Biphasic square wave with interpulsation intervals

So I'm trying to get my graph to look like the copy and pasted image however I already have knobs and buttons to control duty cycle, amplitude, and frequncy. Basically I just have created the square wave, I just need a way to insert an interval and display it on a waveform graph since there is no option when simulating the signal. Thanks!

It would be helpful to see your code. But if I were doing it I would define the waveform as a repeating series of three time intervals: a high time, a low time and an off time.
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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;
You certainly can do that. The way to go about that is to use one of the Analog Output channels your board have available.
If you are using Labview to program the board, you can find good examples at Search Examples->I/O Interfaces->Data Acquisition->Analog Output->Multiple Point (buffered) Analog Output.
If you are using other Software language to program the board, you can fing examples at C:\Program Files\National Instruments\NI-DAQ\example\VisualC\AO.
Hope this helps.
Filipe

Generating square wave with variable duty cycle

We like to generate a square wave with variable duty cycle using LabView 6.1 and SCB-68 and this duty cycle comes from some PID controller programmed by LabView by reading a voltage and feeding back this square wave

the story begins with some one called separately excited DC motor
this thing sometimes changes its speed
so we are trying to keep a constant speed
irrespective of the load no matter how it changes
this comes by reading the voltage out from
the tackometer which represents the speed as voltage
then comparing this with a reference set by the labview program
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Minimum sample rate for 10KHz square wave with MIO

Need to display a 10KHz square wave input to a 16E MIO. Presently sampling 1 channel at 400KS/s. Gives me 2.5uS/sample. Even at 800KS/s-same thing. How come I can't get a decent picture of the waveform. Presently I see a ramp up-down akin to an RC time constant. At 1KHz I get a decent waveform. I'm wondering if I have something set wrong in my program. Did I miss something in determining the proper sample rate?

Hi Steve,
Are you sure you are sampling at 400 and 800 KS/s?
I thought those boards only go up to about 100KS/s.
(show your point on your plot. Are you getting 40 samples per period?)
If you really are sampling that fast, then you have partially answered your own question. There is a small capacitance at teh input to the board. A high impeadance source will combine the input capacitance of the board to give you the charge ramp you mentioned. Only solution to this situation is ussing a low impeadance output buffer between your signal source and the AI.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
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How to output square wave with pci 6110 from digital output

and the frequency of the wave should be variable and quite precise.

"from digital output" is not possible if
your timing req's are less than a second
and
you are not running Real-Time.
It can be done from the analog output port.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Creating Digital Square Wave with DAQ

Hi,
I am a new LabView user and need some help in creating digital squarewaves using simulated DAQ, and output physical channel.
Since I am only able to create a sine analog waveform using DAQ, I really need your kind help regarding this topic.
Thank you very much.

First: How strickt is your timing?
Will software timing (delay of maybe up to 20ms) be good enough?
Or do you need hardware clock based timing using the hardware timer of your 6251?
I add a event structure based version, timing will lag the executiontime of the write to output
Greetings from Germany
Henrik
LV since v3.1
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Attachments:
onofftimer2.vi ‏16 KB

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.
I also tried setting continuous samples using the onboard clock for a source and then writing an array [1,-1] but that fails at anything higher than ~8khz.
What's the most efficienct/correct way to set up a task like this? Any help appreciated. Thanks.
Matt

Hello Matt,
Right now, I think that shape of the signal that is being output is being controlled by the load on the AO.
If there is a very large impedance load attached between AO and ground, the RC time constant of the circuit is going to be very high. This will result in a large amount of time required to charge and dissipate the voltage. By increasing the frequency, the amount of time allotted for this is being reduced. Potentially resulting in the waveform you are seeing.
Can you please upload a picture of your waveform?
Can you please try to reduce the load on the AO? This can be done by disconnecting the current load and attaching a small resistor (50 Ohms should be good). Does this result in the correct waveform?
Regards,
Thomas C.
Applications Engineer
National Instruments

Why do i get ringing when i am generating Square Wave using PCI 4461 DSA Card

Hi,
when i generate square wave form DSA card PCI 4461 i am getting ringing effect as per my observation of waveform generated in CRO.Can anybody tell me why is this effect seen and how can it be rectified and removed from the signal in LabVIEW.
Regards,
Sneha

