CWT-S1-4G Work with Scada Modbus Rtu to Tcp 4G Gateway

How does Scada system read and write Modbus slave over 4G?

Usually, SCADA cannot directly send Modbus message to 4G gateway, because 4G network does not provide static public IP address for simcard (except VPN), For dealing with this issue, CWT provide a Modbus TCP to RTU tool to work with Scada in server，it converts SCADA Modbus TCP to RTU message and send to 4g gateway, then 4g gateway forward Modbus RTU message to Modbus slave on RS485, So that realizes the connectivity of SCADA and remote Modbus slave over 4G.

Communication process:

1). CWT 4g gateway build TCP connection with Modbus TCP to RTU toolaccording to server IP address (in this case, static public IP address or domain is necessary for server)

2). Scada system send Modbus TCP command to Modbus TCP to RTU toolaccording to salve ID (in this case, remote RS485 slave is treat as a TCP slave)

3). Modbus TCP to RTU tool convert Modbus TCP to RTU message and send to 4g gateway

4). CWT 4g gateway forward the Modbus RTU message to Modbus slave on RS485.

5). The responds message of Modbus slave is sent to Scada in same way.

Set gateway by config tool

It’s Modbus TCP to RTU tool that run with Scada in server. After 4G gateway connect up, show the connection.

Test by Modbus poll

For example, 4G gateway connect a temperature humidity sensor on RS485, Run the Modbus poll in server to read the sensor.

Modbus poll connection is shown in Modbus TCP to RTU tool

Specifications

Size Diagram

Package list

gateway×1, antenna×1，USB cable×1