... Features: 1) True effective measure: voltage, current, active power, reactive power, power factor, frequency, Kwh, etc. Total 28 electrical parameters; ... power, reactive power, frequency power factor etc., set freely.6) RS232 or RS485 communication, Modbus RTU protocol.7) With power down memory ... function for KWH / KvarH.8) Power supply: 18--30V AC/DC or ...