A tachometer is used to monitor the rotational speed of the motor shaft.

• A. True
• B. False
• C. Not applicable
• D. Unknown

Answer: (A)

Measuring rotational speed of the motor shaft is exactly what a tachometer does. A tachometer provides RPM readings that are used to monitor and control how fast the shaft is turning, which is essential for maintaining the desired performance, ensuring safe operation, and enabling feedback in closed-loop motor control. Tachometers can sense speed in several ways—by attaching a sensor to the shaft, using optical or magnetic pickups, or estimating speed from the motor’s back-EMF—and then convert that information into a readable speed value. Because the core function of a tachometer is to monitor shaft speed, the statement is true. The other options don’t fit because they imply the device doesn’t track speed or provide unknown or irrelevant information, which contradicts the actual purpose of a tachometer.