VI for capturing data at high frequency

Hi,
I have been trying to build a VI, which would read data from a machine at around 50KHz. I am accepting one analog signal from this machine, converting into digitized values and storing ALL the digitized values into a file. I could not afford to loose even one data. I would really appreciate if anyone has an example as to record data at such a high frequency.
Thanks in advance
Dhawal

One channel running at 50kHz is simple - in fact in the world of DAQ it's not even very fast. Check out the examples for seamless data acquisition. Basically, the idea is to set up a circular buffer that the DAQ writes to and LV reads from. As long as LV extracts the data faster than the DAQ is inserting it the process can run forever.
Mike...
Certified Professional Instructor
Certified LabVIEW Architect
LabVIEW Champion
"... after all, He's not a tame lion..."
Be thinking ahead and mark your dance card for NI Week 2015 now: TS 6139 - Object Oriented First Steps

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IO fails working for low frequency, but work well for higher frequency

On our customized VU440 board, we did a IO performance test for each bank and found a strange problem, in the design,we send out 24bits Pseudo random data and loop back this data to the same bank with our testing board, on which the pins for tx and rx are only connected in short circuit, one differential clock is transfered to single-ended global clock in the design, using IBUFDS+BUFG to provide the global clock for tx module and rx module.
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Hi,
What is the IO standard that you selected for the TX and the RX. How long is the loopback cable?
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OWB Support for Change Data Capture

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Mark,
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I would advise you to study the data acquisition examples and the manual of LV.
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Capturing data instantaneously after condition is met using 2 DAQ cards

Hi all,
I am wanting to sample a pulse and a sine wave at a low frequency of 1 kHz point by point sampling and upon a condition being met - the leading edge of the pulse being greater than a certain value - I the want to take a certain number (here 270) of samples of the sine wave at 50 kHz, multiple samples. I am doing this within a case structure and using a separate DAQ card.
The problem is that when the conditon is met is does not capture the data at the higher frequency straight away. It misses part of the sine wave before commencing capturing the 'window' of the 270 samples of the sine wave at 50 kHz. I want to know if there is any way of speeding this up? I am aware that using an FPGA could help but I don't have access to one.
The other solution would to advance the condition, i.e advance the pulse train by a certain amount so that I compensate for the delay in activating the high freq capture. I would need to set up this advance of the pulse train so that, after the delay in activation, it captures the data exactly where it is required to. What would be the best way to do this? I could delay the pulse train by a certain number of samples/ or delay the sine wave, or I have read that you can use the sample timer/counter within the DAQ card to change the 'trigger of the pulse train'. How would I implement this?
Attached is my vi. I would be very appreciative if you could help.
Attachments:
2 DAQ cards Low and High Freq Sampling.vi ‏29 KB

I do not have DAQmx or any suitable DAQ devices so I have not tested this.
This is a start on cleaning and speeding things up. Note that writing to the front panel indicators at 1 kHz will not work because the screen update rate is on the order of 50-100 Hz. Also charts take a considerable amount of computation beacuse they need to (1) store data in the internal buffer, (2) erase old data if the buffer is full, and (3) (slowest) recalculate all the pixels in the display for the updated data. The cart should be moved to the parallel loop. The condition True boolean will only be true for about 5 ms out of each 100. Look at the 5 ms boolean.vi attached. It runs close to 1 ms per iteration. The boolean is true about 5% of the time but I never see it change. Remove that boolean from your VI.
With continuous sampling on the pulse channel and reading 1 sample every millisecond (assuming you get that fast) when the high speed sampling occurs it takes 5.4 ms to acquire the 270 high speed samples. So, ten times per second the loop takes >= 6.4 ms for an iteration. The next sample it reads from the pulse channel is the one which was measured (acquired) at 1 ms after the previous sample. Thus, this data point is read ~5.4 ms after it actually occurred. The next time you detect a pulse, it will be 5.4 ms late. The second one will be 10.8 ms late. Eventually you will get a buffer overflow, but your data will be useless long before the error occurs.
The Dual Sampler Simulator.vi shows a possible approach to the issue. It simulates sampling both channels at high speed. I generate both a sine wave and a square wave and sample both at 50 kHz. It simulates reading 4000 samples at a time (equivalent to reading 12.5 times per second or every 80 ms). The square samples are then processed for the transition using the boolean Implies function. I do not recall whether the Conditional terminal was available in LV2012. I did not get an error when saving for previous version so I think it will be OK. The same thing can be done with a while loop with some extra logic. This does not handle the case where the transition occurs at the boundaries of the 4000 sample segment. To handle those cases use a shift register on the outer loop to pass the needed samples to the next iteration. The 800 ms Wait makes it run slower than "real" time but allows you to see what is happening.
Lynn
Attachments:
2 DAQ cards Low and High Freq Sampling.2.vi ‏26 KB
5 ms boolean.vi ‏10 KB
Dual sampler simulator.vi ‏15 KB

