ControlMaster CM30, CM50 and CMF310
Universal process controllers,
1
/
4
,
1
/
2
DIN and fieldmount
8 Templates and Functionality
90
IM/CM/ED–EN Rev. X
8.2.2 Analog Backup Station (Low Signal Selection / Digital Signal Selection)
This template provides a back up for a master controller (system). In normal operating mode, the
ControlMaster operates in Remote Control Mode. In this mode the output of the ControlMaster follows the
Master controller's output. If a fault is detected in the Master system, either by a low signal on the Master
output or by a digital input, the ControlMaster switches into Local Control Mode and the process is
controlled by the PID output of the ControlMaster.
The PID algorithm continuously tracks the Master Controller output value to ensure a bumpless transfer
from remote to local operation. Once the Master Controller output is restored or the digital Input returns to
its normal state the ControlMaster switches back to Remote Control Mode and continues to track the
master Controller.
(See Fig. 8.1, page 91 for details of parallel connection).
AIN 1
AIN 2
1
Low Signal Selection
2
Digital Signal Selection
1
2
DIN 1
Alarm 1
Manual
Output
AO1
PV
Loop 1
PID Control
L/R
A/M
SP
PID
O/P
Local Set
Point
LSPT1
LSPT2
LSPT3
LSPT4
Master Output