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94 UDC 3300 Process Controller Product Manual 4/00
Lower Display
Prompt
Upper Display
Range of Setting
or Selection
Parameter
Definition
CONT ALG
(continued)
3PSTEP THREE POSITION STEP—The Three Position Step
Control algorithm allows the control of a valve (or other
actuator) with an electric motor driven by two controller
relay outputs; one to move the motor upscale, the other
downscale without a feedback slidewire linked to the
motor shaft. The deadband is adjustable in the same
manner as the duplex output algorithm.
The Three Position Step Control algorithm provides an
output display (OUT) which is an estimated motor position,
since the motor is not using any slidewire feedback.
Although this output indication is only an approximation, it
is “corrected” each time the controller drives the motor to
one of its stops (0 % or 100 %). It avoids all the control
problems associated with the feedback slidewire (wear,
dirt, noise). When operating in this algorithm, the
estimated OUT display is shown to the nearest percent
(i.e., no decimal).
Refer to the Operation section for motor position displays.
As a customer configurable option, when a second input
board is installed, the motor slidewire can be connected to
the controller. The actual slidewire position is then shown
on the lower display as POS. This value is used for
display only. It is NOT used in the Three Position Step
algorithm. To configure this option, set Input 2 actuation
to SLIDEW. Calibrate the slidewire.
Other prompts affected: DEADBAND
PIDLOOPS*
*Only available on
Expanded Model
DC330E Dual loop.
1 LOOP
2LOOPS*
CASCAD*
PID LOOPS—This is the PID loop selection.
1 LOOP—Select to use one loop of control.
2 LOOPS—Select to use two PID loops of control, each
with two sets of tuning parameters and a set of control
parameters.
CASCADE—Select for Cascade Control. In a cascade
control system the output of one PID loop is used to adjust
the setpoint of the second control loop and the second
loop’s output actually adjusts the final control element.
ATTENTION
To enable a cascade loop, hold in the
SETPOINT SELECT key until the RSP Annunciator
lights and an “I” appears as the upper display’s leftmost
character to indicate Cascade mode. Pressing the key
again disables the Cascade Loop and the annunciators
turn off.
CONT2ALG
The CONTROL 2 ALGORITHM lets you select the type of
control for Loop 2 that is best for your process. Only
available if the controller is configured for Cascade or
2-Loop control.
3Pstep and On/Off are not available for the second control
loop.