Internet-based Data Transmission for Pipeline Monitoring

Related Vendors

DÜPERTHAL Sicherheitstechnik GmbH & Co. KG

TURCK GmbH

EagleBurgmann Germany GmbH & Co. KG

PHOENIX CONTACT Deutschland GmbH

Precise Time Stamp in the Millisecond Range

In the case of the Taiwanese project, two requirements were at the forefront:

• On the one hand, the measured value should be transmitted via a precise time stamp in the millisecond range.

• Furthermore, two systems, namely the controller installed in the field and the server, were securely connected with each other via the Internet.

The system time of a small-scale controller includes only hours, minutes, and seconds as standard. The millisecond range is thus not provided, yet it can be generated by using cyclical tasks within the scope of an application program. Since all stations need to be synchronized, connection to an atomic clock-based system was inevitable. The corresponding Network Time Protocol (NTP) is available free of charge to each user on the Internet.

Nevertheless, runtimes through the Internet for gathering this time can influence precision, meaning that use of an NTP server service combined with in-house hardware represents the more precise solution. This approach compensates the runtimes through the Internet and eradicates any errors. The mGuard RS 2000 security router from Phoenix Contact offers, for example, the NTP server service.

At the same time, the device establishes Ethernet connection with the server via the Internet using a secured VPN tunnel (Virtual Private Network). The VPN tunnel enables direct communication between the controller and the Pipe-Control server, as if the two were connected by Ethernet cable. In doing so, the tunnel is installed with two mGuard routers, which ensure secure transmission. The controller and server exchange their data via Modbus/TCP, which is why an Ethernet connection is required as a communication medium. The PLC in the field acts as a Modbus server here. The Pipe-Patrol server collects measured values, which the controller currently provides at any time with a time stamp.

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