Auto-Tuning - gefran 600 Manual De Uso

The function works for single output systems (heating or cooling).
The self-tuning action calculates optimum control parameter values during process startup.
The variable (for example, temperature) must be that assumed at zero power (room temperature).
The controller supplies maximum power until an intermediate value between starting value and setpoint is reached, after which it zeros power.
PID parameters are calculated by measuring overshoot and the time needed to reach peak. When calculations are finished, the system
disables automatically and the control proceeds until the setpoint is reached.
How to activate self-tuning:
A. Activation at power-on
1. Set the setpoint to the required value
2. Enable selftuning by setting the Stun parameter to 2 (CFG menu)
3. Turn off the instrument
4. Make sure the temperature is near room temperature
5. Turn on the instrument again
B. Activation from keyboard
1. Make sure that key M/A is enabled for Start/Stop selftuning
(code but = 6 Hrd menu)
2. Bring the temperature near room temperature
3. Set the setpoint to the required value
4. Press key M/A to activate selftuning (Attention: selftuning interrupts if the key is pressed again)
The procedure runs automatically until finished, when the new PID parameters are stored: proportional band, integral and derivative times
calculated for the active action (heating or cooling). In case of double action (heating or cooling), parameters for the opposite action are
calculated by maintaining the initial ratio between parameters (ex.: CPb = HPb * K; where K = CPb / HPb when self-tuning starts). When
finished, the Stun code is automatically cancelled.
Notes:
- The procedure interrupts when the setpoint value is exceeded. In this case, the Stun code is not cancelled.
- _ It is advisable to enable one of the configurable LEDs to signal selftuning status. By setting one of parameters LED1, LED2, LED3 = 4 or 20
on the HRd menu, the respective LED will be on or flashing when selftuning is active.
N.B.: Action not considered in ON/OFF control
Enabling the auto-tuning function blocks the PID parameter settings.
Auto-tuning continues to measure the oscillations of a system, finding as quickly as possible the PID parameter values that reduce the current
oscillation. It does not act if the oscillations drop to values below 1.0% of the proportional band.
It is interrupted in case of variation of the set-point, and automatically resumes with constant set-point.
The calculated parameters are not saved. When the instrument is turned off, the controller resumes with the parameters programmed before
auto-tuning was enabled.
If you switch to Manual, Auto-tuning ends the procedure.
c_Pb
SP+cSP
SP
h_Pb
+100%
Control output
0%
-100%
Control output with proportional action only if proportional heating band
overlaps proportional cooling band.
PV = Process Value
SP+cSP = cooling setpoint
c_Pb = Proportional cooling band
In this control mode (enabled with Ctr = 14 parameter) the type of cooling has to be specified.
Cooling PID parameters are therefore calculated based on heating parameters according to the specified ratio.
(for example: C.ME = 1 (oil), H_Pb = 10, H_dt = 1, H_It = 4 implies: C_Pb = 12,5, C_dt = 1, C_It = 4)
We advise you to apply the following values when setting output cycle times:
Air T Cool Cycle = 10 sec.
Oil T Cool Cycle = 4 sec.
Water T Cool Cycle = 2 sec.
NB.: Cooling parameters cannot be modified in this mode.
12 • SELF-TUNING
13 • AUTO-TUNING
14 • CONTROLS
PV
time
Heating/Cooling control with relative gain
Process
Variable
S.P.
S.P. - t.a.
2
t.a.
SP
SP+cSP
+100%
Control output
0%
-100%
Control output with proportional action only if proportional heating band
overlaps proportional cooling band.
SP = Heating Setpoint
h_Pb = proportional heating band
31
Peak
T
PV
c_Pb
h_Pb
time
Time