High frequency Labview-Simulink Interface

Hi,
I am building a Simulink and Labview model to work with each other using SIT. However, before I even begin, I would like to know whether this Labview-Simulink interface will or will not be able to run at a relatively high frequency - possibly around 80 Hz? Also, if there is any tips or hints on how to make the program run faster, such as run Simulink and Labview on different computers which are connected via LAN, etc., they are highly appreciated. And if this is of any help, I am using a P4 2.0 GHz with 256 MB of RAM computer.
Thanks and have a nice day!

Lan,
A large part of the speed will depend on the size of the model. The CPU would need to be divided between simulating the model and doing the updates, but since you are looking for a high speed it is probably a simple model. I ran a very simple model and tested to see how often I could receive values from the NI Sink in the model as well as write to a parameter of the model. In this simple setup, I recieved updates from the NI Sink at a rate faster then 1000 Hz (less then 1 ms per update on average), and writing to the parameter happened a bit slower at about every 25 ms. Since it is windows these numbers are only averages and individual iterations will vary.
If you want to provide the model with a stimulus as it is running from an external input (like a DAQ
card) then you will want to use a real-time system. This functionality is also part of SIT, where you use Real-time Workshop to build a dll and example VIs for running the model on a LabVIEW Real-Time target. Building a DLL in this way you can still use the same user interface to view the parameters and values in the model, but the inports and outports of the model will be connected to hardware. In this type of simulation the rates can be significantly faster.
Carl L
National Instruments
www.ni.com/ask

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High Frequency Noise from Headphones Out Jack

I have isolated the following issue to audio that is monitored via the headphones output on the back of my iMac:
I've been encountering a very high-pitched (and at times a cycling through high frequencies) noise when working with headphones to monitor audio. It's not the headphones and the problem is not limited to any single application. The noise is sometimes barely audible, and it comes and goes - but repeatedly and often. Sometimes the frequency of the noise is so high that I can imagine that those with poor or compromised hearing wouldn't even notice it. But the highest frequencies are still detectable - kind of like a faint ringing in the ears or a ringing television set that has its volume turned all the way down.
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OK, It is very easy to reproduce the problem, just follow this steps:
(1) Insert any headphones to iMac.
(2) Do NOT play any iTunes or any application with sound.
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This high pitch sound can be heard on external speaker plug into the headphone jacks too.
BTW, I turned OFF WIFI, Bluetooth, removed all USB devices except keyboard and mouse, adjust monitor brightness, they have no effect on the high pitch, it is still there!
I am going to call the Apple Care tomorrow. Will keep you guys posted.
Message was edited by: chienlim

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.
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Certified Professional Instructor
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"... 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

Problems with displaying high frequency sine wave

Hi all,
I don't why LabVIEW has problem with high frequency display.
Someone plzzz explane me how to see a better grapth on grapth?
check this function waveform generation.vi in examples go to search and type "waveform"
set the feq to 1k.
Thanks and regards

I think that this is related to LabVIEW, but more basically to the Shannon theorem : if you want to describe a periodic function, you need to take enough samples. First, expand the x scale to see a delta t of 0.001 s (ie a period of your 1000 Hz signal). Remeber to set the autoscale property on OFF. Then go to "sampling info" and increase the sampling frequency. See the result...
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Help Counting high frequency voltage spikes

Equipment: NI USB-6229 (250 kS/sec Analog In., 16 bit DAC, 32 bit Counters and internal clocks <= 80 Mhz)
LabView 14
Problem:
I have an experimental application where I need to count voltage spikes (integer #) caused by electrons hitting a sensor. These spikes can be as frequent as 500,000 Counts/sec. The spikes are not going to be the same voltage everytime, but they will be visible above the noise so I need to allow the user to select a Threshold Voltage that triggers a real count rather than noise spikes.
Attempts:
To count such a high frequency, I deduce that I need to use a Counter Input to read fast enough, HOWEVER, I wasn't able to find a way to set a threshold voltage for a Counter Input because I believe they expect a TTL signal anyways, which I won't have. To set the threshold, I realize that Analog Input reads can be triggered at a selected level which is great but the Analog Input Sampling Rate is only 250kS/sec which won't catch every count in my project.
I have a program that uses the Count Edges channel and it is accurate within 3% of the expected # of counts. I was just testing it with a function generator and the program doesn't count unless the signal's voltage is above 2-3 V which won't work for my application. I will post what I have. Does anybody know of a way to trigger off only at selected Voltage levels using counters, or know of a way to filter through the noise to get real spikes?
Thanks!
Solved!
Go to Solution.
Attachments:
ElectronCountsTest.vi ‏29 KB

Thanks for the reply johnsold. I didn't think to use a comparator but that is good to know that I have that option. I was and still am hoping for some kind of trick to do this programmatically. One other idea that I was playing with is offsetting two or three different Reads on the same signal to read the signal at different times. If this is a possibility, it may be able to double or triple my sample rate to 500k or 750kS / sec. Anyone else have any ideas on this solution?

