Quick Answer:
Short Answer
Mechanical systems use motorized sensor positioners; electronic systems use software feed-forward to adjust guide points without moving parts.
Mechanical Master/Slave (legacy): The Master sensor is mounted on a motorized slide that physically chases the web position. The Slave sensor is mechanically linked to move the same distance. This creates wear parts, lag, and "loop within a loop" tuning problems.
Electronic Master/Slave (Roll-2-Roll Technologies): Both sensors connect to a single controller. The controller reads the Master position and electronically adjusts the Slave guide point in real-time—no physical sensor movement. This eliminates mechanical lag, wear parts, and tuning instability.
The electronic approach also enables capabilities impossible with mechanical systems, such as centerline matching between webs of different widths.