High frequency

Hi everyone, im pretty new with Labview, and I need a help. I would like to simulate square wave with high frequency (40MHz).
1. Can anyone help me, how can I simulate the signal (test2.vi) in a moving (time) axis?
2. I would like to catch the datas and write it into .txt or excel. I found this example (0807-LVM_Beispiel.vi). Can I get the datas like this from my 40Mhz frequency generator?
A little help would be nice. Thanks.
Attachments:
test.jpg ‏525 KB
test2.vi ‏29 KB
0807-LVM_Beispiel.vi ‏88 KB

thanks for your help.
Ive been searching, and now I've changed my test2.vi into test CIC.vi and modified it. If you may see it, im trying to simulate the signal with frequency 40MHz and, with sampling frq. 800MHz and sample rate 1000samples or max. ~300.000samples (and save it in a txt.file). Actually, my task is, that im gonna need to make a labview program that can take as many points as possible, that might be not periodic. I mean, we gonna use NI card (in near future, not bought yet) to take some input datas, and to get all the data-samples in high frequency range. Is it possible to make such a program (capture the data) without knowing in the first place which NI card that we are going to use. But i believe, we gonna buy a digitizer, digital I/O and might also mxi controller (I've looked at the offered device list) from NI. Thanks a bunch. Is it much easier after buying the devices? (like getting the device's driver and maybe program that support it).
One other question, in my test CIC.vi, im saving my points into .txt file (only the amplitude). How is the trick to take also the x-axis points (time axis) and save it in the same .txt file.
Attachments:
test CIC.vi ‏49 KB
CIC 1 sub.vi ‏21 KB
Save 1Data.vi ‏18 KB

What are the settings for capturing video from Canon HV20

Hi All,
I want to capture video from Canon HV20 with Premiere Elements 11. What kind of settings should I use to capture the video with full information?
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2) In addition, I checked "Capture to Timeline" and "Split Scenes by cotent".
Are these settings enough?
Thanks.

HV20user
Sounds reasonable, using Add Media/HDV Camcorder, but....
Have you reviewed the Adobe write up on Premiere Elements 11 DV and HDV capture firewire into it.
http://help.adobe.com/fr_FR/premiereelements/using/WS5CDA0F91-60F1-4b79-ABF6-E9E75F498DB2. html#WS2AF26FB5-4C63-4c46-9DB3-7249558F6528
The mention of Get Media instead of Add Media makes me wonder if the video's instructor was demo'ing from Premiere Elements 10, but...
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NTSC HDV HDV 1080p30 or PAL HDV HDV 1080p25 depending on if you are targeting a NTSC or PAL area where frame rates are typically a consideration.
I had not done any DV or HDV data capture firewire into Premiere Elements. But, Premiere Elements 11's take over of the project preset setting would encourage me to encourage you to verify your project settings before the capture.
There are probably many more, but the following is online discussion of one Canon HV20 issue
http://forum.videohelp.com/threads/316970-video-capture-problems-HV20-camcorder-is-control led-but-no-video-capture
If you experience difficulty with the HDV capture fireware into Premiere Elements 11, you might consider what some others have done in this regard, that is, use HDVSplit for the capture firewire and then import the split (.m2t) clips "Add Media" into Premiere Elements 11 with the appropriate HDV HDV 1080p (1440 x 1080 HD anamorphic 16:9) project preset.
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Best way for capturing HDV