High frequency power measurements

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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.
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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.
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http://www.ni.com/ask
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DAQmx Error 89137 When trying to make a high frequency measurement.

I am using a PCI-6602 Timer/Counter for multiple measurements on a serial interface...
I have the clock line connected to Gate0, the enable line to Aux0 because I need to make a two-Edge seperation measurement between the two later...
But I also want to make a "Period/Frequency Measurement (High Frequency with Two Counters)" measurement...
This requires that the signal to be measured is on Source0...
I implimented the following Code:
void meas_FP_Freq(float64 *Freq0, float64 *Freq1)
TaskHandle CLK0_Freq, CLK1_Freq;
DAQmxCreateTask ("FP_CLK0_Freq", &CLK0_Freq);
DAQmxCreateTask ("FP_CLK1_Freq", &CLK1_Freq);
DAQmxConnectTerms ("/Dev3/PFI38", "/Dev3/Ctr0Source", DAQmx_Val_DoNotInvertPolarity); // Gate0 to Source0, No Error....
DAQmxConnectTerms ("/Dev3/80MHzTimebase", "/Dev3/Ctr1Source", DAQmx_Val_DoNotInvertPolarity);
DAQmxCreateCIFreqChan (CLK0_Freq, "Dev3/ctr0", "", 6000000, 6500000, DAQmx_Val_Hz, DAQmx_Val_Rising, DAQmx_Val_HighFreq2Ctr, 0.001, 4, ""); // High freq measurement
DAQmxCreateCIFreqChan (CLK1_Freq, "Dev3/ctr1", "", 6000000, 6500000, DAQmx_Val_Hz, DAQmx_Val_Rising, DAQmx_Val_LowFreq1Ctr, 0.001, 4, "");
DAQmxReadCounterScalarF64 (CLK0_Freq, 3.0, Freq0, 0); // Run-Time Error -89137 Specified Route cannot be satisfied..etc
DAQmxReadCounterScalarF64 (CLK1_Freq, 3.0, Freq1, 0);
DAQmxDisconnectTerms ("/Dev3/80MHzTimebase", "/Dev3/Ctr0Source");
DAQmxDisconnectTerms ("/Dev3/80MHzTimebase", "/Dev3/Ctr1Source");
DAQmxClearTask (CLK0_Freq);
DAQmxClearTask (CLK1_Freq);
The "Low Frequency" method works fine, but the resolution is too low...
Every help file I've read indicates I can use different PFI inputs for measurements... What am I missing?

Hi,
The reason that you are getting the error is the PFI lines are being reserved twice. You don't need the DAQmx Connect Terms functions in your code because the DAQmx driver does this for you automatically. If you still receive an error after doing this, try to changing the low frequency counter number. I hope this helps you with your application.
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Hal L.

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).
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test CIC.vi ‏49 KB
CIC 1 sub.vi ‏21 KB
Save 1Data.vi ‏18 KB

High frequency and resolution with 6036E

I am trying to drive a triangular wave signal with about 250Hz, with the greatest resolution possible. However, due to buffer restrictions and sampling restrictions, I can't seem to be able to produce more than about 10 Hz. Is there a really good way to produce such a higher-frequency signal, with no loss to resolution?

It looks like you need a faster output card. The best that the 6036E can do is about a 10kHz update rate. Do the math and that means cranking as hard as it will go, the card will only put about 40 updates in each cycle of the output waveform.
From what you said, a 10 Hz signal is ok. So if you extrapolate out to 250Hz you need to be looking for a card with an update rate of about 250kHz--all things otherwise being equal.
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

Daq 6211 high frequency ouput

HI guys.
Ive got my hands on a USB 6211 daq device. Im trying to generate a high frequency pulse output from one of the 2 counters. The frequency is in the range of 5 to 20 kHz. Can someone tell me if thats possible with this USB 6211 device?. Ive been searching but cant seem to find the answers. Are the counters on this device just for reading HIgh Frequency inputs or can they ouput them also. Any help would be much appreciated.
Solved!
Go to Solution.

