DESCRIPTION AND OPERATION
MODES OF OPERATION
2 - 12
I-E96-117B
®
Ratio Station
A variable controlled by another process variable determines
the set point for a ratio station. The MFP module calculates the
set point by multiplying the wild variable by a ratio index set in
function code 80. The operator can change the ratio index
through the set raise/lower pushbutton. By changing the ratio
index, the operator changes the set point ratio that the control
algorithm uses to calculate the set point. When the SAC station
transfers to manual operation from automatic ratio operation,
it goes into manual basic operation. Figure
shows an
example ratio station.
While in ratio mode, the bar graph indicates the value of the
set point while the alphanumeric indicates the ratio index. The
Figure 2-6. Ratio Station Configuration
WILD VARIABLE
CONTROLLED VARIABLE
(156)
80
(7)
70
(7)
60
S2
S7
S9
S8
S6
S1
S1
S1
S5
S4
S3
S10
APID
BD
CO
BI
SP
FF
N/A
N/A
R
PV
TF
TR
DI
II
(80)
(79)
120
121
122
123
124
125
126
127
128
129
101
100
102
103
104
105
S1
S2
S3
S24
S29
S28
S27
S26
S25
S4
S22
S21
S20
S19
S18
S5
S30
M/A
MFC/P
SP
O
C-F
C
C/R
A
PV
AI1
DI2
DO4
DO3
DO2
DO1
DI3
DI1
AI2
AO2
AO2
AO1
AO1
AI4
AI3
ST
SP
A
HAA
TRS2
AO
LDA
HDA
LAA
TR
CX
LX
C/R
AX
MI
TS
TRPV
CISI/O
T00291A
CONTROLLED VARIABLE
UNCONTROLLED (WILD) VARIABLE
BLEND TANK
FC
FY
FY
FT
FT
0
SP
PV