During a fire pump test, which instrument is used to measure rotational speed?

During a fire pump test, which instrument is used to measure rotational speed?

• A. Calibrator
• B. Multimeter
• C. Refractometer
• D. Tachometer

Answer: (D)

Measuring rotational speed directly requires a tachometer. In a fire pump test, knowing how fast the pump shaft is turning (in revolutions per minute) is essential because the pump’s performance, head, and flow are all tied to that speed. A tachometer can read the shaft speed directly, whether by contact with the rotating surface or by non-contact infrared/laser methods, giving an immediate RPM value to verify that the motor is running at its rated speed. The other instruments serve different purposes: a calibrator checks and adjusts the accuracy of measurement devices, a multimeter measures electrical properties like voltage and current (not rotation), and a refractometer measures the refractive index of liquids (not anything to do with shaft speed).

Measuring rotational speed directly requires a tachometer. In a fire pump test, knowing how fast the pump shaft is turning (in revolutions per minute) is essential because the pump’s performance, head, and flow are all tied to that speed. A tachometer can read the shaft speed directly, whether by contact with the rotating surface or by non-contact infrared/laser methods, giving an immediate RPM value to verify that the motor is running at its rated speed. The other instruments serve different purposes: a calibrator checks and adjusts the accuracy of measurement devices, a multimeter measures electrical properties like voltage and current (not rotation), and a refractometer measures the refractive index of liquids (not anything to do with shaft speed).