Which device is used to determine rpm in rotating equipment?

Which device is used to determine rpm in rotating equipment?

• A. Tachometer/strobe light
• B. Hygrometer
• C. Thermometer
• D. Voltmeter

Answer: (A)

When you need to know how fast a rotating piece of equipment is turning, you’re looking for revolutions per minute. A tachometer is built for that purpose and gives a direct readout of rpm. A strobe light often accompanies a tachometer: by flashing at a rate that matches the shaft’s rotation, the moving part can appear stationary, letting you infer rpm from the flash rate (rpm ≈ flash rate in cycles per second × 60). The other instruments measure humidity, temperature, or voltage, which don’t tell you how fast the shaft is turning.

When you need to know how fast a rotating piece of equipment is turning, you’re looking for revolutions per minute. A tachometer is built for that purpose and gives a direct readout of rpm. A strobe light often accompanies a tachometer: by flashing at a rate that matches the shaft’s rotation, the moving part can appear stationary, letting you infer rpm from the flash rate (rpm ≈ flash rate in cycles per second × 60). The other instruments measure humidity, temperature, or voltage, which don’t tell you how fast the shaft is turning.