2 output cells, 3 diagram, 2 loop/sequence control cell descriptions – Emerson E2 User Manual
Page 182: 1 the select cell, 2 output cells -40, 3 diagram -40, 2 loop/sequence control cell descriptions -40, 1 the select cell -40
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E2 RX/BX/CX I&O Manual
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
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.
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
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
assume this application will not use occupancy-based set-
points, and will use the occupied setpoint only (no switch-
ing).
Note the Select cell does not have any on-board sched-
ule function to determine for itself whether the building is
occupied or unoccupied. It relies solely on the digital state
Figure 11-24
- Loop/Sequence Control Application Diagram
SELECT CELL
SETPT FLOAT
PID CONTROL
FILTER
OVERRIDE
SEQUENCER
PWM
Occ SP
Unoc SP
Occupied
In 1
In 2
Occup
SP In
Float
SP Out
Setpoint
Input
PID Out
In
Out
In
Out
Input
In
Out
Stage 1
Stage 2
Stage 3
Stage 4
Stage 5
Stage 6
Stage 7
Stage 8
DV
AV
DV = Digital Value
AV = Analog Value
AV
AV
DV
AV
AV
AV
AV
AV
AV
AV
AV
AV
AV
DV
DV
DV
DV
DV
DV
DV
DV
DV
Float
Control Value
Analog PID/PWM
Loop Output
Digital Stage
1-8 Output
Digital PWM
Output