Output Cells; Diagram; Loop/Sequence Control Cell Descriptions; The Select Cell - Emerson E2 Installation And Operation Manual

change drastically. The filtered PID percentage is sent to
the final control cell, the Override cell.
Step 5: Override - Once the PID percentage is figured,
the Override cell provides for overrides of the PID per-
centage. The Override cell, when activated by a user-initi-
ated manual override, will block the PID percentage from
being sent to the outputs, replacing it with a fixed value
specified by the user.
The value from the Override cells is then sent to the
Loop/Sequence Control's PID output, and also to the two
output cells for conversion to stages and PWM.

11.13.1.2 Output Cells

The two output cells make no alteration of the PID per-
centage determined by the control cells, but re-interpret
them in a way that can be used for systems with multiple
SELECT CELL
Occ SP
In 1
AV
Unoc SP
In 2
AV
Occupied
Occup
DV
SETPT FLOAT
AV
SP In
Float
Float
AV
PID CONTROL
AV
Setpoint
Control Value
Input
AV
AV
Figure 11-24
- Loop/Sequence Control Application Diagram
11.13.2 Loop/Sequence Control Cell
Descriptions

11.13.2.1 The Select Cell

The Select cell's function is to provide the control set-
point to the PID Control cell, and to switch between occu-
pied and unoccupied setpoints based on the current state of
Loop/Sequence Control
FILTER
In
AV
SP Out
PID Out
AV
AV = Analog Value
DV
stages and/or with pulse width modulation.
Sequencer - The Sequencer cell will use the percent-
age to activate an equivalent percentage of its defined
stage outputs. The Sequencer supports up to eight cells,
and also provides for minimum on/off times and first-on/
last-off sequencing.
PWM - The PWM cell drives a digital output whose
ON time per pulse width modulation period is equal to the
PID percentage. In other words, if the PWM cell is set
with a pulse width of 10 seconds, a PID percentage of 60%
turns the output ON for 6 seconds, OFF for 4 seconds, ON
for 6 seconds, etc.

11.13.1.3 Diagram

An abstract diagram of the control and output cells is
shown in Figure 11-24.
OVERRIDE
In
AV
Out
AV
SEQUENCER
Stage 1
Input Stage 2
Stage 3
Stage 4
Stage 5
Stage 6
Stage 7
Stage 8
PWM
AV
In Out
DV = Digital Value
occupancy.
To determine whether to use the occupied setpoint or
the unoccupied setpoint, the Select cell reads a digital
input. If this input is ON (OCC), the occupied setpoint is
used. If this input is OFF (UNO), the unoccupied setpoint
is used.
If the occupancy input is NONE, the Select cell will
Analog PID/PWM
Loop Output
Out
AV
Digital Stage
1-8 Output
DV
DV
DV
DV
DV
DV
DV
DV
Digital PWM
Output
DV
•
Software Overview
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