Understanding Vibration Analysis

First, I am very green, have taken Core 1 and Core 2 classes (Oct 2011), and have been modifying/writing small programs within my current abilities. We used to have a seasoned veteran, but he is no longer here, although my current question isn't specifically labview related. I have 2 files of data recorded in labview monitoring the analog output of a laser vibrometer. One is of a part with a loose crimp, the other is of a tight crimp and the raw waveforms are obviously very different. I am looking for a resource to help me understand what I can get out of this data, essentially on a beginner level. How do you process it to acquire frequencies, g levels, displacement, and other things I don't know about yet. A book recommendation would be fine, or should I be asking in another forum somewhere else?
Please note that I am already aware that the data recorded from the vibrometer may be suspect due to the requirements of taking that kind of data. That's all right for the moment, we will get better at this with time. I just do not have a good understanding of how to "mine" this data yet. A lot of learning to do....
Thanks for anything you can offer,
Robert

Depending upon what failure mode(s) might exist for a "loose" crimp, there can be a number of things to look for. You might see easily-identifiable changes in the spectral content of the data (in which case you need an FFT), or it might be enough to simply track the maximum value. In any case, you will need a lot of examples to figure out what to look so you can separate the sheep from the goats.
Talk to the person who designed the widget and see if they can give any insight as to what they would expect during a failure. Also don't be surprised if (when?) you find that there are multiple features in the data that need to be balanced off one against the other.
Mike...
PS: One book recommendation for any data analysis project, Tukey's, Exploratory Data Analysis - aka. "The Red Book"
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About Vibration analysis of machine using wavelet analysis and extraction techniques

I want to perform vibration analysis using accelerometer and NI DAQ please help me in VI development and how and which parameters should i extract from the raw signal. About Vibration analysis of machine using wavelet analysis and extraction techniques.
Nitesh Parmar
+91-9780900184
[email protected]

Lynn,
Thanks for the reply.
I'm attaching some pictures of the test rig. As you can see, we have a small servo motor sitting on top of the bearing, which is a small needle/thrust bearing, used in the planetary gears of automatic transmissions. The readings are being taken by a general purpose 100mV/g accelerometer, which you can see is mounted on the bottom of a fairly thick steel plate. I understand there can be some transmissibility problems when going through too much material? We seem to be getting a reading though. The only weight on the bearing is the motor and mounting plate, 5-10lbs. I considered adding weight, and that will probably be my next move.
I'm also attaching some runs I've made. One set is of a brand new bearing, the other set is of one I stuck in a sandblaster. It is now very obviously damaged, rough and noisy when you turn it. You should be able to open these files with the .vi attached to my previous post. The first tab will be the waveform, raw data. It is not accurately calibrated to g's, but I think it should be in the ballpark. The runs are comparable to each other anyway.
I'm not currently alligning the readings with the motor revolution. Maybe this is something I should look into? I have a very capable motor/drive setup for this...
I was previously using a legacy daq device, with which I couldn't wire the error lines into the digital line write tool. You are correct that I can now remove the while loops.
Whatever else I can provide to help you assist me here, let me know.
Thanks for the feedback.
Jeremy Backer
CLAD
Attachments:
Bearing Pics.zip ‏898 KB
Brand New.zip ‏3429 KB
Sand Blasted.zip ‏3426 KB

Rule of thumb for the number of averages in an FFT for vibration analysis?

I'm doing vibration analysis on rotating machinery and would like to average the FFT to minimize variations of the data (rms averaging). How does one choose the optimum number of averages?
Also, why is it necessary to specify the number of averages (for example, in the Spectral Measurements express VI) as well as telling the VI to restart averaging. Would not the latter would be sufficient when the Spectral Measurements VI is enclosed in a loop? Thanks.

Thanks for your post.
In my experience 20 is a good number. It really depends however on a number of factors.
1) does the frequency of the rotation of the machine (speed) change? If so, averaging from an FFT would not work well. I would use the Order Spectrum in the Sound and Vibration Measurement Suite if speed changes.
2) are loads changing (and speed is constant or you are using order spectrum)? If so you will want a smaller number of averages so you do not average out the effect of fast load changes.
3) try a few numbers and note when the noise floor appears stable. This may be the best method to choose the number.
4) how often do you want a result? A smaller number of averages will produce an "averae complete" result more often.
Use the averages complete boolean to gate passing on the results (to the user interface, file, further analysis, etc.). With restart averaging on, it will restart another averaging process and toggle the boolean (gate).
Hope this helps.
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

Portable vibration analysis cRIO technology???

