Emerson E2 Manuel D’Utilisation

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.

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.

An abstract diagram of the control and output cells is 

shown in Figure 11-24.

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AV

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