22
ON/OFF CONTROL
The controller operates in On/Off Control when the
Proportional Band is set to 0.0%. In this control mode, the
process will constantly oscillate around the setpoint value. The
On/Off Control Hysteresis (balanced around the setpoint) can be
used to eliminate output chatter. Output O1 Control Action can
be set to reverse for heating (output on when below the setpoint)
or direct for cooling (output on when above the setpoint)
applications.
ON/OFF CONTROL -
REVERSE OR DIRECT ACTING FIGURES
Note: CHYS in the On/Off Control Figures refers to the On/Off
Control Hysteresis (
4*?)) in parameter Module 2.
For heat and cool systems, O1 Control Action is set to reverse
(heat) and the Alarm 2 Action is set to cooling (O2). The
Proportional Band is set to 0.0 and the Relative Gain in Cooling
to 0.0. The Deadband in Cooling sets the amount of operational
deadband or overlap between the outputs. The setpoint and the
On/Off Control Hysteresis applies to both O1 and O2 outputs.
The hysteresis is balanced in relationship to the setpoint and
deadband value.
CONTROL MODE EXPLANATIONS
ON/OFF CONTROL - HEAT/COOL OUTPUT FIGURES
PID CONTROL
In PID Control, the controller processes the input and then
calculates a control output power value by use of a modified
Proportional Band, Integral Time, and Derivative Time control
algorithm. The system is controlled with the new output power
value to keep the process at the setpoint. The Control Action for
PID Control can be set to reverse for heating (output on when
below the setpoint) or direct for cooling (output on when above
the setpoint) applications. For heat and cool systems, the heat
(O1) and cool (O2) outputs are both used. The PID parameters
can be established by using Auto-Tune, or they can be Manually
tuned to the process.
TYPICAL PID RESPONSE CURVE
To Next Page
Loading...
Need help?
General
