Auto frequency increase of simulate signal vi

Hi everyone. I am pretty new to labview. I want to increase the frequency to a simulate signal vi using array of numbers. the for loop should step through the array and output a frequency that will serve as input to the simulate signal vi every 5s changing the frequency from 10hz to 20hz, to 30hz and so forth until bout 1khz.
attached is a vi i have written but something seem not to be accurate
Solved!
Go to Solution.
Attachments:
Frequency Simulator.vi ‏63 KB

Hello marco73
The red dot is the conditional terminal.
You need to enable it for your for loop.
To enable the conditional terminal, right click on the for loop and select "Conditional Terminal"
Derick Mathew

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Timed increase in frequency into "simulate signal.vi"

Hi all, I'm an absoulte beginner with labview so any help would be greatly appreciated, I want to increase the frequency of a generated sine wave, created using the simulate signal.vi, in set increments over time.
In other words I want the simulate signal.vi to produce a sine wave that will over a set period of time increase in frequency from say 39.5kHz to 41.5kHz, in increments of 0.1hz.
Thanks in advance for any help.
Solved!
Go to Solution.

What are you unfamiliar with? All of the express functions have their name and you can use the search button on the functions palette? The only only thing you might need is a shift register and you get that by clicking on the border of the for loop. You might want to check the free tutorials.
You don't mention which version of LabVIEW you are using so here it is as 8.0.
Attachments:
sweep.vi ‏70 KB

Simulate Signals DAQMX

I am using Simulate Signals which is generating a 125hz square wave with a 10v amplitude, then sending that singal to DAQ Assistant for an analog out. Somehow the frequency seems to be changing to the DAQ Assistant analog out, therefore I am not running 125hz. I notice this when the samples per second (hz) in the Timing section of Simiulate Signals is increased or decreased. Is this just a sampling miss match?? I am sampling analog in data with another DAQ Assistant to capture data at 10,000 samples/sec(trying to capture accurate data of a very fast valve), then writing to a spreadsheet. Thanks for any help

Hi TMDATA-
What type of DAQ card are you using? How are you verifying that the output frequency is not the rate you specify?
I have tested with the attached VI and seen good results when measuring digital frequency on a counter of my MIO M Series card. You will notice that I have chosen "Use Timing from Waveform Data" in the DAQ Assistant Express VI. This ensures that the timing information requested in the Simulate Signals VI is passed to the DAQ Assistant for task timing control. I have verified that the actual output frequency closely follows the frequency requested using the Simulate Signals Express VI.
Please give this method a try and if you continue to have problems please let us know how you're verifying the output frequency.
Hopefully this helps-
Message Edited by Tom W. on 09-08-2005 04:30 PM
Tom W
National Instruments
Attachments:
AO Test Frequency.vi ‏235 KB

Simulate Signal Express VI is sending two periods of the wave per loop iteration - how can I reduce this to one period?

Hello,
I've been trying to use the Signal Generator Express VI and DAQ Assistant in order to generate an output waveform, as seen in this NI tutorial video:
http://www.ni.com/academic/students/learn-daq/generate/ (timestamp is at 2:07 for what I'm trying to do)
For background, I'm trying to move a piston device using Labview. The sine waveform is intended to move the piston at a smooth speed. For every loop iteration, the Simulate Signal VI running into my DAQ Assistant moves the piston to its maximum displacement and back twice. I cannot determine why this is occuring.
The settings in my "Configure Simulate Signal" tab are as follows:
Frequency: 1Hz
Phase: 90 deg
Amplitude: 2
Offset: -2
I would like my piston to only reach its maximum displacement and return for every iteration of the loop. I've tried adjusting all of the settings within "Configure Simluate Signal" but I can only work in even numbers - sending the piston back and fourth two, four, or eight times, ect.

