— 22 —
5-2 Auto-tuning (AT)
The auto-tuning is automatic measurement, computation, and setting of the P.I.D. constant that are performed
by the micro-controller. Prior to the auto-tuning, complete the setting of input range (P-SL, P-SU, P-dP), a set
value (SV), alarm setting (H,L), and proportional time cycle (TC).
How to start the auto-tuning
Set the parameter, AT to either “1” or “2” by using
or
key, and press the
ENT
key to start auto-turning.
Then the point indicator at the lower right will start blinking. When auto-tuning ends, parameter AT is automatically
set to 0 after flashing at decimal point of digit 1 disappears.
w
Low PV type (AT=2) : Overshoot decreases when
tuning is performed.
(a) The P.I.D. parameter calculated by auto-tuning, will be retained even if the power is turned off. If, however,
the power is turned off in the auto-tuning, you must restart the auto-tuning.
(b) The PV may be changed greatly depending on the process, because the control output is ON/OFF action
in the auto-tuning. So, do not use the auto-turning if the process does not allow a significant variation of
PV.
Also, the auto-tuning should not be used in a quick-responsive process such as pressure control and flow
control.
(c) If the auto-tuning fails to complete in four hours, an abnormality in the auto-tuning may be suspected. In
this case, recheck the wiring, control output operations (nomal and reverse action), and parameters such
as the input sensor type.
(d) Carry out the auto-tuning again when the SV is significantly changed, parameter P-SL, P-SU or P-dP is
changed or a controlled equipment operation is changed.
(e) Figures
q
and
w
show the behavior of PV during the auto-tuning.
(f) Perform the auto-tuning also when fuzzy control is selected in the control type setting.
q
Standard type (AT=1)
Setting code (AT)
0
1
2
When auto-tuning
is not performed or
when it is cancelled
Standard type
(auto-tuning on the
basis of SV)
Low PV type (auto-
tuning on the basis
of SV
･
10%FS)
Start of AT
End of AT
AT in operation
Set value (SV)
100%
0%
ON-OFF action
PV
ON
OFF
ON
OFF
(Measured value)
PID control
Start of AT
End of AT
AT in operation
Set value (SV)
100%
0%
ON-OFF action
PV
ON
OFF
ON
OFF
PID control
SV
-
10%FS
(Control output)
(Control output)
(Measured value)
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
