Assessing The Integrity Of Field Devices In Modbus Networks

Pipeline control systems often incorporate thousands of widely dispersed sensors and actuators, many of them in remote locations. Information about the operational aspects (functionality) and integrity (state) of these field devices is critical because they perform vital measurement and control functions. This paper describes a distributed scanner for remotely verifying the functionality and state of field devices in Modbus networks. The scanner is designed for the Modbus protocol and, therefore, accommodates the delicate TCP/IP stacks of field devices. Furthermore, field device scanning and data storage and retrieval operations are scheduled so as not to impact normal pipeline control operations. Experimental results and simulations demonstrate that the distributed scanner is scalable, distributable and operates satisfactorily in low bandwidth networks.