Best way for capturing HDV
using easy setup setted to HDV1080 50i (camera is a Sony HDV HC1) captured video look like sh...
and when exported with compressor is worst!
some idea?

Ok fantastic ! you are right (the frustration was talking for me)
video is shooted in 16:9 HDV 1080 50i
Captured video looks:
full of orizontal lines (that look like scan lines) expecially evident on figure edges and on motion subjects
and
like it was resized 1440x1080i from a different lower resolution
video is exported with compressor
MPEG-2 3.7Mbps 2-pass 16:9
Description: Fits up to 150 minutes of video with Dolby Digital audio at 192 Kbps or 120 minutes with AIFF audio on a DVD-5
File Extension: m2v
Video Encoder
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Width and Height: Automatic
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Field dominance: Auto detect
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2 Pass VBR enabled
Maximum data rate: 7.5 (Mbps)
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software is Final cut Studio HD
camera is Sony HDV HC1e
hope I wrote all the info
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Hey,
I'd like to know if there are developments in measuring electrical high frequency signals with labview without using an extern power analyser. At the moment i'm using a yokogawa power analyser but i'd like to know if it's possible to log HF signals without the help of a power analyser... Are there NI products on the market for this purpose?
Thx,
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Hello,
In the case of frequencies up to 200 KHz, NI can provide several solutions using the 'standard' data-acquisition boards or digitizers (scopes), from a low to very high accuracy solutions.
A good solution can be one of the high speed M-series boards (PCI-625x). These boards have up to 32 multiplexed channels with a resolutions of 16-bit at a speed of 1 MS/s (500 KHz).
A better solution would be a S-series boards. These data-acquisition boards sample all input channels simultaneously. We have boards with 2, 4 and 8 channels and sample frequencies of 10 MS/s (up to 5 MHz if needed). S-series board are the boards with product numbers PCI-61xx.
The best solution is to use a digitizer (scope). Also here a lot of possibilities going from low to higher bandwidth and resolution.
The most flexible is the PXI-5922. A 24-bit digitizer if you sample @ maximum 500 KS/s. This board only exist in the PXI platform.
Then NI has 8-bit digitizers (normal resolution for scopes) from 15 till 125 MHz bandwidth. If you need a higher resolution they have solution up to 14-bit (very high for scopes) @ 100 MHz.
Please give your local NI Office a phone call.
They have technical engineers who can discuss your needs and provide you a solution.
Best regards,
Joeri
National Instruments
Applications Engineering
http://www.ni.com/ask
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High frequency quadrature decoder (NI PCI 6221)

Hello, i would like to ask you about high frequency quadrature decoder. I am using module in DAQmx for measuring linear position. For this i am using NI PCI 6221. My problem is that i want to use this for my interferometer and we need really high speed. So I tried to use External timing whitch should be possible for this card up to 80MHz. Unfortunatelly i always will get error message that there is some kind of owerflow and my program crashes. So my question is how to get all data form this card. I know that the buffer size FIFO is only 2 so if it is impossible to get all data so i want find another solution. Is it possible let my card work alone on 80MHz and only repeatly rewrite all buffer and just sometime ask this card for sending current buffer. I dont really need all the data, but when i will ask i need to know reall position. This high speed is really necessary because my interferometer is sensitive and i dont wat to lose any steps. If there would be any possibility how to work on 80MHz and only sometime ask for sending data with position, it would be great. Sometimes i will ask not for only current position but for full buffer because i want so see what is happening during some time period, but this task will be only sometime.

