IM 01C25R03-01E
A-7
APPENDIX 1. SIGNAL CHARACTERIZER (SC) BLOCK
A1.5 Application Example
A1.5.1 Input Compensation
The following is an application example of pH com-
pensation made by performing feedback control.
The pH is a value representing the degree of acidity or
alkalinity and ranges from 0 to 14. pH 7 indicates
neutral, a value smaller than 7 represents acidity, and a
value larger than 7 denotes alkalinity. It is very
difficult to control pH with a quickly changing reaction
rate at a point near 7.
FA0106.EPS
Figure A1.6 pH and Reagent Flow
To control this pH, the input is regulated using line-
segment approximation, gain, and input compensation.
FA0107.EPS
Figure A1.7 Input Compensation
The following shows the approximation-value graph of
GX Output that is approximation-value output and GX
Input that is pH input. pH with a quickly changing
reaction rate can be controlled at a point near neutral 7
according to the following graph.
FA0108.EPS
CURVE_Y
CURVE_X
Figure A1.8 Approximation Curve
A1.5.2 Calorie Flow Compensation
AI_1: Inlet temperature, AI_2: Outlet temperature,
AI_3: Flow rate
SC: Corrects the inlet and outlet temperatures.
AR: Calculates a calorie flow rate on the basis of the
difference between the corrected inlet and outlet
temperatures.
AI1
OUT
SC
OUT_2
OUT_1
IN_1
IN_2
SWAP_2=OFF
AR
IN_1
IN_2
OUT
IN
AI2
OUT
AI3
OUT
FA0109.EPS
Figure A1.9 Calorie Flow Rate Compensation (SWAP_2 = Off)
A1.5.3 Backward Control
SC: The controlled variable output from PID is
converted into an information quantity that can be
interpreted by AO, and backward information from AO
is converted into an information quantity that can be
interpreted by PID before being transmitted to the PID.
AI
OUT
AO
CAS_IN
SC
OUT_2
OUT_1
IN_1
IN_2
PID
BKCAL_IN
OUT
IN
BKCAL_OUT
SWAP_2=ON
FA0110.EPS
Figure A1.10 Backward Control (SWAP_2 = On)
