Closed loop poles and zeros Plot
To get the gain at a point on the rootlocus, click on the 'Measure' button. You will then be prompted to click on a point on the rootlocus. If the point that you selected lies on the rootlocus, the gain will be displayed on the rootlocus window (for *nix users, the display position is on the top, for Windows users, the display position is on the bottom left corner).
Changes to the rootlocus can be made at the click of a mouse by using the 'Plant' button. You may add/remove a pole/zero / edit the plant by typing in the required transfer function.
The default gain of rootlocus is 1000. This can be changed by changing the gain in 'Settings->Root Locus'. You can choose gain to be either in the forward or feedback path. The default configuration is the so called standard 'control loop with a plant, gain, controller and sensor. Gain configuration can be changed in 'Settings-->Gain configuration.' There is a choice of Grid On/Off ('Grid' button). You can plot damping ratio and Natural frequency lines using the 'Grid->zeta/wn' option.
Manipulation of the rootlocus can also be done using the 'Control Center' window which has the same menu structure as the Rltool Main Window. The maximum gain of the rootlocus plot can also ' be changed in the 'Control Center' using a drop' down box that has fixed maxium gains of 100, 500, etc