How to do FFT of vibrations signal?
Hello,
I'm trying to measure the time and frequency spectrum of a vibrations signal.
My time plot seems to be ok, but my FFT graph doesn't look right.
An expected vibration FFT graph of a bearing should look like peaks at various frequencies, but my FFT graph looks only like a linear line.
Does anyone know what's wrong with my attached program?
Thank you.
Y.Yang
Attachments:
3 axis white and green sensors v2.vi 122 KB
Your code looks fine. I double checked how you're acquiring data, and it seems fine. I'm pretty sure that you are acquiring an FFT and the graph is just not scaled correctly. Do the following:
Right Click Waveform Graph 2 >> X Scale >> AutoScale X
Right Click Waveform Graph 2 >> Y Scale >> AutoScale Y
I've also attached an example of what I've done to get the FFT from a simulated signal.
Che T.
Applications Engineer
National Instruments
Attachments:
FFT.vi 67 KB
fft.png 43 KB
Similar Messages
-
How can i measure the speed of the fan in sound and vibration signal simulator box
how can i measure the speed of the fan in sound and vibration signal simulator box
provided the values tach out:2 pulses/revolution and maximum speed = 6000rpmHi. I tried your suggestion and I could not get it to work well. In
fact it worked better without the running average (which suprised me).
I also played with the number of data points but still could not get it
to work well.
Do you have any other suggestions on how I could sort this problem out?
I
have attached a screen shot of the signal. To recap, I'm trying to
measure the'y' position of the flat regions of the signal. The signal
does not have a constant level, so this 'y' position varies with time
in a non-unform manner.
I am currently differentiating
the signal and selecting the y position when the differential is equal
to zero (within a tolerance band).
In the screenshot, the
signal has been zeroed using the method I have described above.
However, it occasionally has glitches which may be caused when the code
picks up a zero gradient at a peak or valley in the signal.
I therefore need some kind of algorithm that only measures the position of the flat regions.
Many thanks
John
Attachments:
screenshot.gif 121 KB -
How to use wavelet transform in vibrational signals?
plzzz....show the explaination of wavelet transformation in vibrational signals and also help me in understanding the waveforms......................
I am not a wavelet expert, yet I would experiement with the example in the application LLB for engine knock. In general wavelets are used to extract impact events in vibration signals.
Do you have a data file of your vibration data? What are you hoping to detech?
Preston Johnson
Principal Sales Engineer
Condition Monitoring Systems
Vibration Analyst III - www.vibinst.org, www.mobiusinstitute.com
National Instruments
[email protected]
www.ni.com/mcm
www.ni.com/soundandvibration
www.ni.com/biganalogdata
512-683-5444 -
Acquiring Frequency Content of Vibration Signal
Hi.
I am trying to find the frequency content of an incoming signal from a geophone which has a 500 Hz vibrational signal on it. However, using two different methods, I find that I am only given a large DC component for the frequency spectrum of the signal. I have two different methods set up in a case statement to make it easy to try each one without having to rewrite code. The first method is to just use the FFT function (in the attached picture I have a high-pass filter on the front to try and block the DC signal, but this only blocked the DC signal and did not make the 500 Hz signal any more noticeable). The second method uses the Power Spectrum function with my array data converted to waveform for input.
The first picture shows the two different methods I tried. The 1st picture with graphs is the result I get using the FFT method. The 2nd picture with graphs is the result I get using the Power Spectrum method. Any information or advice would be greatly appreciated. I can provide further information upon request.
Thanks.
Attachments:
2methods.jpg 41 KB
method1.jpg 106 KB
method2.jpg 115 KBWell, first thing, it would be a lot easier for someone to help you if you were to attach your VI to a post than to send those little pictures. Take out anything that is irrelevant or proprietary, fine. Please set up labels and scales for your axes so they reflect your data, don't just use the default labels and arbitrary scales. Taking a wag that your bottom "time" axis is scaled to the number of data points (0-9999) and your signal is actually a 500 Hz sine, you are actually only taking about 200 points per wave, instead of 600, like your VI picturette says. Even though you would certainly be above the Nyquist frequency for sampling, it throws everything else into doubt because you haven't described it accurately.