Dear BMAJTZ,
The counter frequency (the maximum speed available) is configured by the Task in the background. In our case, the counter is set to detect edges, so it always uses the maximum speed available. If an edge occurs, the count value increases by 1, and this accumulated count value (stored as a binary number) is read by the DAQmx Read VI, and converted to meters. So if your encoder input is slow enough for the 80 MHz card to handle, you won't miss any ticks, even if you only read the value occasionally.
You can find further information about counters and encoders on these links:
http://www.ni.com/academic/students/learnlabview/digital.htm
http://www.ni.com/white-paper/7109/en
Also if you can tell me the approximate frequency of your encoder signal, and how often you nedd the position info, I can do some benchmarking for you to see if your card is capable of the task.
Best regards:
Andrew Valko
National Instruments
Andrew Valko
National Instruments Hungary

HQ vs standard pro res 422 for capture Help!

This is my last question (I think).
Would standard printed out on hdsr essentially look the same in this situation that I shouldn't bother with the HQ?
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Nobody calls me a gentleman and gets away with it!
There are many resources to heop you decide on a ProRes codec appropriate for your task. However, youmust weigh the processing cost of inadequate hardware against the possibly indiscernible difference in the HUGE difference in file sizes and heavy lifting.
http://16x9cinema.com/blog/2009/7/31/sorting-out-the-apple-prores-family.html
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ProRes 422
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Types of Apple ProRes Codecs
The Apple ProRes format comes in five versions: Apple ProRes 4444, Apple ProRes 422 (HQ), Apple ProRes 422, Apple ProRes 422 (LT), and Apple ProRes 422 (Proxy). The following list describes the features of each version. For a complete comparison of the relative data rates of the Apple ProRes codecs, see Apple ProRes Format Specifications.
Apple ProRes 4444
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Direct encoding of, and decoding to, RGB pixel formats
Support for any resolution, including SD, HD, 2K, 4K, and other resolutions
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Apple ProRes 422 (HQ)The Apple ProRes 422 (HQ) codec offers the utmost possible quality for 4:2:2 or 4:2:0 sources (without an alpha channel) and provides the following:
Target data rate of approximately 220 Mbps (1920 x 1080 at 60i)
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Roughly 70 percent of the data rate of Apple ProRes 422 (thus, smaller file sizes than Apple ProRes 422)
Higher quality than Apple ProRes 422 (Proxy)
bogiesan

Provide simple example for Arbitrary data sending through NI4551(DSA)

We Converted NI-DSA function palette
in LabVIEW under Application
Examples>>Advanced>>Arbitrary Output Example.
But, We not exactly getting arbitrary wave. Our arbitrary data is correct. I think there is a problem with FFT settings. So Please Provide simple example for Arbitrary data sending through NI4551(DSA)

Hello Sateesh!
First, what versions of LabVIEW and NI-DSA are you using. I have been searching around for the example you are refering too and I am not able to find it. Are you creating and arb. wave in the frequency domain and then performing an FFT to get it to the time domain? Next, remember your wave will only be as exact as the AO specs. of the hardware...
The output conversions occur simultaneously at software-programmable rates from 1.25 to 51.2 kS/s in increments of 47.684 µS/s. The analog output circuitry uses eight-times oversampling interpolators with 64-times oversampling delta-sigma modulators to generate high-quality signals. Software-programmable attenuation of 0, -20, or -40 dB is available on the output channels. The PCI-4451 has excellent amplitude flatness of ±0.2 dB within DC to 23 kHz, and a THD of -90 dB at 1 kHz.
Now, as far as obtaining other examples If you use the LabVIEW example finder and goto Hardware Input and Output>>Traditional DAQ>>Analog Output. I would also in the lower right hand corner of the Example Finder select your 4451 this will show you all examples that work with your hardware. I hope this helps a little but please give me more details we will go from there. Have a great day!
Allan S.
National Instruments

VI for capturing data at high frequency

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