247
hunting
will be reduced if the integral time is increased or the proportional band
is enlarged.
Control by measured PID
(when loose hunting occurs)
Enlarge I or P.
SV
•
If the period is short and hunting occurs, it may be
that the control system re
-
sponse
is quick and the derivative operation is too strong. In that case, set the
derivative operation lower.
Control by measured PID
(when hunting occurs in a short period)
Lower D.
SV
Flags ER:
Content of
:
DM word is not BCD, or the DM area boundary has been
exceeded.
A PID parameter SV is out of range.
The
PID operation was executed but the cycle time was two times
the
sampling
period. PID(––) will be executed for
this error only even when
ER (SR25503) is ON.
CY: The PID operation is being executed.
Example This example shows a PID control program using PID(––).
Amplifier (See note below.)
Fan (Output word IR 111)
Heater (Output word IR110)
Temperature sensing element
(Output word IR 100)
Amplifier (See note below.)
#0 #1
AD001 DA001
C200HS
CPU
Note Motors
and
heaters cannot be directly connected from a Analog Output Unit. An
amplifier (i.e., a current amplification circuit) is required.
Special Math Instructions Section 5-21
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