The digital AC voltage, current and frequency are displayed on the same meter at the same time. The meter does not need to add power supply and transformer. The meter comes with a 120A precision small transformer. This instrument is only suitable for pure AC 50-60HZ mains power supply. It cannot be used for square wave, inverter output, and sine wave circuits with modified sine waves, otherwise the instrument will be permanently damaged 120A transformer (hole diameter 15mm) can meet standard 21-25 square millimeter standard copper wire through. Voltage: AC50-500V Current: AC0-120A Frequency: 10-99.9Hz Hole size: 68x68mm (embedded installation) Measurement accuracy: 1%2 words Colour:black Material:ABS Size:72 x 72 x 32mm Package Contents: 1 x measuring instrument Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.