Industrial Lan Using Distributed Microprocessors

Abstract

The objective of this work was to design and implement a local area computer communication network (LAN) to support computerized monitoring of production equipment in an industrial plant. The network was estimated to consist of 200 microprocessor data acquisition units (nodes) monitoring a total of 10,000 sensors (an average of 50 sensors per node) and a central host minicomputer. The maximum distance between nodes would not exceed one kilometer. If the transmission media required repeaters or regenerators, the minimum distance before they would be required would be one kilometer. Communication would primarily occur between the host minicomputer and the nodes. There would be minimal communication between the nodes themselves. The network was to be fault tolerant and was to continue operating in the event of a single point failure such as a transmission line breaking or node failure. The network was to consist of interconnected segments where the failure of any segment would not affect other segments. The typical message size was estimated to be 10 bytes consisting of an identification of a sensor, the time of change in condition of the sensor (occurrence or clearing of a fault) and the time of occurrence. Longer messages of approximatly 100 bytes consisting of parameter tables describing sensors and data base information, would be infrequently transmitted (whenever a node was powered up). The message traffic would typically be short bursts of an average of 10 messages per minute but with peak bursts of 10,000 (in event of power failure of entire plant). The transmission media must operate reliably under extreme electromagnetic noise conditions with a maximum bit error rate of 10^-6. The bandwidth was to be minimally 2 MHz because the nodes could transmit at a maximum rate of 2 MHz. The network was to require a relatively low level of technical expertise for maintenance.