Save Power Spectrum from ni5660

I am using ni5660 to capture the power pectrum using "ni5660 Power in Band" example.
Is it possible to save the power spectrum for later use? In which format can it be saved? Is there a VI that will do it for me?
When I mean the spectrun data I mean the output of "ni5660 Read Averaged Power Spectrum".
Thanks.

Hi,
Using any of the File I/O VIs within LabVIEW should work fine for this. I have attached an example of how this could be implemented by writing to a binary file. When streaming data in the way you intend to with this example, the binary file format is recommended because it is more efficient in terms of space than other file formats. In addition to the modified example I have also attached a sample VI that shows how you can read back the data written to the file and confirm that the spectrum actually was saved. Let me know if you have any questions.
Regards,
Andrew W
National Instruments
Attachments:
ni5660 Power In Band w Binary Write.vi ‏57 KB
Read Binary.vi ‏243 KB

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Save Power spectrum

Hi
I would like to save a power spectrum ( about 80000 lines of data) as a file that i can later plot. When i write the cluster (coming out of FFT Powerspewctrum.vi) to an excel (excel works only upt o 56000 or something like that, so i can´t use it anyways) or .txt file using the a combination of open -write -close file i get weird number and letters and not the data i´d like to have. Which data format ( iwould like to make graphs in origin) and vi´s should i use to export the spectrum or is it the best to extract the y-value of the spectrum (magnitude) using the unbundle by name .vi and export it as txt?
Thanks for any help

I believe this is also something i can use for my application, however, when trying to recreate the code in LabVIEW 2011 SP1, the connections between the For Loop and the Close File return an error that the data types are different.The Path wire returns that the source is 1-D array of byte stream file reference with the sink being byte stream file reference. The Error wire returns that the source is 1-D array of cluster of 3 elements with the sink being a cluster of 3 elements. How would i go about fixing this?
I plan on using this to write to the file from an accelerometer connected to a NI-9234 c-series module through a cDAQ-9178 usb chasssis. So my intention is to use this as a subVI to connect the accelerometer signal from the DAQ Assist of another VI. I am trying to record the spectral data. Attached is the attempt at recreating your code.
Attachments:
Save Power Spectrum.vi ‏55 KB

Signal-to-Noise ratio from Power Spectrum?

Hi,
I have a feeling this is a basic issue but for some reason I'm not getting it. I hope this forum can help.
I have a Power Spectrum (freq on the x-axis and power on the y-axis) and I am trying to determine the signal to noist ratio of the rf signal live.
I am using LV 8.5 and have the spectrum toolkit and am using an RFSA in a PXI chassis.
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- rf curious

Hi Rf Curious,
This questions does not have a simple
answer but let me share my thoughts and you can decide what it makes
most sense for your application. For signal to noise ratio (SNR) you
should have ideally the power of the signal and divide it by the power
of the noise. The problem here is that you are looking at both at the
same time (rf live signal). Depending of what type of signal is it, you
can recreate it and substract it from the spectrum (you will need to
recreate the phase and magnitude and delete it from the phase and
magnitude of the spectrum). This is normally done with simple signals
such as a tone.
If you don't have access to the magnitude and
phase of the data, and you only see the spectrum, then you will have to
do things different. You can probably measure the power of the signal
by measuring the power of the band where the signal is located. Then,
you can terminate your input and measure the power of the noise of the
instrument (with same attenuation and RBW settings) and have a rough
estimate. This method should have better results when S >> N. You
can also take the adjacent channel (or further) noise reference.
Finally,
if your signal has a pretty flat spectrum, then you can only take the
difference between the noise and the signal since they both have the
same RBW.
If by now, you have found other methods, feel free to post your ideas here for any other person that come across this problem.
Regards,
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National Instruments

Calculate SNR from Power spectrum (Urgent)

Hi. I have used simple blocks like PSK modulator,white noise,phase noise,tone interference, up and down converter and demodulator in a chain to simulate a noisy channel and also perform modulation in LabVIEW. I would like to know is it possible to calculate SNR from the power spectrum live for this channel? Is there any function avaiable in Modulation toolkit to calculate SNR from Power spectrum?
Thanks
Solved!
Go to Solution.

Hello en99,
The Spectral Measurements Toolkit provides VIs to calculate the 'Power in Band'. By taking the ration of this VI and the apparent noise level, I believe you should be able to calculate the SNR.
The screenshot shows where this VI can be found:
George T.
Applications Engineering Specialist
National Instruments UK and Ireland

Basic accelerometer-power spectrum readings

Hi all,
I'm new to Labview and am trying to create a simple power spectrum logger. I've had a look at multiple tutorials but am stuck getting to places (most of the tutorials require sound and vibration toolkit, are really old and incompatible with Labview 2011 etc). The program I'm trying to do is:
1) Collect signals from accelerometer (4kS/s)
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My setup is:
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- NI 9234
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So far, I've managed to get the signal readings (XYZ axis) and merge them, put them into a 'Collector' block and then output them to the power spectrum block. I've very crudely used a 'Time Delay' block to set the sample rate (which I know is probably not accurate, but I cannot figure out how else to do it). I'm having a problem figuring out how to input the sample rate into the collector, which is why my power spectrum is giving me 0 to 0.5Hz (it's likely assuming the sample rate is 1Hz). I've attached my .vi.
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Attachments:
accelero.vi ‏93 KB