The Simulate Signal VI is set for integer number of cycles and the default frequency set in the Cycles per Second control is 3.75 Hz. That results in the signal containing three complete cycles and the data array contains 8000 elements, not the nominla 10000 specified in the Express VI dialog.
If you only want one cycle, you need to specify the signal so that you only get one. Either reduce the frequency or reduce the number of samples.
As you have noticed Express VIs do one thing exceedingly well: They obscure what is going on inside. I pulled your signal generation code out into a separate VI and then created a generator which will generate the same signal but allow you to select the number of cycles. It uses the Sine Waveform.vi from the Signal Processing >> Waveform Generation palette.
I also recommend that you change the structure of your program. The use of sequence structures is discouraged in LabVIEW because they defeat dataflow are very inflexible when changes need to be made. A Producer/Consumer Design Pattern plus a state machine would probably be a good choice. This will allow separation of the daq acquisition from the saving to file so that the timing of one does not constrain the timing of the other.
Setting the Analog Input Read to read multiple samples simultaneously and using the hardware timing of the data acquisiton device will get data faster and the timing will be precisely (compared to software timing) controlled by the hardware.
Writing to the same file in parallel loops probably results in some strange behavior such as differing numbers of writes from acquired data compared to generated cycles. As the file grows, the writes may slow down due to the OS needing to fragment or reallocate space for the file.
Lynn
Attachments:
Signal generator.vi ‏49 KB

Simulate Signal phase shifting loop

I am trying to use a loop to phase shift a simulated signal across 360 deg. My loop will change amplitude, frequency, offset, but it won't change the phase, does anyone know how I can do this? I have attached a code that shows the fundamental problem.
Solved!
Go to Solution.
Attachments:
SimSigPhaseShift.vi ‏34 KB

When you wire a graph to it and set the graph to ignore timestamps, you see the phase shift. If you wire a chart to it, wire a true constant to the reset input of the simulate signal.

How to use the discrete unit delay function with the simulate signal as the input?

Hi there,
I want to use the simulate signal as the input. First, i downsample the input with the downsampler.vi. Then I want to feed the output of the downsampled signal to the discrete unit delay block and display the delayed signal on the graph.
Somehow I can't use the delay block properly, do anyone know how to fix that?T_T
thanks!!!!
Ivy
please see the attachment
Attachments:
test.vi ‏164 KB

Hi nozombie,
In your VI the Delay VI only delays the measurment for one interation of your simulation loop. What are the results that you hope to see?
Regards,
Mike Altmann
LabVIEW Platform PSE
National Instruments

Sound File not creating from simulate signal

I am trying to create a white noise sound file.
100 Hz to 8000 Hz 100ms long with a 10 ms ramp up and 10 ms ramp down.
I have been able to create the signal and sound in this vi.
Create sound - 8000 hz white noise
High pass filter - remove noise below 100 hz
ratio window - causes ramps
turn back into waveform - why oh why
normalize after filtering - for some reason the filtering changes the height of the whole waveform, if you have a solution to this......
play back sound
write sound to wav file.
The problem is, I can only get a file as short as 500 ms. I did this by changing the simulate signal options selecting 8000 samples at 16000 Hz.
If I select 1600 samples (the number of samples needed for 100 ms) some error occurs in the writing process, and the file thinks it's still open by labview. If I close labview, the file still does not work. How can I do what I need to do? Why can't I just reduce the number of samples to 1600 and get a 100 ms long waveform?
-Regards
eximo
UofL Bioengineering M.S.
Neuronetrix
"I had rather be right than be president" -Henry Clay
Attachments:
white noise generator.vi ‏169 KB
White noise generator.PNG ‏40 KB

The Labview sound system is something that NI do not care much about. They actually neglect it. Errors reported in version 8.6 are still not fixed in Version 2010. And if they fix errors you can be sure some new errors will be introduced. What you can try to do is using the old sound system (used in 7.x) for writing your data to file. In your case it should have much to say. You will find the old sound system here ..\National Instruments\LabVIEW 20xx\vi.lib\sound\sound.llb
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)

How to control the variables in 'timing' in simulate signal palette by user numeric control?

is there a way to control the timings of the simulate signal function (i.e. samples per hz, num of sample, etc) by user input (numeric ctrl)? You could easily do so for amplitude, freq, etc but not the timing.
Many thanks,

Are you referring to an Express VI?
I don't typically use the Express VI's because they do not offer the customization that I need or want. They are configured by double clicking the icon and all settings are from within. You already know that. Some Express VI's do offer more controls. But this one has only the error in control.
However, you can right click it and select "Open Fron Panel".
It will ask you if you want to convert the Express VI to a standard sub-vi. Select Convert.
You will then have a subvi that has all the input controls that you need
Message Edited by Ray.R on 03-14-2009 10:32 AM
Attachments:
SimulateSignal.PNG ‏2 KB
SimSignalOpenFP.PNG ‏7 KB
SimSignalConvert.PNG ‏4 KB

