50
•The Integral Time parameter
(TI)
follows the
PB
parameter. Its range is 1 to 10.000% and
changes to this parameter are inhibited during Adaptive Tune.
•The Derivative Time parameter
(DT)
follows the
TI
parameter. Its range is 0.0 to 99.9 seconds
and changes to this parameter are inhibited during Adaptive Tune. Above 99.9 seconds the
display blanks and integral action is excluded.
After the above values are calculated the controller will switch the
SMART
function to
OFF
. At this
point the Automatic Selection of Integral Pre-Load Value
(AT.IP)
will be available. Actually it is
available always, but will be unreliable (random) until after a SMART trial.
NOTE: It is advisable to avoid changing this value and let the Auto Tuning function select the value.
After a SMART trial, setting
AT.IP
to
Auto
will cause the controller to calculate the integral pre-load
value using the previously determined set point and process gain variables. (If they have not been
pre-determined random numbers may be assigned, and the integral pre-load value determined will
be useless.) When this parameter is set to
Auto
, the value may be read, but not changed by the front
push-buttons.
Setting this parameter to Manual
(nAn)
causes the controller to reload the former keyboard selected
integral pre-load value.
If the operator wishes to skip this step and manually enter a value for Integral Pre-Load, he may do
so by pressing the FUNC key until
nonE
and
GROUP
appears. Press the ▲ key until
2
shows in the
upper display. Press the FUNC key until the lower display shows
IP
. The upper display shows the
Integral Pre-Load default value of 50.0% or the previously selected value. The operator can change
this value from a range of 0.0% to 100.0%, except that the value cannot be changed if the
automatic Selection of Integral Pre-Load
(AT.IP)
has been set to
AUTO
.
Although the Filter Time Constant
(AT.FL)
is preset at 1 second, the Automatic Selection of Filter
Time Constant
(AT.AFL)
can be engaged to find the most appropriate filter for the process.
Setting this to Auto will cause the SMART (TUNE) function to search fopr the best filter time constant
before applying a power change. During this process, the
SMRT
LED will flash at a fast rate. The
default value for
(AT.AFL)
is manual mode
(nAn)
.
7.3.4 ENGAGING THE ADAPTIVE TUNING ALGORITHM
(ATC770 IN AUTOMATIC MODE)
The Adaptive Tuning Algorithm is an on-line algorithm that “observes” the measured value and looks
for oscillation due to a variation of the load or the set point. When a significant pattern is
“recognized,” the decision procedure starts to recalculate the PID or PI parameters of the controller.
While the ADAPTIVE procedure is enabled these parameters can only be monitored. To enable this
mode, press the FUNC key until
nonE
and
GROUP
show on the display. Press the ▲ key until
2
shows in the upper display. Press the FUNC key until the upper display shows
OFF
and the lower
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