Hach SC1500 Bedienungsanleitung Seite 19

Modbus TCP/IP expansion
Modbus TCP/IP is a standard for industrial communications. The Modbus TCP/IP protocol connects
computers to measurement and control systems that use the TCP/IP protocol for data transmission.
This type of data transmission is known as machine to machine (M2M) communication.
The Modbus TCP/IP software module enables the controller to be integrated directly in
programmable logic controller (PLC) systems. PLC systems record and process the controller
measured data. The data analysis and the procedures caused by the results are programmed in the
PLC system.
Note: To use the Modbus TCP/IP software module, make sure that there is no Modbus card installed on the
controller.
Connect the controller to the external USB box. Refer to the documentation supplied with the USB
box. It is possible to daisy chain controllers. Refer to Figure 12. When a modem or WiFi stick is
connected at the USB box, this channel connects the controller to the internet. Thus, it is not possible
to connect the controller with the modem to the internet and to operate Modbus TCP with WiFi at the
same time; the USB box has only one USB slot. In such situation, Modbus TCP/IP can only operate
with the ethernet LAN connector (ethernet M12 connector). Table 7 shows the Internet and Modbus
TCP/IP possible connections combinations.
When only one controller is used, only the right M12 connector is used to connect to the PLC/internet
(left connector is not used). When daisy chain is used, always connect the right M12 connector with
the left M12 connector of the next controller. The daisy chained controller connected to PLC/internet
uses the right M12 connector for PLC/internet connection.
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