Pzem016Test
The PZEM-014/016 can measure Ac voltage V, current A, active power W, frequency Hz, power factor pf and used energy Wh. You can read all these values from the PZEM with the help of a Rs-485 Half duplex bus. The protocol they used is the well known modbus protocol.
For more info: http://evertdekker.com/?p=1307