find the starting point of wave in a waveform

[ig31]

Hello, my name is Titi. I am a beginner in labview programming. I have a problem when i try to find the value near the wave. I want to know how to find the starting point (they called onset time of waves).   as u see in this figure, there is a red signal. i want to detect the starting point (onset time) of three waves (black, purple and blue cursors). Thank you..  

[GerdW]

Hi titi,

as that red curve seems to stay at zero for the most time you could simply compare the red values with a certain limit. Whenever the limit is crossed the first time you will have the "start of the wave"…

[ig31]

yes, i have tried to compare the value, if the value greater than initial value, then i'll plot it as starting point.. but, i could not plot the cursor as in figure..

when i try to plot the position in the right place, i doesn't work, because always show Y value. I want to show X and Y value so that the value will move to the right position..

[altenbach]

---

@ig31 wrote:

yes, i have tried to compare the value, if the value greater than initial value, then i'll plot it as starting point.. but, i could not plot the cursor as in figure..

when i try to plot the position in the right place, i doesn't work, because always show Y value. I want to show X and Y value so that the value will move to the right position..

---

Posting a code picture full of local variables, right-to-left wires, hidden code, and race conditions does not help us to solve the problem. Clean up the code and attach the actual VI and some data. Where are the terminals? Does it matter if the right and left disconnected code fragments execute in a certain order? If you autoindex on a FOR loop, you don't need to wire N. Why do you think you need to read the exact same local variable twice in parallel? Are you expecting different results? The "active cursor" and "cursor posx" property nodes can be combined into one.

I strongly recommend to do a few more beginner tutorial before proceeding.

[ig31]

yes, my problem is my teacher assist me to modified the program from previous developer. so i have to continue his work.. can u give a simle example, how to do that and i may learn from your suggestion. Thank you

[adena.l]

Hi ig31,

Are you able to post your VI so that people on the forums can get a better idea of your code architecture? 

[ig31]

yes, this is the vi file.. i want to detect the reg signal at the first waveform (sEMG). As u see, there are 2 signals in that waveform (blue and red signals).