generate a signal point by point from a formula

[HungChu]

Hi everyone,

Im new to Labview and im learning to use it for my DSP course. I have been trying to find a way to generate a signal point by point from a formula but it seems i cant find it.

Does anybody have any idea about it?

Regards,

Hung Chu

[Fuzzy Me]

Try using function

\Program Files\National Instruments\LabVIEW 2010\vi.lib\measure\masignal.llb\Sine Waveform.vi

At output you will be getting a start time to, delta t and corresponding all y vaules. From this you can build the two array of t (time) and corresponding Y

[HungChu]

Thanks Fuzzy,

But I mean from a specific formula to generate a point by point signal. In my case the formula is cos(wt)exp(-(t^2)/(T^2))

T and w can be set to be a constant.

[smercurio_fc]

All you need to do is to generate the array of t values. This can be done a variety of ways. You could use a loop, or you could use one the many signal generation functions, depending on what t is suppose to be. It may be that the simple Ramp Pattern will suffice to give you the required array of t values. Then just wire up the array through a bunch of primitives to get your formula.

For example:

[HungChu]

Thanks smercurio_fc,

But I dont know if this is a correct way of generating signal point by point. Since it will generate a whole waveform just like the "waveform generation : formula waveform.vi".

I want to generate it point by point because I want to FFT it point by point ( it's like a moving graph).

[smercurio_fc]

Then simply auto-index a for-loop and put your FFT pt-by-pt inside the for-loop.

[HungChu]

It showed me the result instantly. It's not like point by point.

My real onjectives are getting the signal point by point then FFT it every time a point is acquired so I think the graph should be continuing to move until i stop it.

[smercurio_fc]

Then put a delay in the loop so you can see it "point by point". It's doing it point by point, but it's so fast that it appears to you that it's not.