Finding a maximum PIC for a cluster graph

[rdastyle]

Hi everybody,

I am trying to obtain the maximum of a graph which is a cluster of 3 elements. I've red several posts and I found useful answers but not for a graph generated with a cluster.

I would like to put in place a marker at the maximum, i.e. at X max and Y max. I managed to obtain the Y max but I had to do it not on the graph but on the Y array.

Actually, on the printscreen, you can see my diagram.

Any idea ?

Thanks.

[rdastyle]

I found this on a previous forum :

http://forums.ni.com/t5/LabVIEW/how-to-convert-cluster-to-waveform/td-p/432030

Which explains how to convert a cluster graph (waveform) into a " classic " waveform. Thanks to this, I could do a pic detection BUT it does not work for me. The " classic " waveform does not match the cluster graph (waveform) at all.

Any idea ?

Thanks. 

[rdastyle]

Ok, I have almost reached my goal : now I try to obtain EXACTLY the same graph. (see Diagramv2 and FaceAvantv2).

The left one is correct and the right one has diffrent values for X axis and I don't understand why.

Any idea ?

Thanks.

[smercurio_fc]

I'm a little confused. Are you trying to find the peak programmatically, or use a cursor? Your first post seemed to imply that you were trying to do it programmatically using the Peak Detector VI. Your error was that you were wiring the cluster. You should have just wired the Y array directly to the Peak Detector VI.

[rdastyle]

Hi and thanks for your answer.

Actually, I am using a spectrum analyser. I found the way to see the graph in LabVIEW and my goal was to calculate, thanks to the graph in LabVIEW ; the maximum of the curve.

I found a solution (see the attached picture) but I was wrong for the beginning : the spectrum analyser gives a curve with frequencies and I tried to use a " classic " graph to make the convertion between a cluster graph (obtained with the LabVIEW's VI from the analyser).

Using Vis from signal procesing solved my trouble. In my case, the trace array is my amplitude, the " -10 " is my threshold for the detection of my pic ; under this value, no pic is detected. The " X increment " is my pitch and the " Initial X " is the first value of my range of X.

To conclude, I've got a graph with, on X axis a frequency started from 818 MHz (8,18E+8 Hz) to 918 MHz (9,18E+8 Hz) which is my bandwidth. On Y axis, I have my amplitude. I managed to obtain the maximum of my curve with the VI " Peak detector " and NOT with using a convertion of my cluster graph instead of this convertion seems to work well with others curves.

Thanks.