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The display indicates the level of security of the parameter, it is now possible to change this level by pressing the
Press
for more than 4 s to record the new state.
Example : If ASP1 , rAmP are configured in level 0, and PB , ti , td , ASP2 are configured in level 1 and the other parameters in level
3, the configuration menu will be as follows :
3.7. AUTOTUNE PROCEDURE
Ensure that all the parameters are correctly configured. Ensure that Pb is not at 0, because autotune is not possible in ON-OFF
mode.
!
The temperature may oscillate more or less strongly around the setpoint during the autotune. If these overshoots
are likely to harm the installation, perform the autotune with a slightly lower setpoint value.
Adjust the setpoint, then simultaneously press the
the autotune programme is running.
SV
During the autotune, the controller searches for the P-I-D parameters best suited for the process. The results are then automatically
saved in a non-volatile memory.
To stop the autotune, press
no longer possible to stop the procedure. The display continues to flash.
!
Depending on the process conditions, the autotune may last a long time (more than an hour). Be patient!
3.8. MANUAL ADJUSTMENT OF P-I-D
Ensure that all the parameters are correctly set.
Introduce a nil proportional band Pb and a nil hysteresis hYSt , then set the setpoint
value. In these conditions, the temperature oscillates around the setpoint
Observe and note the reaction of the process:
- peak-peak amplitude (P) of the first oscillation, in degrees
- period of oscillations (T) in seconds
The approximative adjustments of the P-I-D can then be deduced as shown on the right.
Introduce these values and observe the response of the system. If necessary, adjust Pb, ti and td in accordance with the table below.
Parameter
Pb : proportional band
ti : integral time
td : derivative time
rAmP
SV
ASP1
Learning period
ON/OFF operation
setpoint
and
simultaneously; the display stops flashing. But if the controller is in the checking phase, it is
Symptom
Slow response
High overshoot or oscillation
Slow response
Instability or oscillation
Slow response or oscillation
High overshoot
Long
Pb
ti
and
keys for more than 4 seconds. The display starts to flash, showing that
Checking period
P-I-D operation
Pb, ti, td
obtained
33
ASP2
td
P.I.D
+
Fuzzy logic
End of
Control
autotune
PV
P
Solution
Decrease Pb
Increase Pb
Decrease ti
Increase ti
Decrease td
Increase td
and
keys.
Pb = P (°C or °F)
ti = T (seconds)
td = T/4 (seconds)
SV
T
Time
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