Second, if I were to also assume that the tunnel into your case structure is the array you want to get frequency from (here's where attaching the working VI comes in), you are feeding one point at a time into the FT or PS functions. With one point at a time, it'll be real hard to get any more than a DC frequency. You need to feed the whole array in for the spectral analysis functions, or at least a larger portion of it. You've just got a single point, followed by 2999 zeros, at least for the FFT portion.
Cameron
To err is human, but to really foul it up requires a computer.
The optimist believes we are in the best of all possible worlds - the pessimist fears this is true.
Profanity is the one language all programmers know best.
An expert is someone who has made all the possible mistakes.
To learn something about LabVIEW at no extra cost, work the online LabVIEW tutorial(s):
LabVIEW Unit 1 - Getting Started
Learn to Use LabVIEW with MyDAQ -
How do I make phone vibrate longer for a text message?
I have an iphone 4s and I am wondering how I can set the vibrate longer for a text message. I have it turned on. I have set the vibrate to "Rapid".
I vibrates long for a phone call, but I want it to vibrate longer than a short burst, which is repeated later, on a text message.
Can anyone help?You can't.
-
How can you post comments during signal aquisition?
How can you post comments during signal aquisition? For example, while acquiring your signal, you want to post a comment which the temperature reads at "30 seconds" from your relative start time (t=34 sec into recording)
I have the LE package where events, alarms, etc cannot be used. Are there other ways that the user can mark an "event" during recording?Hey hkim,
If you know how long it will be before you want a message to pop up you can simply include a sequence structure and in the first sequence have a wait time of your desired length and have the message pop up and display in the second sequence frame.
Hope This Helps,
Doug B
Applications Engineer
National Instruments -
How to install sound and vibration toolkit 8.5
Hello all, I have just started using labview and would like to run the "SVXMPL_Third Octave Analysis for Multiprocesor" example as an example for multithread programming, but I run into the issue that the "Sound and Vibration" toolkit is required before running the example. I have installed the labview 8.5. I have gone through the posed link and gone through the list of products installed in my machine (ControlPanel>Add and Remove Programs> National Instruments Software), but I couldn't find the "sound and vibration toolkit". I have tried to run the installation setup in order to add the toolkit. it looks like I have already installed all the available software. I don't know how I should install the toolkit. I appreciate on any comments on how to install the toolkit. I appreciate if you can help me on how to install "sound and vibration toolkit" in my machine.
Never mind. I got it.
-
I want to connect a FLIR camera to my iPad. How can I submit a PAL signal to my iPad?
I want to connect a FLIR camera to my iPad. How can I submit a PAL signal to my iPad?
Thanks, too bad. Now I have to get a different tablet, ****.
-
Living in an apartment, here it has only wireless (no wired cable in the room) signal using for the internet connection. I've an airport express (new) ,so how can I do for extending signal (wireless) for using in myroom. because the wireless signal is so weak.
Unfortunately, you won't be able to. In order to do so, you would have to configure both the AirPort Express and the other wireless router for a WDS. Since it will unlikely that the other router is another AirPort, nor will you have the ability to administer it, you won't be able to get this accomplished.
-
How do i split the digital signal for PIP?
My tv requires 2 separate A/V inputs to use PIP. How do I split the incoming signal without affecting the signal strength to STB? Everytime I connect a slpitter, the signal looses stregth and I can't HD out of my STB only digital, not HD. Is there a fix or solution for this problem?
DcmFD wrote:
My tv requires 2 separate A/V inputs to use PIP. How do I split the incoming signal without affecting the signal strength to STB? Everytime I connect a slpitter, the signal looses stregth and I can't HD out of my STB only digital, not HD. Is there a fix or solution for this problem?
