Two harmonic signals with time difference to one modulated signal

[aj109]

Hi LabView experts,

I'm not realy good in using lab view, but I need the visualisation for my diploma thesis.

I know how to creat a sin wave and I know how to creat a modluated signal out of to different sin waves.

but I want to creat a modulated signal where the HF signal is starting later.

So first you have the low frequency sin wave and maybe after one sec. the high frequency signal will be modluated on top.

It would be great if someone could tell me how to do that.

unfortunately I'm using labview 7.1 so I will not be able to open newer files.. 😞

thank you very much!!

[Ray.R]

"I know how to creat a sin wave and I know how to creat a modluated signal out of to different sin waves.

but I want to creat a modulated signal where the HF signal is starting later."

Are you simulating all these signals within Labview?  I suspect you do. 

"So first you have the low frequency sin wave and maybe after one sec. the high frequency signal will be modluated on top."

So are you trying to see the sine wave on a graph, then 1 sec later introduce the HF signal and then you'll see a modulated signal on a graph? 

I don't fully understand what you are trying to do.  Can you provide a bit more description?

Where do you have a problem with introducing a signal 1 sec later?  And why is this a constraint?

RayR

[aj109]

Hi RayR,

thank you for your quick answer.

you are right. that is what I want to do! 

I want to simulate a modulated signal. but i want to show how it looks like when the modulation is not starting at t=0.

I attached a draft   i hope that can help.

but the problem is, that I do not know how to tell the software, that the modulation should sart later.

Greetings from Germany

Josef

[MikeS81]

Hi Josef,

your picture is empty.

Mike

[aj109]

hmm thats strange..

i created a pdf so now it should work..

Josef

[Ray.R]

As Mike said, the picture is empty.

There are many ways to approach this.  The architecture may depend on how you interface with the software (User Interface) and the level of interaction with it.  After saying that, I am thinking of Architectures, such as Event Structures, Producer/Consumer Loops, State Machines..   Maybe a State Machine could do the trick..  However, before suggesting something, I have a question.

Can the modulator portion of the code receive a frequency of zero (0) while waiting to start the modulation?  So the result would be an un-modulated signal...  And when you activate the HF, you'd end up with the desired modulated signal?

RayR

[aj109]

Hello,

i added my current file.

i think it should be really easy to solve this problem!! 

Josef

[aj109]

Good morning RayR,

can you open my vi?

isn t there a real simpe way to start the modulation?

[Ray.R]

It's a bit long to explain what you did wrong.. 

First thing.. STAY AWAY FROM STACKED SEQUENCES!!!    Sorry for shouting!  But I keep praying that NI will remove those horrible things! 😉

Stacked Sequences are annoying because they make you loose sight of the dataflow that goes on inside the code.  Forcing sequential actions is not a good thing in Labview.

Have a look at the attached code.  It will do what you wanted.  It can still be improved, such as changing the For Loop to a While Loop and have the graph update as run run the VI, instead of a fixed number of iterations.

Let me know how it goes..

RayR

Message Edited by JoeLabView on 06-13-2008 08:43 AM

[aj109]

Good morning RayR

thank you for your response!

It seems like you used LV 8.5. Unfortunately I am using 7.1.. 😞

but i also have a demo version of 8.2.

so it would be nice if you could make a screenshot!

thanks a lot!!!

Josef