The analog outputs on the 4461 (and the analog inputs, for that matter) are band-limited by digital lowpass filters. These low-pass filters have a brick-wall response in the frequency domain, which results in Gibbs-phenomenon ringing in the time domain. See this discussion, among others:
http://en.wikipedia.org/wiki/Gibbs_phenomenon
The ringing will be excited whenever there is significant signal power near the abrupt band edge, because the abrupt cutoff will result in signal power being located just below an absence of power in the spectrum. Whenever signal power appears in spectral isolation like that, you can expect ringing in the time domain response. Your square wave consists of a series of harmonics at frequencies below, near, and well beyond the digital filter's cutoff. When the digital filter cuts off the higher harmonics, the ringing is created.
To prevent the ringing, you must create a waveform mathematically that is bandlimited already. The result will be a square wave with slower rise and fall times, but no ringing.
Hope this helps,
Ed

FFT on triangular and square waves.

Hi,
I have been computing FFTs on a some sinusoidal waves and have been doing fine, gett the right Y axis values in the units Vrms^2. For example a 10V amplitude (20v peak to peak) wave at 100 htz would give a peak at 100 htz and 49Vrms^2 since the RMS value fo 10 is 7 and 7^2 is 49. Now when I input a Square wave with the same characteristics I no longer get the same scaling instead getting a peak at a higher y value. With a triangular wave I get peaks at lower values. Can anyone explain to me why this is happening?
Thanks.
Intern NSWCCD Carderock.

Actually RMS (Root Mean Square) value of periodic signal f(t) is defined as a square root of squared signal averaged over the period T, mathematically:
f_rms = sqrt ( aver (f^2) ),
where aver (f^2) = [integral of f^2 over the period T] / T
It is easy to show that for pure sine wave f(t) = A*sin(2*pi*t / T), f_rms = A / sqrt(2) ~ 0.707*A – this is well-known result anyone can find in almost every textbook. It is not difficult to calculate exact value of f_rms for square and triangular waves. Results are as follows:
f_rms (square) = A, where square wave f(t) = A, if 0<t<c*T and f(t) = -A, if c*T<t<T (here 0<c<1 and c=0.5 for 50% duty cycle wave)
and
f_rms (triangle) = A / srqt(3) ~ 0.577*A, where I assumed triangle wave that raises from 0 to +A over 0 < t <T/4, goes down to –A over T/4 < t < 3T/4 and returns to ZERO in the last quarter of the period T
Parseval’s theorem (http://en.wikipedia.org/wiki/Parseval's_theorem) of Fourier analysis states that energy of periodic signal (=integral of f^2 over the period T) must equal to energy of its Fourier transform ( sum of squared amplitude of all harmonics for periodic signal). That’s why Fourier analysis in Labview is capable of producing signal’s RMS value in addition to its spectrum.
Now, main harmonic of square and triangular waves carries majority of signal energy, but not all of it because of presence of other harmonics. That means that amplitude of main harmonic as reported by Labview will be close to but slightly less than signal’s RMS value. This explains the results you reported in your very first post.

TWO independent square wave generators on sbrio9632 fpga

I am using sbrio9632, I need to generate 2 different PWM signals for driving 2 different motors in the same time. I`ve put 2 square wave generators but when I change the parameters (frequency, duty cycle) of the first generator, the parameters of the second generator are automatically changed. So i supose that there is only one square wave generator that can be used. Any solution ? Is it possible to use 2 different square generators on the same board ?
Thank you !

The Square Wave Generator is a little quirky when operating outside of a Single-Cycle Timed Loop, because it needs to ensure that it is called at a rate that will produce the edges of the square wave with precise timing. So it operates similar to a loop timer, in that it blocks execution until it is ready to output a high-low or low-high transition. See the example at examples\R Series\FPGA Fundamentals\Analysis and Control\Square Wave Generator\Square Wave Generator (FPGA).vi for more information.

