How to make a variable amplitude of a waveform and then get its derivative?

[Cyrille09]

Hi guys. I'm new in NI Labview so i really need your help. I'm working on a program that gets the derivative of a continuous signal. I want to make the amplitude to be adjustable depending on what the user wants. In determining the amplitude of my waveform, i will use two controls and multiply their values and the product will define the amplitude of my waveform. But when i try to do that, the output waveform(which is differentiated) becomes a stratight line or zero. I believe there is something that i am missing for this to work. I hope you can help me.

[Bob_Schor]

Your waveform is a triangle waveform.  Over the rising phase, the derivative is the (constant) slope, and over the falling phase, the derivative is also the (constant, but negative) slope.  The derivative should therefore be a square wave.  This is what your program provides.  Note that if you use the "canned" derivative function that LabVIEW provides (which you did), you need to understand what it is doing to interpret the (not-quite square wave) output it produces.

In short, your program seems to be working perfectly.

Bob Schor

[TYtanic]

Hey Cyrille,

Was the attached VI that you provided an example of the issue that you were experiencing, or was it an example of your working program before you tried to implement the "two controls for amplitude"?

I agree with Bob that your VI is working correctly, but that VI doesn't seem to be what you were describing in your post. Please respond if you have any more questions!