Section 3 Basic Operations
3-8
Basic
Operations
3.6
Using ON/OFF Control
In ON/OFF control, the control output turns OFF when the temperature being controlled reaches the
preset set point. When the manipulated variable turns OFF, the temperature begins to fall and the
control turns ON again. This operation is repeated over a certain temperature range. At this time, the
amount that the temperature must fall before control turns ON again is determined by the “hysteresis”
parameter. Also, what direction the manipulated variable must be adjusted in response to an increase
or decrease in the process value is determined by the “direct/reverse operation” parameter.
■ ON/OFF
Control
• Switching between 2-PID control and ON/OFF control is performed
using the control mode switch 1. When this parameter is set to ON,
2-PID control is selected, and when it is set to OFF, ON/OFF control
is selected. The default is OFF (ON/OFF control).
● Hysteresis
• With ON/OFF control, hysteresis is used to stabilize operation when
switching between ON and OFF. The hysteresis width is referred to
as “hysteresis.”
• Set the hysteresis in the “hysteresis” parameter in the initial setting
level (1).
OFF
ON
Set point
Hysteresis
(heating)
PV
Reverse operation
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