Executing On/Off Control; On/Off Control - Omron E5CN User Manual

Executing ON/OFF Control

3-7

Executing ON/OFF Control

3-7-1

ON/OFF Control

Hysteresis
3-position control
Parameters
26
In "ON/OFF" control, the control output turns OFF when the currently con-
trolled temperature reaches a preset set point. When the manipulated variable
turns OFF, the temperature begins to fall and the control turns ON again. This
operation is repeated at a certain point. At this time, how much the tempera-
ture must fall before control turns ON again is determined by the "hysteresis
(OUT1)" parameter. Also, how much the manipulated variable must be
adjusted in response in the increase or decrease in the process value is
determined by "direct/reverse operation" parameter.
• Switching between 2-PID control and ON/OFF control is carried out by the
"PID / ON/OFF" parameter (initial setting level). When this parameter is
set to "pid", 2-PID control is selected, and when set to "onof", ON/OFF
control, is selected. Default is "onof".
• In ON/OFF control the hysteresis is used as a differential for switching the
output ON when the temperature moves away from the required set point,
and is used give stability around the set point.
The control output (OUT1) and control output (OUT2) functions are set in
the hysteresis (OUT1) and hysteresis (OUT2) functions respectively.
In standard heating or cooling control, the hysteresis can only be set on
the side approaching the set point.
Revers operation
• In heating and cooling control, a dead band (an area where both control
outputs are "0") can be set to either the heating or cooling side. So, 3-
position control is made possible.
Revers operation
Hysteresis (OUT1)
Symbol
?4/
Standard/heating and cooling: Initial setting level
/:@8
PID / ON/OFF: Initial setting level
;>1B
Direct/reverse operation: Initial setting level
/0.
Dead band: Adjustment level
/?/
Cooling coefficient: Adjustment level
4E?
Hysteresis (OUT1): Adjustment level
/4E?
Hysteresis (OUT2): Adjustment level
ON
OFF
Set point
ON
Heating
side
OFF
Set point
Parameter Name: Level
Section 3-7
Hysteresis (OUT1)
PV
Dead band
Hysteresis (OUT2)
Cooling
side
PV
Description
For specifying control method
For specifying control method
For specifying control method
Heating and cooling control
Heating and cooling control
ON/OFF control
ON/OFF control