic and various definitions and applications of PSD.
I don't work with it much (work with FFT's a lot more). My two cents is that PSD is typically useful for studying and characterizing random signals, whereas as fft are more often more useful for periodic signals.






=====================================
(2B)+(2B)' ?
 
Upvote 0 Downvote
Upvote 0 Downvote
The only thing of note is energy is conserved across the Fourier transform, which is a good thing, so the integral of the PSD results in the total power of the measurand.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
Upvote 0 Downvote
struclearner

when dealing with "discrete" time series data, you use discrete transforms. They work the same way as traditional PSD methods, but with discrete time series data.

Electronic measurements use this too, as the data is digitized.

 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

sarclee
  • Locked
  • Question Question
PSD Output Envelope
Replies
3
Views
555
sarclee
sarclee
H.A. Camp
  • Locked
  • Question Question
(Mis)Understanding How My SPL Meter Sums Spectral Amplitudes
Replies
8
Views
630
GregLocock
GregLocock
BioMes
  • Locked
  • Question Question
Understanding complex input and output in frequency response FEA
Replies
9
Views
1K
BioMes
BioMes
struclearner
  • Locked
  • Question Question
Book to Understand PSD and FFT for Time Domain Data to Frequency Domain Conversion!
Replies
2
Views
502
electricpete
electricpete
CamJPete
  • Locked
  • Question Question
How to add spectral amplitude values in a band
Replies
2
Views
405
CamJPete
CamJPete

Part and Inventory Search

Sponsor

Back
Top