Omega Engineering CN9400 - Manual (Page 27)

Advanced Settings
Before embarking on the Advanced Settings, please
familiarise yourself with the basic operation of the controller
as described in this manual. The following instructions
assume that the user understands how to make the initial
configuration, can navigate through the Function Menu and
successfully Autotune the controller in heating mode.
HEAT COOL STRATEGY CONFIGURATION
Using Cool option
Heat-Cool strategy is a feature that improves control of processes
that need heating and cooling, depending on the conditions, for
example:
Environmental test chambers used in rooms where the
ambient temperature swings above and below the test
temperature.
Plastics extruders where the material initially needs
heating, then cooling, when it begins to heat itself
exothermically due to pressure and friction applied by the
process.
The purpose of cool strategy is to maintain smooth control
of the process during transition from heating to cooling.
This is achieved by using PID control for heating and cooling with the
proportioning bands linked by an adjustable deadband.
From cold (normal procedure on a new installation)
Enter setpoint and allow the process to reach the setpoint using
factory settings for heating only.
Autotune at setpoint
Make the following pre-settings:
Level 1 set to 1.0 to 10 and to 10
Level 2 set to Cool
Level 1 set to At.SP
Autotune will cause a temporary disturbance. Check that the
temperature has stabilised in heating mode before running the
process in cooling mode.
If regular temperature oscillations occur, change CYC.t to optimum
value. See page 9. To select Autotune Calculated Cycle-time
Further adjustments – Cooling
Autotune uses the same calculated bAnd value for both SP1
(heating) and SP2 (cooling). In some processes, regular temperature
oscillations occur when cooling.
Make the following manual adjustment:
In level 1 double the value of
ADVANCED SETTINGS
23
SP2.A
DAC
SP2.A
TUNE
CYC.T CYC.2
BND.2