Which instrument is used to verify the direction of alternating current phases in a multi-phase electrical system?

• A. Home electricity tester
• B. Phase rotation meter
• C. Voltage tester
• D. Ohmmeter

Answer: (B)

Determining the direction of the three-phase voltages—whether the sequence is A-B-C or A-C-B—requires an instrument that reveals the order in which the phases appear. That’s exactly what a phase rotation meter does. By applying the three-phase voltages to its inputs, it shows the rotation direction (which sequence the phases follow). This is essential for devices like motors, where the rotation direction depends on the phase order; if the sequence is wrong, swapping two leads will change the direction and correct the motor’s rotation.

Other tools don’t provide this information. A home electricity tester or a simple voltage tester checks for voltage presence or polarity but not the phase order. An ohmmeter measures resistance, not the sequence of voltages. So the phase rotation meter is the tool designed to verify phase direction in a multi-phase system.