Spectral analysis of PDM

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  Hello Scott,

  The result of your calculation is correct, you get a frequency of 60 Hz about resolution, but how you calculated it is false. If you sample with 500kS/s you can have a maximum of 250 kHz and FFT frequency you'll 8192 lines in your spectrum, so theoretical, you would have a resolution of about 30 Hz. But the FFT on the FPGA is both sides, that is, it returns the positiv and negativ frequencies. You cannot use the negaive ones, so you have only 4096 lines left from where you get a frequency of 60 Hz resolution about.

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  Mike...

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  Yes. Without information from dt, spectral analysis function will assume a sample rate of 1.

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  I tried a few things, for example by placing the table split and merge functions or graphic waveform, outside the timed section, but this has very little effect - the main delay persists with screw FFT. These screws are already implemented reentrant, but somehow always do not perform well at the same time. Why?

  Can someone show a better performance gain in a similar VI? I'm using Labview 7.1, using pictures instead of a VI for the answers would be greatly appreciated!

  Thank you!

  

  

  Hello

  Thanks for your reply. In fact, I found the solution. Rather already internal multi-threading, the Express VI has done exactly the opposite, he broke internal capacity of multithreading, including several side bolts that were not reentrant. This means that the Global Spectral VI analysis Express is not reentrant and accelerate properly on a multi-core CPU.

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  As a courtesy, I enclose my new, 5 x faster multi-core FFT VI.

  It evolves on an Intel Core 2 Quad CPU as follows:

  LabVIEW Spectral Analysis VI Express (single or multiple instances): 1 x speed

  Multi-Core FFT VI (single instance): 2.3 x 2.4 x Faster

  Multi-Core FFT VI (double instance): 3.7 x 4.0 x Faster

  Multi-Core FFT VI (quad instance): 4.8 x 6.1 x Faster

  Multi-Core FFT VI (instance octo): x 4.8 to 6.1 x Faster (could probably use a 8-core see benefits)

  Here are the internal features of the VI of FFT multi-core Lite:

  

• detect the appearance of some FFT frequencies

  Hello

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  I use an IIR bandpass filter on this signal.

  I then use the Express-> VI of spectral analysis to trace a FFT.

  I am interested in the apperarence of a certain frequency detection in the FFT and call a function from its appearance.

  I guess I'll do that if this frequency exceeds a certain threshold of amplitude to the FFT.

  What is the best way to do this?

  cosmund

  Hello cosmund,

  The output of the greatness of the Express VI spectral analysis is a data type of cluster that includes the starting frequency (f0), the difference in frequency between two successive frequency (df) and an array that contains all the points of the scale to the FFT (size). To monitor a certain frequency of an input signal, you will need to retrieve these values.

  To do this, you can use the Unbundle by VI name found in the Cluster, class, variant & subpalette in the range of programming. When you the wiring in a data type of cluster, you will be able to each of these three pieces of information by expanding the function and selecting the items to the appropriate cluster. F0 and df values, you will be able to determine what the size array index contains the frequency you want to monitor. Now you can use the table to the table palette Index function to read the size of the FFT frequency you want to monitor.

  To call a function based on the size of the FFT, I advise to use a case structure.

  I hope this helps!

  -Abram

• AIR-AP1852E no flexconnect

  I have configured 10 AIR-AP1852E on a WLC2504 with Version 8.1.131.0 of the software, but I can't configure these ap Flexconnect mode.

  Cisco documentation by the available modes are 'Centralized Local', 'Stand-alone', 'Sniffer', 'Cisco FlexConnect', 'Monitor', 'OfficeExtent' and 'Mesh' but in the configuration, I have only "the" local mode and the "Sniffer."

  Anyone know why?

  For the release notes for Cisco, there is an article on what is not supported for the 1830s and 1850s, and Flex is not supported.  Here is the link and the link is an excerpt from what is not supported.

  http://www.Cisco.com/c/en/us/TD/docs/wireless/controller/release/notes/c...

