Limit switches should be adjusted so the contacts actuate at the point where the actuator stop is located or slightly before.

• A. At the point where the actuator stop is located or slightly before.
• B. Before the actuator stop.
• C. After the actuator stop.
• D. At any arbitrary point along travel.

Answer: (A)

Limit switches define the end of travel, signaling the controller to stop the motion at the intended position. Setting the switch to actuate when the moving part reaches the actuator stop, or slightly before, gives a clear, timely stop signal. The slight lead before the end accounts for inertia, accelerator/decelerator time, and mechanical play, so the machine reaches the end position cleanly without slamming into the stop. If the switch tripped after the stop, the mechanism could overshoot and cause damage; if it tripped too early, the travel would end short of the desired position. An actuation point near the end of travel provides reliable stopping and accurate positioning.