Omron EJ1

64
Setting Control Specifications Section 4-3
■ Three-position Control
In heating/cooling control, a dead band area can be set where the MV is 0%
for both heating and cooling. with a dead band, 3-position control can be
achieved.
2-PID Control (Two-
degrees-of-freedom
PID)
The proportional band (P), integral time (I), and derivative time (D) must be
set for 2-PID control.
■ PID Settings
When the control characteristics are unknown, perform autotuning (AT). When
AT is executed, the optimum PID constants for the set point at that time are
set automatically.
When the control characteristics are already known, the PID parameters can
be set directly to adjust control. The PID parameters are set with the Propor-
tional Band (P), Integral Time (I), and Derivative Time (D) parameters.
Note Refer to 4-3-8 Tuning for details on autotuning.
Note (1) Refer to 4-7-1 Bank Function for details on banks.
(2) The decimal point position is determined by the sensor selection. With
analog inputs, the decimal point position is determined by the Decimal
Point Position parameter setting. In this case, however, the 0 (****) deci-
mal point position setting will be treated as setting 1 (***.*).
• Proportional action: In proportional action, the MV is proportional to the
deviation (control error).
• Integral action: This control action produces an output that is propor-
tional to the time integral of the control error. An off-
set normally occurs in proportional control, so
proportional action is used in combination with inte-
gral action. As time passes, this offset disappears
and the control temperature (process value) matches
the set point.
OFF
ON
PV
Heating side
Hysteresis (Cooling)
Hysteresis (Heating)
Dead band
Cooling side
Set point
Variable type Parameter name Setting range Default
D0/90 Proportional Band (BANK) 1 to 9999 EU
(See note 1.)
80
Integral Time (BANK) 0 to 3999 Seconds 233
Derivative Time (BANK) 0.0 to 999.9 Seconds 40.0
Conditions for use The control method must be set to 2-PID control.