How can I do a portable vibration analysis with cRIO technology and LabVIEW software?. Is it possible a FFT analysis in situ with
a PDA?. I relly apreciated your help. Thanks.

Jorge,
With this setup you would have several options. The cRIO actually has a processor on it that will allow you to run LabVIEW Real-Time programs for acquisiton, process and logging. The cRIO controller also has a network link on it allowing for transfer of data over a wireless network if desired. Though a PDA could perform the FFT, the processing power required may be a little taxing on the weaker performing processors found in most PDAs.
Let me know if you need any more information.
cheers,
Brett

Need help with FFT for Vibration Analysis

Hello all,
I am acquiring data into LabVIEW from an accelerometer. The acceleration (in g's as determined within MAX) time domain graph works fine. However, I wish to do analysis using an FFT spectrum. All my attemps at wiring my time domain acceleration data into various FFT.vi's have resulted in blank graphs, including the sound and vibration module VI's. I am accquiring at 2000Hz. Obviously I am doing something wrong. Can anybody shed some light on how I can get a successful FFT working?
Kind Regards
Adam

I attached an example that works well for me - gens a signal, converts to waveform data type, does FFT
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
Attachments:
Generate Signal and SV FFT.vi ‏20 KB
gen sig and fft.JPG ‏32 KB
gen sig and fft.JPG ‏32 KB

Sound and Vibration toolkit for vibration analysis

Hi guys! I am new to Labview. I am trying to use Sound and Vibration toolkit to analyse the accelerometer signal mounted on a motor through myRio. The analysis are spectral map, order tracking, power spectrum, order spectrum etc. But nothing can be seen from the output graph. The only result I get is from vibration level.
Attached is a screen shot of my vi and actual vi file. Am I doing it correctly? I really need your help guys....
Thanks.
Attachments:
Vib.vi ‏384 KB

SK,
You have serious problems in your File.VI. Why are your writing to your file and then reading it right back? Worse, there is no guarantee that the File write will actually occur before the File Read. You have a race condition set up there between those two Spreadsheet File VI's.
If you want to maintain a history of whatever has already been written to the file, you should be building it into an array and storing in a shift register. Even if your File.vi would by chance work the way you want it to, storing data in the file system is much slower than maintaining your data in memory.
As for your while loop, it is going to run as fast as it can with respect to all the functions occurring inside of it. Is it possible you are getting 14 iterations of that while loop for each frequency step that is occurring?
Message Edited by Ravens Fan on 07-25-2009 01:35 AM

ISO Human exposure vibration analysis

Good Morning,
I am trying to use LabView 7.1 with the Sound and Vibration toolkit in processing some data in accordance with ISO 5349-1:2001. In this standard, data needs to be collected in 1/3 octave bands from 6.3Hz to 1250Hz then weighted and the RMS taken. Data collection and RMS are not a problem, the challenge I am having is with the octave analysis and creating the custom weighting. Am I just missing the obvious VI's in SVT 3.1? Is there a custom weighting example? How does one perform octave analysis below the low frequency cut-offs of the existing VI's?
Thanks,
DRK

Hi DRK,
thanks for posting again. A few things:
1) In the same user manual on pages 9-9 and 9-10 there's this info:
Performing Third-Octave Analysis Outside the Audio Range
You might need to perform third-octave analysis on signals outside of the
20 Hz–20 kHz range. For example, you might need to evaluate human
exposure to whole body vibration with potential signals of interest in
the 0.5 Hz–80 Hz range. To perform third-octave analysis outside the
20 Hz–20 kHz range, use either the SVT Fractional-octave Analysis
[ANSI] VI or the SVT Fractional-octave Analysis [IEC] VI and select a
bandwidth equal to 1/3 octave, as illustrated in Figure 9-7.
2)We don't have a weighting filter according to that standard currently but we would like to discuss the standard a little more with you, if possible. Can you give us a phone number (preferably) or an email address that we can contact you at?
Thanks!
Brian Spears