I think what you want is the CompactRIO vibration data logger. It does not require the S&V measurement suite, though you will find it very useful.
Check this out!
http://zone.ni.com/devzone/cda/epd/p/id/6388
It has a waveform acquisition template for the FPGA. It has a data logging state design.
You can see a Video of it working here
http://www.ni.com/mcm/wind/
Let us know if 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

Streaming data to disk, need help reading data into Power Spectrum/Octave vi

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From an unrelated thread out there on the web:
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Memory leak with Power Spectrum function

Hi
I have a memory leak on my application. By observing with the "Desktop Execution Trace Toolkit", the Power Spectrum function (from NI_AALPro.lvlib) seems to have two "Reference leak".
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Any idea ?
Thanks...
(See attachments : Desktop Execution Trace + code)
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Same problem with LV2012 + Desktop Execution Trace Toolkit 2012
Attachments:
DesktopExecutionTraceToolkit.png ‏82 KB
MemoryLeakPowerSpectrum.zip ‏7 KB

Hi Mathilde,
Thank you for using NI Discussion Forums!
I reproduce this problem with LV2012 + Desktop Execution Trace Toolkit 2012. I will look further into this.
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Thank you.
Regards,
Audrey_P
National Instruments France
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Need Help related to Power Spectrum of two signal

Hello Sir,
I have two signals of different frequencies but i want to take the FFT power spectrum of both signals at same graph . So for that case i take the FFT power spectrum of both signal indivisualy and after this build the array. so i got the one graph and all the components in same graph. Now
The problem is that in that graph i want to extract the magnitudes at each frequency, but when i extract the information from final graph it will be the " 1D array of Cluster of 3 Elements" so its information is saprate for these two signal. but i want to tale the magnitude at each frequency , how can i got this sir . Please Help me
Agnivesh

Sir it works thanks but there is one new problem is that wahen i am going to extract the magnitude for every frequency it is also works, but my question is that if my frequency is in floating point then how can i extract magnitude for that frequency. i mean i extracted the magnitude for every frequency component starting from 0 to 1...2..3...4.............so on (Frequency ) but if my frwquency id 2.3Hz so how can i do this.i am sending you my VI also
Agnivesh
Attachments:
Analysis HP Compressor test 1.vit ‏3485 KB

Power Spectrum Density conversion to Time Series Data

Hi,
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Hate to be the bearer of bad news, but there are an infinite number of time series that will generate a given PSD. You lose all phase information upon taking the PSD. For this reason I almost always save time domain data, or at least complex FFT values.

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Attachments:
ReadXYZmine.vi ‏18 KB

Again my attachment got missed out.
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LabVIEW - Wires that catch bugs!
Attachments:
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Power Spectrum

Ok here's the deal.. I acquire data (of type numeric array) from an acuqisition unit (the specifics of it aren't important for the problem) at a known sampling rate and wish to perform a power spectrum on this data. I've used the build waveform function to build a waveform from the 1D array of data with the addition of the dt value (1/Fs) and a timestamp and fed this waveform into the power spectrum vi. The spectrum is then plotted on a waveform chart.
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Attachments:
Power Spectrum.vi ‏19 KB

Strokes,
you listen to mp3 music from time to time? Maybe, you have configured your application playing those mp3 to display something called "Bars and Waves" (at least, Microsoft calls it like this in Media Player). This display is comparable to an equalizer view.
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I have a square wave that I am getting a frequency estimate from using power and frequency estimate.vi
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Sorry for the vague first post. The software was already written for the device and I am just trying to understand a few things in order to make some changes.
I am measuring the speed of a turning rotor using the square wave signal generated from a pattern on the turning rotor. I need to know the frequency of the square wave in order to determine the speed of the rotor. The pulse pattern is used in power spectrum and estimate frequency icons (appears to be similar to an example program for spectrum analyzer). The speed of the rotor is variable until it reaches steady state which can take minutes or hours. Speeds are not too high (Freq 1-100Hz). Right now the measurement is set up to sample a given number of points at a given scan rate. This means that the data most likely does not end exactly as a pulse cycle ends but somewhere in the middle of a cycle.
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Hope that gives you a better idea what's going on here.

Optimizing Power Spectrum Performance

I'm continuously acquiring data from two channels on a PXIe-5122 at a rate of 50 MS/s (100 MS/s total). I would like to compute the power spectral density of each channel while acquiring the data. I'm currently using the FFT Power Spectrum and PSD VI. I benchmarked the performance of the FFT Power Spectrum and PSD VI on its own and was processing at a rate of about 3 MS/s per channel.
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Thanks!
geoff
Geoffrey Schmit
Fermi National Accelerator Laborary

Hello Geoff,
This is Andrew Brown, an Applications Engineer from National Instruments. The FFT Power Spectrum and PSD VI you mentioned is the recommended method of determining the PSD of data channels. Calculating the PSD given your sampling rates (100 MS/s) would definitely be much faster using the LabVIEW process. However, I was unable to find a specific benchmark.
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Save Power Spectrum from ni5660

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