  Features not supported on access points-Cisco Aironet 1830 and 1850
  Cisco's virtual wireless controller
  Mesh mode
  Flex mode
  Monitor mode
  Sniffer mode
  Workgroup (JWG) Bridge mode
  OfficeExtend mode
  Improved Local (ELM) mode
  WHEAT integrated
  Basic spectral analysis
  Support for Bluetooth Low Energy (WHEAT) devices on USB
  Cisco CleanAir
  ClientLink wireless Cisco 3.0
  Discovery of rogue location Protocol (RLDP)
  Compatible eXtensions (CCX) Cisco specification
  802.1 "supplicant" x for the AP on the wired port authentication
  Static WEP key for TKIP and CKIP
  Dynamic pass control of feeding (DTPC)
  Federal Information Processing Standard (FIPS) and common criteria
  Detection of Rogue 40 MHz
  Native IPv6
  Telnet

  -Scott

  Please evaluate the useful messages *.

• FFT 1 d 2D spectral data with GPU Analysis Toolkit

  Hello world

  I'm trying to implement a parallel my data 2D fourier transformation using the GPU analysis tool. Given that I've never used this tool, I tried first to implement a simple transformed of Fourier of a simple real signal to an output complex vector. For this, I found an example on the internet and adapted a bit. Unfortunately, I don't get any output, but I don't have an idea why. I have attached the VI then perhaps someone could take a look? I would appreciate if some could help me with this problem.

  Thanks to anyone who can help me

  Simon

  A brief information. I was able to understand the problem. The problem was caused by a Version of the box again CUDA Toolkit. I installed the 4.1 Version and now everything works fine.

  Simon

• Fetch forever PDM

  Hello everyone,

  I need assistance with example programs OR: niScope fetch Forever, write TDMS & read PDM.

  When I try to pick up permanently and save the data in the file of PDM, his job very well, but when I try to read the data at Labview (or convert .txt or .csv),

  I have a memory problem when I have too big TDMS data to read at a time.

  Y at - it a trick to split them first and then read them?

  The problem is read TDMS.vi don't automatically know what is the size of the file the data in the .tdms which is read.

  I think I need to use FOR the loop and offset and count under control in TDMS read block, then convert into csv. or .txt using the index number for the files created.

  Example of what I'm trying to achieve; I have 20, 5 million data in a table in the example.tdms, then I would have 6 files with the data of 3 million and 1 file with 2.5 million data, which means I need to divide.

  The other problem is, I'm trying to get the points fetched2 total to be O when I start the program and increase when I hold the backup button. In this program, I'm not there o when I keep my button 'SAVE' TRUE all the time.

  Please, any help would be really appreciated.

  Kind regards

  Yan.

  

  OMG nevermind,

  I just forgot to put the same name I used in writing TDMS.vi (Groupname & Channelname) in my TDMS.vi reading.

  So, I think that the solution is to this code example (https://decibel.ni.com/content/docs/DOC-8985) combined with a little bit more careful analysis.

  Thank you very much

  Kind regards

  Yan.

• Preserve the original dt during playback PDM

  Hi all

  I have the following situation. We have two VI; the first reads a PDM GB 3 file and allows us to extract the selected channels, which we can then decimate, reducing the size of bit, maybe a few other conversions, etc. We then record these channels in a separate file of PDM (naturally, smaller size).

  The second is an analysis VI, which allows us to have fun with the waveforms on the inside the smallest file PDM. However, when you use the function Read PDM, it seems that it converts information from dt to a default value of 1. A plausible solution is to define a data type control that allows me to choose the dt manually, before the reading of the actual process. However, this may be a bit heavy when dealing a PDM file with lots of channels (I have to define the dt for each channel, rather a PITA if I have to do this for 20 + channels).

  Is it possible to read the PDM file and extract the waveforms while maintaining the original data of the dt?

  Thank you.

  Dear Daniel,

  TDMS reading should return the dt appropriate until it has been saved successfully. Try to create a test on a small scale with writing and reading a file of small measures.

  Kind regards:

  Andrew Valko

  NOR Hungary