Finding amplitude drop from a signal

[Jick]

Hi,

I need to find the amplitude drop from my signal. See attachments. In my jpg picture there is marked the drop place which should be found somehow calculated. Vi has the data.

It is pretty easy to find the higher point amplitude by using trigger detection (at 3,4 for both rising and falling edges for example) and calculate the mean from the data between those points. But how to find the lower point ??

Br,
Jick

[Bob_Schor]

Even without looking at your picture, what you seem to be looking for is where the derivative of your signal is large and negative (i.e. where it is falling quickly).  Now, looking at your picture, what you illustrate is where the first difference (y(i+1) - y(i)) is large and negative.  Fortunately, the "noise" (variability) in your signal seems small compared to the amplitude drop, so something as simple as forming an array of first differences and looking for a minimum bigger than some criterion that you define would seem to work.

Bob Schor

[Jick]

Hi,

Thanks for your reply. Here is something what I tried. It is still hard to catch the lower point because there is no much data between the triggered falling edge and the lower point... If I calculate y(i+1) - y(i) from whole data it is even harder to find the lower point. Any ideas?

Br,

Jick

[JonasM]

Hi Jick,

I might have misunderstood you completely. But I took a look at your code and I can see that you find the high mean value between the rising and falling edge. I also found the lower edge without actually doing anything to your code rather than using the falling edge index and read that index from the array and show that in an indicator. I also made Max Min calculation from the between trigger data. Although I think the trigger value is more correct. But the max is probably better for the max value. If you are interested in the mean then that would be better.

Is this what you want to do?

[Bob_Schor]

You didn't understand what I meant by First Difference.  Look at this -- it is a Snippet, so you should be able to run it, and if not, you should be able to modify your own code to match thisl

Bob Schor