🔍 Key Concepts

• Relationship between rotational speed (RPM) and frequency/voltage produced by certain electrical devices • How a tachometer generator (tach-gen) or small permanent magnet generator can be used to sense speed • Which listed devices are actually used to produce a voltage signal proportional to shaft speed

💭 Think About

• Which of these options is specifically designed to produce an electrical output that varies directly with shaft RPM? • For an engine room console indicator, what kind of device would be mechanically coupled to the shaft or motor and electrically wired to the console? • Which devices in the list are realistic in a marine propulsion control system, and which are obviously used for something else?

✅ Before You Answer

• Identify which option is a speed-sensing generator that outputs voltage proportional to RPM • Eliminate any devices that do not normally produce a voltage signal used for RPM indication on a control console • Confirm that the chosen device can be mechanically driven by the motor shaft and electrically connected to the console indicator