DIGITAL OUTPUT CIRCUIT IN FIELD COMPUTER UNIT AND METHOD FOR NON FORCIBLY TESTING ANALOG OUTPUT CIRCUIT

摘要

PURPOSE: A digital output circuit in a field computer unit and a method for non forcibly testing an analog output circuit are provided to realize a distributed network of triply redundant field computer units which communicate with redundant process control computers to maximize both accuracy and the overall system's tolerance to faults in the process control system that affects the physical process being controlled. CONSTITUTION: A digital output circuit(10) in a field computer unit includes a network of distributed triply redundant input/output field computer units(12). The digital output circuit(10) is capable of utilizing a maximum of sixty four field computer units(12). The redundant process control computers(14) preferably operate concurrently on all of the signals transmitted from the field computer units(12). A preferred form of possible value reconciliation, corresponding output value tables in each of the process control computers(14) is compared during a preset time period, and one of the values is chosen for each output value signal to be transmitted to the field computer units(12). Each of the process control computers(14) preferably include a network controller(16), a debug panel(18) for the network controller, and a tray(20) upon which to support the fiber mount boards(22) to which various fiber optic conduits(24) are connected. The fiber optic network which connects each of the process control computers(14) with each of the field computer units(12) includes a set of breakout circuits(26) for each of the redundant process control computers.