... power supply before operating,when the power supply is DC voltage,positive and negative can not be connected wronging,or it will ... ,above 500V should concect the current transformerXXX/100V.4.Frequency meter , sampling AC voltage signal input value,(110V-380V), i.e. display the ... digit 3.Sampling speed: about 2.5 times/sec 4.Temperature: 0∼40 5.Watt-loss≤2VA 6.Maximum input AC voltage: 500V