That manual has helped a lot. I should have looked at properly in the first place. Thanks .
I have one more question if anybody can help. I'm using the daq 6211 to create a pulse train to control a stepper. The stepper driver takes in a pulse which in turn will turn the stepper and the frequency of these pulses determines the speed.
My problem is that, using the counter examples in labview, I only have an option to create a continous pulse train. I would like top be able to dynamically adjust the frequency while the vi is running and Ideally i want to be able to ramp up the frequency so that the stepper can get to a high speed. If i try to adjust the controls with the example vi's there is no change in frequency unless i stop it and start again with a different frequency.
Has anyone come accross this themselves or am i missing something obvious??.

Bandpass filter amplifies only noise at high frequencies and saturates the opamp output

I have designed a fourth order bandpass filter using the opamps TL081C. It is designed to operate at a center frequency of 40 kHz with a bandwidth of 2 kHz and a gain of -12.5 . I am using an SCB-68 board for data transmission and reception, one channel each for transmitter and receiver. I have grounded the adjacent channels to both the transmitter and the receiver in order to avoid crosstalk. However, at the output, I get a signal which looks like an amplitude modulated signal and is, most probably, noise. The amplitude of this signal is always around 9V, no matter what is the amplitude of the input (even if the input is 0V, the result is the same). If I scale down the whole BPF to operate at a center frequency of around 20 kHz, everything works fine. Therefore, I think the problem lies not in the design of the BPF but the use of the board at higher frequencies. Please reply as soon as possible.

You have done something wrong. You should read the manual for both the SCB-68 and your DAQ card once more. In such cases I often use MAX, and a battery as source. Then a DAQ input is not connected (floating) you will see measurements like you are doing now. Some high level voltage often modulated with mains frequency.
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High-frequencies getting filtered

Hi all, not sure where to ask this, I hope someone can give
me some insight.
When I go to a website that allows me to stream audio and
video from my webcam - it pops up the flash dialogue box to ask my
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So, when I go thru the Flash interface, it is filtered - and
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my setup - xp home, all updated, latest flash version 9....my
soundcard is an external motu-2408-mkII with ASIO drivers and
regular drivers
So, I guess my question is....since my sound input seems to
work fine, but only going through Flash does it get filtered - HOW
do I access the Flash drivers that affect this, Is there ANY info
about how flash interfaces with my audio anywhere....
Any advice will be greatly appreciated !! Thanks all, best
regards,
trevor

You might want to try out "Flash Media Encoder" for streaming
Live input from various devices. It has nice UI for setting Mp3
bitrates and can be used to publish "audio only" stream
also.

NI Mydaq gain loss at Higher frequencies

Hi There,
I am using a MYdaq for my student project, I am using this is an audio sine wave generator and analysis tool as part of the project.
I am sampling well above nyquist of my highest frequency (20K) at 100K sample rate both on my OP DAC and IP ADC and I have a buffer size of the same size on the I/P and output.
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When I generate frequencies (via the Sinewave Vi in labview - "NI_MABase.lvlib: sine waveform.vi" and my FS and #s is both set to 10000.) i get a drop in level above approx 10K starting at about -1dB up to -3dB at 20K
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Regards

Hi,
Just to for my own sanity, have I got these values right?
- Sampling at a frequency of 100kHz. (Analogue Input and Output)
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The specifications of the NI myDAQ can be found here. These specify that the device can sample up to 200kS/s for both Analogue Input and Analogue Output, meaning that the maximum clean sinusoid we can both generate and acquire should be 20kHz, with 10S to represent the wave. Higher frequencies will require lower samples and the signals will look more chopped and aliasing will occur (20kHz*10S = 200kS/s). In order to appropriately measure the 20kHz wave, we need to choose a maximum sample frequency of 200kHz for clean waves. With this in mind 100kHz sample rate should be okay.
Is it possible for me to check the code that you have written so far? What I imagine could be happening is that we're seeing these issues due to the slowness of software. If you look at your code and the DAQ VIs are continuously having to check what values to write, rather than having these values delegated down to the hardware layer prior to running the task, this could be the source of the issue. This is because in software, there is a maximum update rate of 1kHz; this is why all of the base clocks in LabVIEW software are 1kHz clocks. If we're constantly having to poll what kind of digital output values we want to write, this will affect the consistency of the generated signals.
Kind Regards,
Alex Thomas, University of Manchester School of EEE LabVIEW Ambassador (CLAD)

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