Micromod Micro-DCI: 53SL5100B Single Loop Controller - Manual (Page 51)

53SL5100B Single-Loop Controller
INSTRUCTION MANUAL
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6 ANALOG BACKUP CONTROLLER
6.1 Analog Backup Controller Operation Overview
The Analog Backup Controller is used in operations where a remote computer is normally controlling the
final element directly. In this process configuration, the controller functions as a signal selector and automatic
backup unit to the computer. The controller assumes process control in the event of a signaled computer
failure. The Analog Backup Process Configuration is illustrated in Figure 6-1.
Figure 6-1. Analog Backup Process Loop
The Analog Backup Controller operates as a Single Loop (PID) Controller (see Section 5) when driving the
process final element. While in backup and automatic, the controller continually adjusts its output to match the
feedback signal from the final element (Analog Input 1) so that transfer to on-line operation is bumpless in the
event of computer failure.
Selection of the computer or backup controller signals to the process final element is performed by the
controller’s CCO modules (CCO0 and CCO1) in conjunction with blocking diodes (see circuit diagram of gray-
tone area equivalent in Figure 6-1).
The computer drives the final process element when remote operation is selected at the controller front panel
via the R/L push button and if CClO’s contact is closed; otherwise, the computer’s control signal is diverted
and the controller is active. ANO0 drives the process final element (20 mA computer / 4 mA controller) when
backup control is active.