Hi Mimmo
It can be as simple or as complicated as you want.
To learn Plus1 the simple way would be to make a fixed scale bargraph.
First, find the (x,y) coordinates for both the beginning and end of the bar.
Then Scale the input from x-start to x-end, or y if you want a vertical bargraph.
Connect those scaled values to a line in the design editor, and you have a working bargraph.
/Jakob