Which component is often chosen for an easy-to-install magnetic sensing solution with a normally open output?

• A. Hall effect sensor
• B. Magnetic reed switch
• C. Photoelectric sensor
• D. Proximity sensor

Answer: (B)

The main idea here is using a simple, magnetically actuated switch that requires no power to operate and provides a normally open contact. A magnetic reed switch fits this perfectly: it contains two ferromagnetic reeds sealed in a glass envelope. When a magnet is brought near, the reeds attract and close the contacts, completing the circuit. In the absence of a magnet, the contacts stay open, which is exactly what “normally open” means. It’s easy to install because you literally place the switch where you want sensing and bring a magnet to switch it, with no power needed to operate the device. It’s also compact, low-cost, and well-sealed for rugged environments.

Other options add steps or require power: Hall effect sensors are active devices that need power and provide electronic outputs, which is more setup than a simple switch; photoelectric sensors rely on light beams and are not magnetic in nature; proximity sensors are powered devices that detect presence without physical contact but involve wiring and electronics beyond a basic magnetic contact.