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Setting Control Specifications Section 4-3
4-3-2 Selecting the Control Method
The control method can be set to either 2-PID control or ON/OFF control.
Note This parameter can be set only when operation is stopped.
ON/OFF Control In ON/OFF control, the control output turns OFF when the currently controlled
temperature reaches a preset set point. When the manipulated variable turns
OFF, the temperature begins to fall and the control output is turned ON again.
This operation is repeated at a certain level. The Hysteresis (Heating) param-
eter determines how much the temperature must fall before the control output
is turned ON again. Also, the Direct/Reverse Operation parameter determines
whether the manipulated variable is increased or decreased in response to an
increase or decrease in the process value.
■ Hysteresis
ON/OFF control incorporates a hysteresis setting to stabilize operation when
switching ON and OFF. The width of the hysteresis loop determines the sensi-
tivity.
• The control output (heating) and control output (cooling) hysteresis set-
tings are made with the Hysteresis (Heating) and Hysteresis (Cooling)
parameters, respectively.
• The sensitivity of standard control (heating or cooling) is set with the Hys-
teresis (Heating) parameter, regardless of the setting of the Direct/
Reverse Operation parameter.
• The Hysteresis (Cooling) parameter is effective only when using heating/
cooling control.
Note 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 (****) decimal point position
setting will be treated as setting 1 (***.*).
Variable type Parameter name Setting range Default
E5/A5 PID/OnOff (Channel) 0: 2-PID control
1: ON/OFF control
0
Conditions for use No special conditions
Variable type Parameter name Setting range Default
D5/95 Hysteresis (Heating) (Channel) 1 to 9999 EU 10
Hysteresis (Cooling) (Channel) 1 to 9999 EU 10
Conditions for use The control method must be set to ON/OFF control.
Hysteresis (Heating)
Set point
OFF
ON
PV
Heating control
Hysteresis (Cooling)
Set point
OFF
ON
PV
Cooling control
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