End-of-travel sensing in nonservo traverse systems is most commonly performed with which device?

• A. Proximity switches
• B. Limit switches
• C. Photoelectric sensors
• D. Encoders

Answer: (B)

End-of-travel sensing in a nonservo traverse system relies on a simple, definitive signal that tells the controller the carriage has reached its limit. Limit switches provide exactly that: a mechanical contact or geared switch that is activated right at the defined end position, delivering a clear on/off signal to stop or reverse motion. They are rugged, inexpensive, and easy to mount at precise points along the travel, which makes them the most reliable way to detect limits in a straightforward, non-closed-loop setup.

Proximity switches can sense metal without contact, but their trigger depends on distance and can be less precise at the exact limit, especially if the part isn’t in the correct orientation or if there are surface variations. Photoelectric sensors rely on a light beam and can be disrupted by dust, misalignment, or reflective surfaces, leading to false readings. Encoders give position information, but without a closed-loop drive, they don’t provide a guaranteed end-of-travel signal and add unnecessary complexity for simple limit detection.

So, limit switches are the most practical and dependable choice for end-of-travel sensing in nonservo traverse systems.