Distributed measurement and control system for industrial processes

摘要

The disclosed invention includes at least one programmable industrial measurement and control device operable in a stand-alone mode to sequentially and repetitively sample a plurality of analog input channels and store in preselected memory locations digital data representative of corresponding channels, to repetitively evaluate a predetermined plurality of industrial measurement and control functions on said data, and to actuate selected output channels in accordance with the results of each of the evaluation iterations to provide real-time control of an industrial process. Means including a pointer controlled ROM work list, a ROM program directory, a ROM variables control, a RAM report control, a RAM function control, and a ROM program code table specify the time sequence of, and the data and control structures for, each evaluation iteration. A host system is connected to the devices via a local area network for operation in a shared resources mode, and may be either a processor or an interactive terminal. The local area network includes two shielded twisted wire cables. A CSMA/CD communications protocol is implemented. Gateways connect the host to the network, and connect peripheral devices such as printers or graphics displays to the network. In the shared resources mode, each node on the network may routinely prepare and send reports to the host representative of sensed industrial conditions, may respond to host system generated commands, and may prepare and send exception reports to the host system whenever the industrial process exceeds prescribed bounds.