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SC100/200 Series Function Block Application Manual EM-6460-C
4.3.10 VARIABLE PID CONTROL
Different sets of PID parameters are automatically applied following loop characteristics changes caused by switching sen-
sor’s measuring range
,
control valves or set values (e.g. set values change in accordance with the progress of program steps
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LOOP CONFIGURATION EXAMPLE: TEMPERATURE CONTROL DIVIDED INTO THREE TEMPERATURE ZONES
■
BLOCK DIAGRAM
■
OPERATION
The TIC’s current SP is supplied to the input of G30 High/Low Alarm block. High and low setpoints divide the set value range
in three zones. A Parameter Setter block is applied to each zone.
The high/low setpoints should be provided with a deadband to avoid cycling between parameters.
[Caution of using Parameter Setter block]
Parameters in each function block can be rewritten approx. one hundred thousand (100,000) times (according to nominal
specification of the EEPROM).
For example, if you rewrite a parameter every one hour, the EEPROM is usable approx. eleven years. Please consider this
information carefully when you design an application of this function block.
fuel
TIC
PV
MV
furnace
Setting different PID parameters for
each of three temperature zones
temp
temp
PV
current SP
parameter setting
TIC
G02
MV
PMS
G31
PMS
G32
PMS
G33
PVA
G30
SEQ
Parameter Setter
High/Low Alarm Sequence
G81
Parameters are switched by one-shot command.
setpoint
PID parameters
low limit
A2
high limit
A1
G31
G32
G33