Appending Square Waves

Hello I am trying to create a VI that will generate a waveform from two 1D arrays, one for the amplitude of a section of the waveform and another for the duration of that section. For example if I were to put in [1,2,3] into the amplitude array and [2,5,10] into the duration array I would receive a graph that had an amplitude of 1 for 2 seconds, then amplitude 2 for 5 seconds, then aplitude 3 for 10 seconds. I am using the Append Waveform function to do this.
I have a VI that will generate the amplitudes correctly, but the delays do not work, each amplitude is only true for one second a piece, no matter what i put into the delay array. Does anyone have any suggestions on how to force the amplitudes to be active for a given amount of time?
I have attached a picture of my code so far.
Thank you
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Waveform.PNG ‏19 KB

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Attachments:
Step Waveform.vi ‏13 KB
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Calculate Square wave Duty Cycle

Hello everyone,
I'm acquiring (with USB-6212) a square wave, "100Hz" with variable duty cycle - which can be 20%, 50% or 80% - for matters of decodification; the acquisition frequency is set to 4k. Actually, I said the frequency is 100Hz, because I get a rising edge every 10ms, but the length of the high level is defined by the communication protocol and that is what I called duty cycle (even though this does not match the exact definition of this property)
Since I need to decode the information contained by the wave, it's necessary for me to be able to tell what the duty cycle is. I've acomplished this so far by taking the derivative of the signal, then calculating peaks and valleys index in the waveform and finally subtracting them, as shown below.
It works ok almost the whole opeartion, however, the acquisition is not 100% exact. Sometimes I get the signal in the picture A, that is ideal for what I intended.
Other times, the signal is like B and the derivative amplitude does not cross my threshold, even though there is a rising edge there. I could lower my threshold to 2, for instance, but then I'd get vulnerable to the signal in picture C, which would accuse 2 peaks, instead of just one.
Anyone have an idea on how to work around this or any other method more reliable than taking the derivative of the signal?
Solved!
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Well, we can only answer question based on the information supplied! The LabVIEW Mind Reading Toolkit is still in development.
Your application is one where parallel loops may be valuable. In the acquisition loop you read data from the data acquistion device at a rate which optimizes the DAQ perfomance (the >= 2k points you mentioned). The data is transferred to an analysis loop via a queue. In the anaylsis loop you can put the data into a shift register. When more data is available from the Acquisition loop, dequeue it and append it to the data in the shift register. The Duty Cycle section will find two consecutive rising edges and the falling edge between them ( the 10 ms segment). It calculates the duty cycle for that segment. Then it uses the second of the rising edges as the first rising edge for the next segment. Repeat until duty cycles have been determined for all segments.
There are a lot of details which can be imprortant in a process like this. Many of them are dependent on other things you have not specified. What will be done with the duty cycle values? Is the raw data to be displayed? Saved to file? Discarded after the duty cycle is measured? How long will the process continue? How much data can accumulate?
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How can I output a square wave to control a stepper motor using 7332 controller?

I have the following system configuration for testing a linear actuator (LA):
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How to generate a high freq square wave on NI-USB 62xx

Hi,
I am trying to generate a 50khz square wave with an AO channel on the NI-USB 6212 (rated at 250ks/s AO). I started with the Voltage - Continuous Output.vi example but when i go up toward 50khz square wave (100khz sample rate) the edges of the square wave become rounded. The slew rate for the card is 5V/us and my amplitude is just .5V so i feel like I'm doing something wrong with the task setup.
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Hello Matt,
Right now, I think that shape of the signal that is being output is being controlled by the load on the AO.
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Can you please upload a picture of your waveform?
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How do you find the frequency of a small sample size and a square wave.

I am collecting data from ten 12v pulses that are seperated pretty uniformly. The pulses make a square wave. I need to know how to input this small sample size and find it frequency. I need this frequency to be output in a readable file. Im not very knowledgeable in labview so if you try and help me please be very descriptive.
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What have you tried so far? What parts are giving you trouble? Please be as specific as possible. Post the code you have written.
You ask about frequency measurement and then you are talking about triggering.
If you always have 10 pulses, just measure the time from the beginning of the first pulse to the beginning of the last pulse. The frequency is 10/time.
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Sorry about duplicate post. My internet connection is very slow today.
Message Edited by johnsold on 05-31-2010 12:05 PM

How to generate multiple digital outputs (square waves delayed) at 50 kHz?

I would like to generate 3 digital outputs like the picture attached at 50 kHz. Using the "digital pattern generator (marching values).vi", I can generate 3 digital square wave but without the delay time. How can I do that?
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Thank you
Attachments:
digital outputs delayed.png ‏8 KB

Hi,
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DAQmx Write Digital Channel- External Clock: https://decibel.ni.com/content/docs/DOC-11142
Regards,
Thomas

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Which data type does your square wave signal has? If it is a waveform you can get the value as an array of double with the Get Waveform Components primitve.
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Don't forget to give Kudos to good answers and/or questions

Can I generate sine and square waves with NI PCI-MIO-16XE-50 card??

Can I generate sine and square waves with NI PCI-MIO-16XE-50 card??
How Do I generate those signals?

Hello;
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Hi, is there a way to create a square wave that has an incremental HIGH pulse width and a fixed LOW pulse width?
Sorry I'm quite new with labview, any help is appreciated, thanks!
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Hi GBPC,
My name is Jack and I work at National Instruments UK.
I understand you are trying to output a square wave signal with a fixed low time and variable high time in labVIEW.
The reply above works great if you want to use the signal internally. Alternatively if you are trying to output the signal with a piece of internal or external Data Acquisition (DAQ) hardware you will want to use LabVIEWs DAQmx Tool palette.
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I need a quickly help that as below :
I am trying use PCI-6220 to acquired six signals from one rotation encoder (channel A, channel B,channel Z ,and their non-signals) .The encoder out signals will be square wave and 4000pulses per revolution. I set it rotation at 300rpm speed. I need show every square wave of six out channels in waveform and measure the A-B phase difference to check if the value is correct (designed value should be 90deg) .
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I am also having this issue and have not been able to find a solution in the forums. I am somewhat of a rookie so pardon me if I seem ignorant in any way. I am working on a graduate project where I need to produce some sine waves and I am getting more of a square wave when I output it and measure on the scope. The program I am running is quite simple at the moment to attempt to discover any errors by process of elimination. I have the sine wave generator in a while loop outputting to an AO port. I am using the cRIO 9022 with the 9269 AO module. I will attach screen shots of my code and my oscope image
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How to alternate data storage into 2 arrays with an analog square wave input? (seems that the retriggerable function is not supported by my PXI card)

Hi!
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Hello Shari,
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Dear HaI L,
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Convert square wave to saw tooth wave

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Solved!
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Use the wave generator funtions found in palette Signal Processing - Waveform Generation. There are sine and triangle waveform generating functions there. You can set the number of samples and sample rate such that it would generate a partial waveform. Then you use Get Waveform Components to get the Y values, concat the values, then use Build Waveform to build it back to a waveform. You will get a back to back output. In the following example, I used a sine and square wave because a sine and triangle were too close in appearance and you could not readily see the effect.
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Appending Square Waves

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