For the direct access line of the watt-hour meter, according to the load voltage and current selection of the appropriate specifications, so that the power meter rated voltage and rated current, equal to or slightly greater than the load voltage or current. In addition, the load of electricity consumption in the Watt-hour meter rating of more than 10%, otherwise the measurement is not allowed. Sometimes even the aluminum plate rotates. So the watt-hour meter can't be chosen too much. It is easy to burn the Watt-hour meter If you choose too little.