Abstract: A process control interface system having a network of distributed triply redundant input/output field computer units. The system includes a plurality of self-contained remotely located triply redundant field computer units connected to decision making redundant process control computers through a bi-directional communication network having at least two concurrently active communication channels. Each of the field computer units include a set of at least redundant field computers for arbitrating both input and output signals. The input arbitration method enables a plurality of selectable default input conditions, such as select HIGH and select LOW, in the event that a majority agreement cannot be reached among valid input signals. The output arbitration method includes a plurality of selectable default output conditions, such as fail SAFE and fail LAST. Each of the default input and output conditions may be rapidly adjusted through software selection.
Type:
Grant
Filed:
January 26, 1995
Date of Patent:
October 19, 1999
Assignee:
The Dow Chemical Company
Inventors:
Robert S. Hoy, Timothy J. Grai, Robert J. Hozeska