Wago - 4PU & 4PS - 28
Appendix 3 - Modbus
A3.1 Communication via Modbus
The energy meter can communicate with the PC and other Modbus master devices. To read out the meter registers, first install
and configure the PC software. Use an RS485 to USB converter to connect the PC and the meter. The cable is connected to
terminals 7 and 8.
The following are the factory set Modbus parameters:
•
Modbus addresse 001
•
Baud rate 9600
•
8 data bits
•
Even parity
•
1 stop bit
The baud rate can be changed to values 115200, 56700, 38400, 9600, 4800, 2400, 1200, 600 and 300.
The parity can be set to none or odd. Data and stopbit cannot be changed.
4PU:
4PS:
When connecting the meter through a serial converter (RS485) for testing, please be aware that because of not implementing the
complete Modbus infrastructure, there will be a need to put an additional resistor (120 ohms/ 0,25 watts) across the terminals
(7 & 8) on the meter side.
For the registers used in the meter and how to interpreted the data, please use the Modbus register map on the next pages.
More information on Modbus can be found:
Physical:
http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
Protocol:
http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf
