The Ruler lets you measure horizontal distances on the plot. The ruler acts as an overlay, with a pair of vertical cursors passing through its two holes. These are intersected by an horizontal cursor, which records the current height. You can use the horizontal and vertical cursors to precisely position the ruler (or you can just click-and-drag the ruler itself, to move it around the screen).
Do one of the following:
Click the Ruler button in the Toolbar.
Choose: View > Overlays > Show/Hide Ruler.
Do one of the following:
Click and drag the ruler with the mouse.
Click-and-drag a vertical (red or green dashed lines) or horizontal (blue dashed line) cursor to precisely position the ruler.
Right-click on the ruler and choose: Copy from the contextual menu.
Follow these steps:
Adjust the plot scale so that the peak to be measured fills the screen.
Position the ruler's horizontal cursor at the top of the peak. (You may need to slide the ruler to one side, so you can clearly identify the peak top.)
Right-click on the ruler and choose: Move Down 50%. The ruler moves vertically downwards to half the peak maximum.
Click and drag the ruler's vertical cursors (red and green dashed lines) so that they intersect the peak on each side of the ruler.
The Full Width at Half Maximum (FWHM) is displayed in the ruler.
Follow these steps:
Use the ruler's left- and right-cursor to specify your chosen x-axis limits.
Position the ruler's horizontal cursor to specify your chosen y-axis maximum limit
Right-click on the ruler and choose: Zoom to Cursors. The plot will be redrawn with your limits applied.
See Also