ATC770 Microprocessor-Based Pressure/Process Controller 51
display shows
SMART
. Press the ▼ or ▲ key until the upper display changes to
ON
. Press the FUNC
key to set the value. This will activate the Adaptive Tuner Algorithm, and will maintain the correct
PID or PI parameters for the process. It will remain on until manually turned off. It will also come on
anytime that the ATC770 is in Automatic mode.
As the tuning process progresses, press A/M to return to the operating screen, and observe the
process. The setpoint
(SP)
can be touched up in the automatic mode in the main screen. The
operator may alternately display the Output %, Set Point, Peak Value, or RPM by pressing the up
arrow key.
7.3.5 AUTOMATIC STAND-BY IN THE EVENT OF A PROCESS UPSET
The Automatic Stand-By function avoids overshoot due to temporary process interruptions (i.e. if the
pressure goes to zero). If this happens, the controller output quickly reaches saturation for integral
factor; when the process restarts, the controlled output will have an excessive and dangerous
overshoot, (i.e. it will start at full speed).
When the Automatic Stand-By
(ASB)
function is activated, the algorithm monitors the controller
input and output: when the input value goes lower than a threshold (specified by the Automatic
Stand-By Pressure Low Limit parameter
ASB.PL
). When this happens, and the output value reaches
the saturation condition and the control output saves the last value stored when the process was
stable.
This freezing of the output of the controller will last for the time specified by the Automatic Stand-By
Recovery Time
(ASB.RT)
parameter. If the input does not recover within the specified time, the
output value is forced to zero.
If the controller input recovers within the specified time, the algorithm waits for 2-1/2 times the
integral value; after this time has elapsed, the controller will come back automatically to normal
running condition to the output level calculated when the process was stable.
To set the Automatic Stand-By
(ASB)
, the Automatic Stand-By Pressure Low Limit parameter
(ASB.PL)
, and the Automatic Stand-By Recovery Time
(ASB.RT)
, 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 lower display shows
ASB
. Press the ▼ or ▲ key until the upper display changes to
ON
.
Press the FUNC key to set the value. The lower display will show
ASB.PL
, and the lower display will
show a percentage from 0 to 15% of the full scale value. Press the ▼ or ▲ key until the upper
display changes to the desired value.
Press the FUNC key to set the value. The lower display will show
ASB.RT
, and the lower display will
show
OFF
, or a time from 0 to 60 seconds. Press the ▼ or ▲ key until the upper display changes to
the desired. Press the FUNC key to set the value.
OFF
means that no recovery time is applied, and
the frozen output value is held indefinitely.
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