What is the output on the FFT PSD function?

I am trying to evaluate the FFT PSD function relative to frequency. I expect f(0) = the variance of all signals, but that is not what is given. Does anyone have any information about this. I ran a test array with a 1 Hz sin wave, with 10 samples/second, 120 total data points--the FFT PSD gives f(0)=0.

Hi,
The LabVIEW help file gives the following information concerning this function:
The FFT Power Spectral Density VI completes the following steps to compute power spectral density.
Computes the FFT of time signal.
Forms the power spectral density of time signal.
Averages the current power spectral density with the power spectral densities computed by the VI since the last time the averaging process was restarted.
Returns the averaged power spectral density in power spectral density
The single-channel version of this VI can perform single-channel measurements in both one-shot mode, meaning a single call, and continuous mode, meaning multiple calls with history. The single-channel version can perform multichannel measurements only in one-shot mode. If you want to make multichannel measurements in continuous mode, use the multichannel version of this VI.
The single-channel version of this VI maintains internal state information for a single channel only. Calling the single-channel version to process another channel without using the restart averaging control to clear the history results in an unexpected behavior of this VI. The unexpected behavior results from the VI passing the internal state information from one channel to another.
Note The single-channel version of this VI is primarily intended for continuous processing of a single channel. Do not generalize this behavior to the multichannel case and use the single-channel version in a For Loop to continuously process multiple channels by indexing an array of waveforms. Refer to the examples\measure\maxmpl.llb and the examples\analysis\measxmpl.llb for examples of how to use a multichannel version of a VI like the FFT Power Spectral Density VI in a loop.
Refer to the Noise Waveforms and PS Density VI in the labview\examples\measure\maxmpl.llb for an example of using the FFT Power Spectral Density VI.
Amanda Howard
Americas Services and Support Recruiting Manager
National Instruments

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What are the fft based algorithms DIAdem is using?

Greetings! I am relatively new to DIAdem and am trying to find some basic information about how DIAdem is performing some calculations, specifically the FFT based functions. The DIAdem help does not cover in depth what I would like to know and I cannot find anything on NI's website or these boards (yet) that does. I did find one post that discussed the algorithms used in DIAdem Crash Analysis (originating from the NHTSA?) that gave a very good discussion, but this is specific to Crash. Is there a similar paper for the algorithms within DIAdem? Yes, I have run the same data through both DIAdem and an app we currently use and the results are very close, but this anecdotal evidence is not enough to satisfy the folks I work for. Can someone point me in the correct direction? Thanks!

Hi,
DIAdem is using several different FFT algorithms, depending on the version of DIAdem and the mathematical function. The basic FFT, witch is calculating the real/imaginary part out of the time signal, is well defined. Each algorithm gives almost the same result. There are only very small differences on the last bits of the float values. The basic FFT algorithm is usually not very large. It is easy to use different functions or libraries depending on the needs. The results have to be the same in all cases.
DIAdem 10.2 is using a new algorithm which is able to do FFT calculations with any number of values, not just the power of two. This algorithm is also used in other NI-products like LabVIEW. A large afford is going into the quality and speed of this algorithm because not only the simple FFT but also a number of additional functions like the sound and vibration toolkit for LabVIEW is depending on this.
The difficult part, when it comes to comparison between DIAdem and other FFT calculations, is always the large number of options. You need to know the number of values, sampling frequency, window function, window correction and the averaging. You can calculate peak, rms or power spectrum and so on. Depending on the options, you can get very different but still correct results.
Crash is much more a question of standards. Starting with sampling frequencies and ending with precise defined algorithms to get a result like the HIC-value witch has to be reproducible and comparable between cars from different vendors all over the world.
As soon as you start to do real world FFT calculations there are so many options and possible ways do get the results you need, that it is impossible to discuss all of them in a documentation of a Software like DIAdem. You could write a series of books about this.
If you have specific questions about the FFT results, you can give it a try and ask on this forum.
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what are the Built-In-Functions in XSLT mapping?

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Dear Experts,
Briefly, could you explain what is the purpose or function of these tables:
1. INOB - link between internal number and object. Is internal number = internal order number? related to project? purpose?
2. AUSP - Characteristic values - what characteristics? all? purpose?
3. CABN - Characteristic : what is the purpose of this table?
4. KLAH - Class header data : what is purpose of Class ?
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Thanks in advance.
regards
Bass

1. INOB - link between internal number and object. Is internal number = internal order number? related to project? purpose?
It is a linking table for internal number and object for characterstics tables.It is not relate to project.
2. AUSP - Characteristic values - what characteristics? all? purpose?
It will show what are the objects in class and internal characterstics.Details it will not show and it shows only numbers
For e.gSuppose you have provided some values in Characterstics like qty 10,20..and colour ...red ,while..,Sytem will show these details in this table.
3. CABN - Characteristic : what is the purpose of this table?
It will show the type of characterstic is this numeric or character
4. KLAH - Class header data : what is purpose of Class ?
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What are the Includes in Function Module...? if the fuction group IS ZSJ_FC

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How can I access SAP through Internet....?
Moderator Message: Interview-like question(s). Thread locked.
Edited by: Suhas Saha on Sep 30, 2011 11:14 AM

Hi
No! U can insert an own you Z-INCLUDE or somethingelse, try to regenerate the index of the program.
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Hi,
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What is the table contains Function module include program name

Hi,
What is the table contains Function module include program name
Regards,
Raja

Try this FUNCTION_INCLUDE_INFO to get the include number to which function module belongs to.From this u ll get only the particular include name.
or
if u need the all the includes used in the function group u have use INNER JOIN on TFDIR and D010INC table
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I hope this will help u.
Thanks & Regards
Santhosh
Message was edited by:
santhosh ds

What are the responsibilities of Functional consultant in Upgradation?

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What are the responsibilities of Functional consultant in an Upgradation Project
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Thanks
regards
Krishna

Krishna,
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Cheers!!!
NMK
Please give the point for the useful reply.

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What is the output on the FFT PSD function?

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