Micromod Micro-DCI: 53SL6000 Single Loop Controller - Manual (Page 88)

This section provides information to implement
eight commonly used control strategies:
•
Single Loop Control with Remote Setpoint.
•
Analog Back-up Control.
•
Ratio Control.
•
Auto/Manual Selector.
•
Single Station Cascade Control.
•
Single Station Override Control.
•
Dual Indicator with Re-Transmitted PV.
•
Proportional Speed Floating Control
Information for each strategy is presented in the
same order. There is a brief overview of the control
strategy operation with a process illustration and
an illustration of the signal connector pin assign-
ments, which is followed by descriptive sections of
the connector signals. The applicable parameters
that may require configuring are also included in
these sections.
Many signal paths can be altered in the controller.
To simplify the presentation, it is assumed the path
configuration selections are left at the factory set-
tings unless specified otherwise in the example.
Also provided, is a description of time proportional
output, which can be applied to any of the control
strategies presented in this section.
8.1 Single Loop Control with
Remote Setpoint
Single loop control with remote setpoint is the con-
troller standard factory set functionality (controller
default settings and the SnGL control scheme).
A single loop control strategy with remote setpoint
is illustrated in Figure 8-1. In single loop control, a
continuous output is calculated from the difference
between the process variable (AI1) feedback signal
sent from a field transmitter (e.g., flow meter) and
a setpoint (SP) value. The output is calculated with
the controller PID algorithm, which has propor-
tional, integral, and derivative terms. The effect
these terms have on the output calculation de-
pends on the PID configuration selections (Pb, tr,
and td). As the output (AO1) is determined, it is
applied to a final control element (e.g., valve) to
restore the process to the setpoint value.
The output can also be set manually at the control-
ler, whereby the PID algorithm calculation is not
used. The setpoint can be set locally at the control-
ler or it can originate from a remote source (AI2). If
the alarm limits are configured, the controller will
activate an annunciator whenever the PV exceeds
the configured tolerable limits of change.
Figure 8-1. Single Loop Application
The signal connector is illustrated in Figure 8-2 and
the connector pin assignment descriptions are
provied in the sections that follow. These sections
also contain the applicable display prompts that
may require configuration changes.
Figure 8-2. Single Loop Signals
8.0 Eight Control Strategies
Section 8. Eight Control Strategies 53SL6000 Instruction Manual
8-1