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!
I'm trying to have an analog square wave input determine where data gathered from a second analog input channel is stored. I want data to be stored to one array during the high signal period of the square wave and data to be store to another array during the low signal period of the square wave. The square wave I'm using is of constant frequency (8.3 Hz). I believe I need to use an analog input wave as opposed to a onboard clock or other timing mechanism because my square wave is also being used to modify the input going into my experimental setup. Thus the data storage needs to be correlated to the timing of the data modification in the experiment. I tried to use the retriggerable property node function, but receive error 200452, which I think means that my PXI card (6115) can't support this retriggerable function. So I'm looking for other ways to accomplish alternating data storage in response to an incoming analog square wave. Any help would be GREATLY appreciated... Thanks! (I'm also quite new with LabView so toddler-type explanations would probably be most useful )
-Shari
(LabView version 8.6)
Attachments:
Pulsed_Acq_Switch_Simplified.vi ‏47 KB

Hello Shari,
I am looking at your situation and it seems very intriguing. after downloading your file I have a couple questions to ask if you don't mind answering.
Currently in your program you are only taking one sample of data at a time, this could lead to uneven sampling. Would you like to sample at a consistent rate (say 10 Kilosamples of data a second?) if so what type of card are you using?
Also, Do you want your data to be in a 2-D array of data?
Best Wishes,
Daniel

I have transefer function like (1/(s^2+s+5)) and i have a square wave input , i want to use this transfer function with this input to see the output , how can i do that , with example please.

i need to know also how to represent this transfer function in labview, try to send me example. answer me at my mail

"st" wrote:
> answer me at my mail
give a valid e-mail first, and your name, we don't like to help anonymous
people
> try to send me example.
how much do you pay ?
> i have transefer function like (1/(s^2+s+5)) and i have a square wave
> input , i want to use this transfer function with this input to see
> the output , how can i do that
First you have to know what you are doing, like an engineer : you have a
Laplace, continuous time transfer function but LabView handles discrete
signals only. Use matlab/simulink if you want to simulate continuous time
systems easily...
If you definitely want to use LabView, the first step is to discretize your
continuous-time transfer function, i.e. decide a sampling rate and convert
it to a "z transfor
m". Then you can directly use the "IIR Filter.vi" as I
said earlier.
Philippe Guglielmetti - www.dynabits.com me at my mail

IMac -- Compatible with UPS Square Wave Voltage

I have been reading of the incompatibility of UPS square wave outputs of UPS devices and the new energy star 4 or 5 computers. The new iMac is energy star-5 compliant. The power supply output of a UPS will not work with new computers.
Does anyone have any information on this issue?

I’ve been trying to find the same answers for my 24”, intel,Core 2 Duo extrerme, 2.8GHXZ, iMac (mid 2007) that Apple Engineering says has Active Power Factor Correction power supply.
All I want from an UPS is decent time to unmount my external H.D., save my working data, and shut down the iMac properly. After the better part of two weeks I believeI have found the answer for my situation. Disclimer: I am not a tech nor experienced in electrical matters but just a guy who hung in there trying to make sense out of many conflicting bits of information. This is not meant to tell you what you should or should not do. Just what I believe I’ve found and what I have done about it
after talking to lots of tech people. Corrections/updates welcomed!
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Duty cycle two AO signals with a square wave

Hello,
I am running two devices with sending two AO signals (sine wave) out simultanously in my code. I need to duty cycle my signals. in other words, I want to turn ON and OFF the devices continously.In order to do that, I am using a square wave generator with 50% duty cycle. The devices should be running when the square wave has positive values and should be OFF when it is negative.
The code almost does that, but it does not seem to be as fast as it is supposed to, based on the square wave's frequency. I was wondering if anyone can help me with this problem. In addition, I am not sure if this is the best method to do that, please let me know if there is a better way. I also attached the VI .
Thanks,
Pooya
Solved!
Go to Solution.
Attachments:
2AOsignal_dutycycle.vi ‏47 KB

I am using NI-PCI 6071E with BNC 2120as an interface. I am not sure if the problem is the hardware limits. Attahced please find the subvis which I used in my main VI.
one of the which has a for loop (duty_cycle.vi) works just fine and the other one (duty_cycle(new).vi), which is the one I am using in my VI, does not. Any thoughts?
Attachments:
duty_cycle (New).vi ‏23 KB
duty_cycle.vi ‏25 KB

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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Thanks

Hello,
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Regards,
Aaron B.
National Instruments

Biphasic square wave with interpulsation intervals

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