
5Ć2 Configuration Tips
Original Ć June 1990CE4.2:CL6211
on a secondary form by a PROVUE" selection under the Extra Data"
menu option. There are also secondary forms for UOC and Trend Unit
specific data that is required. These Extra Data" menu selections are
only available if a device of the relevant type appears in the current
group.
Although the group field only displays six devices at a time, the VT220
Prev Screen" and Next Screen" keys allow scrolling through the
complete target device list. Notice that Index" (relative DBI) is specified
individually for each target device.
5.2 Ratio Control
Ratio control is used in continuous applications for blending two or more
ingredients in given proportions. Controller loop points using a station
type which includes RSP (remote set point) as a valid mode may use
ratio control.
When ratio is enabled on a loop point, it provides a method for an
operator to enter a number between 0.1 and 10. To incorporate the
operator entered number into the control strategy it is necessary to use
FST instructions. Refer to Figure 5Ć1 for an example of a ratio
application.
PRIMARY VARIABLE
FT-1
0-50 GPM
PV
A
SP
PI
D
FIC-1
FV 1
A
RTOLD ('FIC-2')
FT-2
0-70 GPM
RSP
PV
AUTO
ATA
FV-2
FIC-2
RATIO CONTROLLER
RATIO CONTROLLER
PID
T
PVLD
('FIC-1')
Figure 5Ć1. Ratio Control
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