It is just the nature of beast in that when you add a 2:1 splitter, you will lose 3.5dbm of signal strength (more loss per leg the larger the splitter.. IIRC a 4:1 splitter a is 7 or 7.5 dbm loss.)
How many splitters do you currently have from the ONT to that STB? Do you have any 4:1 splitters in the path that you could swap with a 3:1 or 2:1 (leaving no open legs)?
I will leave it to someone else to recommeand a MOCA amplifier, but that may be you only possible solution. It would have to be a MoCA amplifier, as the STB requires 1150Mhz to receive guide info, etc.. A traditional signal booster typically does not pass frequencies higher that 850-950Mhz. -
After load .dbc file to the MAX, How to get activate the CAN signals?
Actually, i am new to labview and have some basic concepts. I am working on the CAN signals. I want to get activate the necessary signals alone. I know how to load the .dbc file to MAX. But after loading the .DBC file to MAX, i dont know how to activate the wanted CAN signals alone. For example, if i need to activate and control the speed CAN signal alone. i am not able to activate it.
Can anyone explain how this can be done.hi,
try to download the file from the applicarion server using the dataset operations. and store in the internal table
thanks -
How to deactivate the Touch vibration in Nokia Lum...
How to deactivate the Touch vibration or keytouch vibration in Nokia Lumia 620 ?
THIS is applicable in your case too ..
-
How to make phone phone vibrate through j2me code
how to make phone phone vibrate through j2me code
thanks in advanceSome like this
Display.getDisplay(this).vibrate(800); -
How to continously generate a voltage signal with dynamic amplitude.
Hello all,
I am looking for ideas and pointers (help in other words). I would like to generate a voltage signal (sine for example) on a AO of my NI cRIO-9263 (DAQmx). The signal should be:
continuous (without jumps ie. smooth)
dynamically able to be change the amplitude, frequency and sampling rate.
interuptable so that the AO can be turned off.
I have tried to use the DAQ Assistant but once it runs in continous mode, I have the impression that the waveform should not be changed. Is there maybe a way where I send repeatedly N samples of the waveform to the AO and gain more control over the signal that way. But if I do that how can I ensure that the signal is continous?
Further more this output has to be generated in an event application ie. in the background.
Your ideas and input is appreciated. Thanks, BernieSee if this example VI helps
Ches this one too -
Sound and vibration signal simulator box
When i am giving 0 to 5volt output from sbRIo to the sound and vibration signal simulator box to control the speed
the fan rotates very slow but when i a potentiometer present on board(manual control) there is linear relation with the input and output...
Max RPM being 6000
when i give output from the controller previously it was running on 4000 after few days 3000rpm and then 2400 now its very low and almost 1000 RPM
may i know the solution to rectify this...If is the fan controlled by output voltage and you have corrected value of voltage, there is no problem in code but problem is with fan.
Simyfren
Maybe you are looking for
-
how do I remove a picture on my desktop
-
in our developer.apple account email which given for security question is not belong to us . so we have forgot security question now . when we trying to recover is going to some diffrent email id which is not belong to us.
-
How to achive Geo Targetting in Weblogic Portal 10.3
Hi, We have a requirement of Geo Targetting in Weblogic Portal 10.3. Requirement is that once the Portal is rendered first time, based on IP tracking, content & services for that region need to be shown. Need to understand is there any API or feature
-
Shutting Down Oracle Normally in Unix
Hi All, We faced a problem since 2 days before that our HP-UX(B11.23, ia64) has been restarted due to a known bug. according to this bug the o/s shutted down itself. When it do so it kills one of the oracle RAC instances that we have. Is there a way
-
What Function will replace 0 & NULL?
In Oracle simple update statement, what function should I use to update a column with a new value following below rules: Replace current "0" or NULL with the new value If there is an existing value, do not update it DECODE would work in select statem