This instrument only needs to use 220V power supply, avoiding the need for 380V external power supply like conventional equipment. Before testing, only need to set the maximum test voltage, maximum secondary test current and current step, and the instrument will automatically boost the voltage. After the test is completed, the volt-ampere characteristic curve of the tested product is automatically displayed, and 5% or 10% or any electrical error curve can be set, without manual voltage adjustment, manual recording, sorting, and tracing of the curve. This instrument is simple to operate, and it is displayed in Chinese without special training, and it is easy to master.