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SC100/200 Series Function Block Application Manual EM-6460-C
4.3.11 SAMPLING CONTROL
Sampling control is used to deal with intermittent PV signals by using integral action and output hold function. It is typically
applied to analyzers using gas chromatography or to processes with a large dead time.
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LOOP CONFIGURATION EXAMPLE: END POINT CONTROL WITH A GAS CHROMATOGRAPH
Integral term is applied for ‘
t
1
’ seconds when the synchronization signal is turned on, and then the MV signal is held. Since
the hold function is cancelled after a new PV is given and stabilized, bumpless output tracking cancels changes in the pro-
portional term.
MV output volume by every sampling is determined by the combination of proportional band and integral time.
■
BLOCK DIAGRAM
process
PV
XIC
MV
gas B
gas A
synchronization
signal
t
1
t
1
t
1
t
1
t
1
t
1
PV
SP
MV
gas chromatograph
synchronization signal
time
time
time
Timing Chart
PV
SP
analyzer
(gas chromatograph)
PV
XIC
G02
hold signal
MV
DI
SEQ
G81
TMR
G30
Timer (
t
1
setting)
Sequence
ISW
Internal SW
G31
synchronization signal
analyzer
(gas chromatograph)