NI-5122 measure trigger frequency of TTL trigger signal

I have two signal channels and a TTL trigger signal on my NI-5122. The frequency of the tigger signal is between 5 and 30 Hz. Before I want to sample the two signal channels I need to know the actual trigger frequency to calculate and set sampling rate and number of sampling points. I use LabView 7.1
What's the best way to measure the frequency (5-30 Hz) of the TTL signal connected to the 5122 trigger input?
many thanks for your help.
Markus

Jason V,
thanks for your help. So there is no programable counter on the 5122...
My freuqency is constant and I need an accuracy of <1%.
What I did meanwhile:
I make a loop of e.g. 10 triggerevents.
I record the times when the trigger events occur.
After the loop I fit a line to the time vs. iteration number.
This gives a pretty good value for the period, hence I get the inverse frequency.
I need 10-30 trigger events to be accurate.
For 10 Hz this makes 1-3 seconds init at the start of each measurement.
I can reach a relative error as low as 1e-4. That's o.k.
I did some more tweaking to allow for missed trigger events.
The whole VI works fine to retrieve frequencies up to 100 Hz.
For higher frequencies I am limited due to the millisecond resolution of LabViews 'Tick' vi.
====
For higher frequencies I would program a counter:
Start a measurement for 1000 scans and measure the time for that.
However, this is not accurate enough for low frequencies and short recording times (10-30 trigger events).
====
I also thought about Fourier transforming the signal itself and locating the peak frequency.
Same as above: This is only accurate when I record many periods.
====
The fastest and most accurate solution would be to sample the trigger signal itself.
Then I would need only one period and could detect the trigger slopes with microsecond resolution.
However, I need both input channels for recording simultaneous signals.
Conclusion:
(1) The NI-5122 does not has a programable counter on board
(2) For my application I found a solution tht works.
MarkusMessage Edited by Nepu on 03-09-2005 02:04 AM
Message Edited by Nepu on 03-09-2005 02:07 AM

Phase shift, frequency of 2 analog signals, Diadem 9.0 or 9.1

I have to acquire 2 signals: FORCE (N) and VELOCITY (m/s) for many frequencies parameter in Diadem 9.0 (5 to 150 Hz). This frequency parameter is a analog voltage output signal which is converted in frequency by a frequency vibrator instrument. The measured signals on the vibrator (force and velocity) are considered as SINE Functions. – 1) How do I measure the output frequency of the two signals and how can I save this data ? – 2) How can I estimate the phase shift between FORCE and VELOCITY ? – 3) How can I automate the estimation of the phase shift by the 145 measurement (150-5Hz) ? – 4) Is a continue measurement of Phase Shift depending on the frequency possible ? – Best Regards from Germany and from France.
Jean-Pierre, Junior Engineer Germany

Hello KenT. I have test your DIAdem exemple. Your idea with a stop-time was not bad for measuring the phase shift beetween 2 generators by 1Hz. I have used this formula by many phase shift and it works. I had change the 2 generators frequency by 2Hz, and the formula works not anymore and that is normaly because of the reduce of the periode lenght (this problem have I show on Picture 3 of the PDF Data). On the picture 6 and 7 have I try to make another solution. My new solution works only for frequency from 1Hz to 5Hz. What about frequency like 150Hz ? I don't know if you have understood what I realy want to do, but if you have any idea to resolve my problems, please write to me. '[email protected]'
Jean-Pierre, Junior Engineer Germany
Attachments:
DIAdemTexte.pdf ‏435 KB

Frequency Analysis? How do I get frequency characteristics of a signal given in .wav format ?