Sound & Noise Vibration Analysis

Hi
We are testing a machine " Hypoid Gear Tester" basically for Acceptance or Rejection of Gear Production. We are testing PC base Labview software for this. We are using Microphone & Accelerometer for Analysis. The Enviroment is noisy 1) How to determine and elliminate this external noise 2) We need to generate a Graph or report as the attached file. I appreciate your help Thanks
Attachments:
Picture 022.jpg ‏595 KB

The order analysis tools and the sound and vibration tools provide the fundamental signal analysis for most all machinery vibration functions. However, the application level such as hammer blow test (modal), balancing, and so forth are not complete solutions.
I recommend looking at the following solution, which is based on these tools and comes with a turn-key application solution....
www.vibdaq.com
Let us know what further questions you have.
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

Understanding Frequency Analysis

I use Adobe Audition CS6 to generate abstract tones (normally between 400 Hz and 2000 Hz with 1 or 5 harmonics). For tones with 5 harmonics, when I create them there are 5 obvious power bands in the spectral frequency window, and when I do a frequency analysis (Alt-Z) there are 5 obvious spikes and nothing else. However, when I open the same sounds later on, and perform the same frequency analysis there are many other spikes present (though at lower powers than the 5 I specifically created). Why are these harmonics showing up in saved sounds? I do equate the sounds for Total RMS, does that have anything to do with it?

If you store 5 tones (let's say 10 seconds) with the tones at a reasonable level - let's say -10dB - and save the file at 16-bit depth, and select the whole file to analyse, you'll see pretty much what you'd expect/
But, what you see depends to a large extent on the FFT size you are using in the analyser, and sometimes with tone generation having the very start of the file included can do strange things to the results. If you select a reasonable section of your 10 sec file with an FFT of 8 or 16k, you'll end up with a noise floor sitting at about -120dB across the spectrum and your tones pretty clearly defined. The smaller the selection you make, the more the noise floor gets bumpy (when you hit the analyse button, the noise in the selection gets averaged out, and the more there is to average, the more it comes out to a fixed value). If you measured the SNR using the meter, you'd have a noise floor around -96dB, which is the value of all of the 1/Hz noise @ -120 dB added together across the bandwidth, and this works out to 6.02dB/bit. So the same sound saved as an 8-bit file will have twice as much background noise.
Also, you have to bear in mind that there's a difference between stopping the cursor at any point and looking at the results, and analysing a selection. Even analysing a short selection will give you a much more accurate representation of what's actually there.

Repeatable Reading variation in Noise & Vibration Analysies

We are testing the Quality of the gears based on the noise and vibration produced when the bevel and the pinion gears mesh each other. We Using SV DAQ NI PCI-447 and connected accelerometer and microphone for 1st and 4th channel respectively. We are following signal harmonics method for the testing purpose. First, we acquire the data signals of both noise and vibration and process them by the same above method and judge wheatear the gear has some defects or not. (Based on the threshold values) The problem is, each time when we run the machine, the noise and vibration signals which we acquire will be different due to this final results (Harmonic values) are also changing. We need some filters or any other solution so that we acquire noise and vibration only for gear mesh. I uploaded a picture showing how we doing the test process for sound.
Attachments:
harmonic.png ‏35 KB

If you are only concerned about peaks within a certain frequency range, you should adjust the Search Range in the settings of the Peak Search Express VI (on the Configuration tab). That will tell the express VI to only return the peaks in the frequency range that you choose.
To clean up your results, you may want to try some FFT averaging. This might help if your peaks are jumping around a little bit due to a low peak threshold that might be picking up some noise.
If you really would like to do some filtering, you could use a highpass filter to get rid of any low order (1x/2x/3x, etc) vibration that you might not care about. From your picture, it looks like you have the Sound & Vibration Measurment Suite and you are comfortable using express VIs. So, you could use the filter express VI from the palette here: Sound and Vibration>>S&V Express Measurements>>Processing>>Filter.

