Instruction Manual

Installation and Operation Handbook Tuning
2416 Controller 4-1
4 Chapter 4 TUNING
Before tuning please read Chapter 2, Operation, to learn how to select and change a
parameter.
This chapter has five main topics:
WHAT IS TUNING?
AUTOMATIC TUNING
MANUAL TUNING
COMMISSIONING OF MOTORISED VALVE CONTROLLERS
GAIN SCHEDULING
4.1 WHAT IS TUNING?
In tuning, you match the characteristics of the controller to that of the process being
controlled in order to obtain good control. Good control means:
Stable ‘straight-line’ control of the temperature at setpoint without fluctuation
No overshoot, or undershoot, of the temperature setpoint
Quick response to deviations from the setpoint caused by external disturbances, thereby
restoring the temperature rapidly to the setpoint value.
Tuning involves calculating and setting the value of the parameters listed in Table 4-1. These
parameters appear in the Pid list.
Parameter
Code
Meaning or Function
Proportional
band
Pb
The bandwidth, in display units, over which the output power is
proportioned between minimum and maximum.
Integral time
ti
Determines the time taken by the controller to remove steady-
state error signals.
Derivative
time
td
Determines how strongly the controller will react to the rate-of-
change of the measured value.
High Cutback
Hcb
The number of display units, above setpoint, at which the
controller will increase the output power, in order to prevent
undershoot on cool down.
Low cutback
Lcb
The number of display units, below setpoint, at which the
controller will cutback the output power, in order to prevent
overshoot on heat up.
Relative cool
gain
rEL
Only present if cooling has been configured and a module is
fitted. Sets the cooling proportional band, which equals the Pb
value divided by the rEL value.
Table 4-1 Tuning parameters