I am new to Labview would really apprecite your time and help...
frequency Analysis? How do I get frequency characteristics of a signal given in .wav format ?
I have attached the signal I am trying to analyze.
Have nothing to offer in return but gratitude
Cheers !
Message Edited by Komal Khalid on 04-11-2010 10:59 PM

If you have labview 8.x or 9.x you can do this. Go to help in the toolbar. Select "Find Examples" and then search for sound. Locate the "Sound File to Sound Output.vi" This example will help in your task. Remember that Labview is shipped with a lot of useful examples. That can help you in your learning process
Good luck
Ps you can also read wav files, and find examples in Labview 7.x. But I do not know the name of the similar examples in 7.x
Edit: Please use zip files then you are not able to attach files. Do not link to sites outside. The site you linked to was very annoying. Could not download
Message Edited by Coq Rouge on 04-12-2010 02:38 PM
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)

Labview crashes when selecting simulate signal

Each time labview 8.6 crashes after I selected the simulate signal function. I get an error message about ivanlyss.dll. The message is in Dutch and it's hard for me to translate but there seems to be a problem initializing the dll file.
I asked a collegue to send me a vi containing simulate signal and the same thing happened: labview crashed.

Hi Stefan,
I can't post a vi with the simalute signal since labview always crashes as soon as I select this function. I guess you are right and the best thing I can do is reinstall labview.
Ronald

How can I get the time for a simulate signal express vi waveform?

I tried converting to an array and then indexing, but every index I try only gives me the y value. See attached VI for clarification on what I mean.
Attachments:
simulate signal.vi ‏49 KB

You will have to keep track of that yourself. You are sampling at 360kHz. This means that each sample is ~2.8us. You can easily get the time by taking that dt (2.8us) multiplied by the sample index and adding the time at which the first sample was taken.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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Acquiring Frequency Content of Vibration Signal

Hi.
I am trying to find the frequency content of an incoming signal from a geophone which has a 500 Hz vibrational signal on it. However, using two different methods, I find that I am only given a large DC component for the frequency spectrum of the signal. I have two different methods set up in a case statement to make it easy to try each one without having to rewrite code. The first method is to just use the FFT function (in the attached picture I have a high-pass filter on the front to try and block the DC signal, but this only blocked the DC signal and did not make the 500 Hz signal any more noticeable). The second method uses the Power Spectrum function with my array data converted to waveform for input.
The first picture shows the two different methods I tried. The 1st picture with graphs is the result I get using the FFT method. The 2nd picture with graphs is the result I get using the Power Spectrum method. Any information or advice would be greatly appreciated. I can provide further information upon request.
Thanks.
Attachments:
2methods.jpg ‏41 KB
method1.jpg ‏106 KB
method2.jpg ‏115 KB

Well, first thing, it would be a lot easier for someone to help you if you were to attach your VI to a post than to send those little pictures. Take out anything that is irrelevant or proprietary, fine. Please set up labels and scales for your axes so they reflect your data, don't just use the default labels and arbitrary scales. Taking a wag that your bottom "time" axis is scaled to the number of data points (0-9999) and your signal is actually a 500 Hz sine, you are actually only taking about 200 points per wave, instead of 600, like your VI picturette says. Even though you would certainly be above the Nyquist frequency for sampling, it throws everything else into doubt because you haven't described it accurately.
Second, if I were to also assume that the tunnel into your case structure is the array you want to get frequency from (here's where attaching the working VI comes in), you are feeding one point at a time into the FT or PS functions. With one point at a time, it'll be real hard to get any more than a DC frequency. You need to feed the whole array in for the spectral analysis functions, or at least a larger portion of it. You've just got a single point, followed by 2999 zeros, at least for the FFT portion.
Cameron
To err is human, but to really foul it up requires a computer.
The optimist believes we are in the best of all possible worlds - the pessimist fears this is true.
Profanity is the one language all programmers know best.
An expert is someone who has made all the possible mistakes.
To learn something about LabVIEW at no extra cost, work the online LabVIEW tutorial(s):
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Trying change duty cycle in "Simulate Signal"

Hi,
Anyone knows why I can't change the duty cycle in Simulate Signal? This option appears unavailable for me. How I can access this option? I need generate a wave triangular assymmetric.
Thanks.
Attachments:
simulate signal.JPG ‏66 KB

The dutiy cycle is only for square waves, i.e. a signal that only has two possible states (on or off). The duty cycle defines the percentage of the time the signal is on during each interval.
In any of the other signal shapes, the amplitude is variable and the concept of a "duty cycle" makes no sense..
LabVIEW Champion . Do more with less code and in less time .

Auto frequency increase of simulate signal vi

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