Sound and vibration toolkit using Keithley Card

Hello everyone,
Might be doing a project soon using the LABVIEW Sound and Vibration Toolkit(1/n octave vibration analysis required) with LABVIEW 6.1(Sorry, try convince my Boss to upgrade). We have a Keithley KPCI-3101 card avaliable to us for the analog input.
Do any of you forsee a problem using a non-NI card with the sound and vibration toolkit? I can find very little on the internet discussing using non-NI cards with the toolkit.
This might sound like a stupid question but I need to be
100% sure that there are no problems.
Thank you for any help you can offer :-)
Cheers
Jurgen

Hello Jurgen,
Of course the integration with National Instruments boards (PCI-4472 or 445x boards) is best suited with the Sound and Vibration Toolkit. However it is possible to use the toolkit without National Instruments hardware. Most of the examples that ship with the toolkit use NI-DAQ data acquisition calls. You need to remove them from the examples and substitute them for the driver vi's that your board uses. There are also a couple of examples that use simulated signals (so there is no hardware at all involved).
One thing to be aware of is the sample rate. Recommended sample rates, that are used in most examples are 51.2 kS/s. You may need to check if your board is capable of doing this.
Also all the functions use the waveform datatype, (which include
s timing information), so you need to convert your array of data to this datatype, using the build waveform function.
Hope this answers your question.
Best regards,
Erik vH.
Applications Engineering
National Instruments

Sound and vibration Toolkit 7.1 on Labview 8.0

Hello!
I kind of expect the answer is to cash out for a toolbox upgrade, but nevertheless I will ask the very logical question:
When I have an old Sound and Vibration Toolbox, how can I use it on a newer LabView Installation?
I could install, but when opening some of the example VI(SVXMPL_Averaged Frequency Response (DAQmx).vi), they do not work. The sub-VI's (e.g. svx_ClearAO_ClearAI (DAQmx).vi) have broken connections and even a mass compile didn't help. After the mass compile I have a long log of errors. So has anyone been successful in doing this without buying the newer version of the toolbox?

Hi
Let me double check the version of Sound and Vibration toolkit you installed
as the latest Sound and Vibration toolkit is version 6.0.
This information is in Measurement & Automation Explorer(MAX)
if you go to MySystem >> Software >> LabVIEW >> Sound and Vibration Analysis VIs.
As well as this, please let us know the version of your DAQmx driver.
It sounds many DAQmx VIs are broken and your DAQmx might not be a compatible version of the toolkit.
Regards,
Ayumi

GMLAN,J1939,J1587,J1508 Canbus Comms- Dynamometer, Sound and Vibration,Halt & Hass, Labview Consultant Available June '07

Will be available for 6-9 month contract June 07.
13 years Labview experience, GUI, SCADA, Canbus, Heavy Truck-Bus ECU verification, Dynamometer, Sound & Vibration Analysis. Environmental chamber shock testing experience, HALT-HASS, Durability and Life cycle, Executable VI development.

SAP SD profitable analysis

Dear Gurus,
In VF02 while release billing document time, i click "accounting overview" tap page some fields like
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                Controlling Document
                Profitab. Analysis     "
Coming. Now my problem is.
If i gone trough "profitable Analysis" tap page. "No analysis."
Their showing only codes, not price.
where profitable analysis configuration.
Thanks in advance
Satya

Hi Ramu,
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Dasaradha

Need help with vibration integration and changing units

I am far from an expert in vibration, none the less I found the following table and am now trying to reverse engineer my data that I took with an accelerometer to something I can compare with on the table.
Screen 54 of the following said to go from G's to inches/sec2, multiply by 386.1 so I wrote up a piece of code to do that along with the labview sound and vibe toolkit. We know our machine has excessive vibration but this seems to be a little redicioulous. Am I doing this correctly, please see the attached code.
Essentially how do I go from Acceleration taken with a 10.82mV/g accelerometer to inches/second and mil peak to peak. I have tried using the integration functions but I am seeing numbers that just seem too big to be real.
Is there any example code on how to do this somewhere?
Thanks,
Adam

Thanks for the reply,
I have seen those examples but I am not sure they are helping me out too much, at issue is it seems like a lot of vibration data in the USA is based off of ips (inches per second) or displacement in mils peak to peak for example see the following image. I have done quite a bit of searching but am not necessiarly finding a good article that would describe how to code up something in LabVIEW to post process my recorded data taken in acceleration units of g's and convert it over to inches peak to peak as well as ips. I see that sound and vibe toolkit has the integration function but I am not sure I am properly using it. Do you know if there are any examples of how best to get displays in such units or writeups as to how to go about converting this to something along the lines of what suppliers and other vendors are displaying vibration data to us in? I haven't had as much time recently to work on this as desired but I also have to think I am not the first one to stumble on the need to do this considering how much vibration analysis in the USA uses such units.
Thanks,
Adam

Understanding Vibration Analysis

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