The digital AC voltage, current, and frequency are displayed simultaneously on the same meter. The meter does not require an external power supply or transformer. It comes with a 120A precision small transformer. This instrument is designed for pure AC 50-60Hz mains power supply only. It is not suitable for use with square wave, inverter output, or modified sine wave circuits, as this may cause permanent damage. The 120A transformer (hole diameter 15mm) accommodates standard 21-25 square millimeter copper wire. Voltage: AC 50-500V. Current: AC 0-120A. Frequency: 10-99.9Hz. Hole size: 68x68mm (for embedded installation). Measurement accuracy: 1%. Display: 2 digits. Color: Black. Material: ABS. Size: 72 x 72 x 32mm. Package includes: 1 x Measuring instrument. Other items not included. Note: Lighting and display differences may cause slight color variations. Measurement error: 1-3cm.