The digital AC voltage, current, and frequency are displayed simultaneously on the meter. The meter does not require an additional power supply or transformer. It includes 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 features a 15mm hole diameter, compatible with standard 21-25 square millimeter copper wire. Voltage range: AC 50-500V. Current range: AC 0-120A. Frequency range: 10-99.9Hz. Hole size: 68x68mm for embedded installation. Measurement accuracy: 1%. Display: 2-digit. Color: Black. Material: ABS. Dimensions: 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.