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.
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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

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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

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
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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"
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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.
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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
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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
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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.
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Signal generator.vi ‏49 KB

Increase counter frequency performance

Hello,
I want to increase the frequency performance for my period counter. I'm using a USB-6210 board and I have the vi that is attached - period measurement.
The problem is that I want to measure the period for a 8MHz signal (I know that is a lot, I would be happy even with 4MHz). The source freq for the counter is 80Hz. If the frequency is high, the accuracy is not very critical for me.
1. I get most of the time the error: "Buffer overwritten". I've seen that I can get rid of it if I decrease the frequency, but I don't want to do that . I think that another solution would be to increase the number of points that are read. I noticed that the maximum buffer size is around 9000 points (I've read it with DAQmxRead Property Node).
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4. There is another strange behavior: if the input frequency is high the frequency and the measured period increase and decrease togheter. I think that this is caused by alias. Where can I find some more information about the board limits?
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Maybe there are some small mistakes in the VI. I made it only to get a feeling of what I'm doing. I didn't chek it with the hardware.
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Paul
Attachments:
example.vi ‏32 KB

Paul,
I have added some comments to your answer.
Regards,
Jochen
KPanda wrote:
Jochen,
thanks for this information. This was what I was looking for some while.
I still have a question related to this topic: I've read that the maximum size of FIFO is 1024 samples. What does it mean?
[JK:] The FIFO is the hardware buffer on the board. In general the PCI-bus or the USB should have enough bandwidth to transfer the data as fast as they are acquired by the device, but in fact there are sometimes some latencies that require some local memory on the board. That's what is called FIFO in this context.
This FIFO is the same with the: Available Samples Pro Channel from Read Property node?
[JK:] No. This value refers to the buffer in the PC's memory that is allocated for the acquisition operation.
I've noticed that when the value for this property is passing 9000 I get the error with Overwritten Buffer. If it is like this why do I reach more than 9000 samples pro channel? Please take a look at the attachement (test1.png - screenshoot with the values / speed_test_x - the VI that I used for this measurement).
[JK:] The buffer size is not limited to 9000 values. NI-DAQmx allocates memory automatically by default. If you like you can increase the buffer size manually.
Which is the relation between maximum numbers of sample that can be read with the Counter 1D Read NSamples? In my VI there are N=250 samples. Can I increase it in order to avoid the error? If yes, which should be the maximum limit, 1024 ?
[JK:] You can increase the number of values to read up to the size of the buffer (not of the FIFO). A reasonable value is up to 50% of the buffer size, but this is not a strict rule. Anything between 10% and 90% could make sense, depending on the timing requirements of your application.
Paul
PS: I've hope that I translated the LabView terms in the right way. I have my LabView in german (but I don't know german, so it is a nightmare for me )

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I'm more concerned about the Wait inside of a Timed Loop. That is totally unnecessary. Change the timed loop into a normal while loop.
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I am trying to create a white noise sound file.
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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)

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This is my first VI. I'm passing an array of 5 values which gets concatenated together into a string. I thought it would be neat for the 5th value of the array to always be changing so I'm using the Simulate Signal VI. I have the output from that VI working right but I'm not sure how to replace the 5th element.
Thanks for your help
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Attachments:
sim signal.jpg ‏70 KB

Hi Scott,
I think you're fairly close to getting what you want! After you insert the signal into the array, you should wire the output of the Insert Into Array function into the Array to Spreadsheet String function. Right now it looks like you are just concatenating the array generated by your autoindexed for loop and ignoring the array you inserted the sine wave into.
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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.

I have a DAQ Assistant configured to read multiple channels at the same time. When I wire a graph indicator to the output, I see all of my signals jumbled together. How do I split them up into seperate signals?

I have a DAQ Assistant configured to read 2 channels at the same
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Solved!
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Yes you are right. I tried that but I did not get the result.
I just found the way. When we launch split signal, we should expand it (split signal icon) from above and not from below. It took me a while to figure out this.
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Hi Julia,
Thanks for the response. As I stated before, I have tried all of the examples available that apply. There are only three and one of those uses two counters. The two I have tried are:
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Hi nozombie,
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Solved!
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SignalExpress does not natively support joint time frequency analysis. However, check out the Sound and Vibration toolkit which expands upon SignalExpress. It may do what you want.
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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.
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Hi Stefan,
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Timed increase in frequency into "simulate signal.vi"

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