Emerson E2 User Manual

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 
of the Occupancy input. If you wish to follow a schedule 
for occupancy, this input must be tied to the output of a 
Time Schedule application.

The Setpoint Float cell provides users to raise and 

lower the control setpoint based on the value of a sensor 
(called the “float” sensor). The float sensor can be any 
type of analog sensor, but is typically a temperature sen-
sor, since most of the applications for floating setpoints 
involve HVAC and floating the setpoint based on outdoor 
air temperature.

To set up the Setpoint Float cell, you must provide 

three values: a High Float Value, a Low Float Value, and 
an Output Range.

The Output Range is the maximum amount that the 

PID Setpoint may vary. An Output Range of 4, for exam-
ple, means that the control setpoint may only be increased 
by a maximum of 2 and decreased by a maximum of 2. 

The High Float Value and Low Float Value form a 

range of values that determine what portion of the Output 
Range is applied to the final control setpoint. For example, 
suppose a Setpoint Float cell is given a High Float Value 
of 100, a Low Float Value of 0, and an Output Range of 4. 
When the float sensor value is at the high float value, the 
setpoint will be increased by its maximum amount (2). 
When the float sensor value is at the low float value, the 
setpoint will be decreased by its minimum amount (2). For 
all float sensor values in between the High Float and Low 
Float values, the amount added or subtracted to the control 
setpoint will vary linearly.

If floating setpoint control is not desired, this cell can 

be effectively disabled by setting the value of the Float 
Output Range to 0.

The PID Control cell uses a PID algorithm to compare 

the control input value with the control setpoint value. The 
result of this comparison is a percentage from 0-100%. 
The PID Control cell repeats this sequence ever few sec-
onds, and the result is a PID percentage that adjusts over 
time to provide the optimum amount of output to achieve 
the setpoint.

The 0-100% output from the PID Control cell is passed 

along to the Filter cell. 

For users who simply wish to convert an analog output 

to a pulse width modulation or sequenced (staged) output, 
a Loop/Sequence Control application can be programmed 
to bypass PID Control altogether. If this option is selected, 
the Loop/Sequence Control application completely 
ignores the Select, Setpoint Float, and PID Control cells, 
and passes on the value of the control input directly to the 
Filter cell. 

Note that when bypassing PID, the control input must 

be an analog percentage from another E2 application or a 
0-10VDC analog signal from an input point.

The Filter cell’s primary function is to slow the rate of 

change of the PID cell’s output. The filter reads the differ-
ence between the current output value and the value x sec-
onds ago, where x = a user-specified period of time. The 
difference between these two values is multiplied by the 
filter ratio, which is a percentage between 0% and 100%. 
The result of this multiplication is the output value. Note 
that if the filter ratio is at 100%, or if the Filter cell is dis-
abled, the input is not modified by the Filter cell.

The Override cell’s function is to provide a method of 

overriding the analog output going to the Sequencer and 
PWM cells to a user-specified value instead of the value 
called for by the Filter cell. The Override cell can override 
the output to any value between 0% and 100%, and may 
be either fixed or timed. A fixed override remains overrid-
den until the user deactivates the override, while a timed 
override remains in effect until a user-specified time has 
elapsed.

The Loop/Sequence Control application has three con-

trol outputs: a standard 0-100% analog output, a set of up 
to eight staged outputs, and a pulse width modulation 
(PWM) output. The analog control output comes directly 
from the Override cell. However, the same control output 
is fed into the Sequencer and PWM cells for translation 
into digital staged outputs and pulse width modulation.

The Sequencer cell simply activates a certain percent-

age of the Digital State 1-8 outputs based on the percent-
age of the control output. For example, if the control 
output is 50%, the Sequencer cell will activate 50% of the 
total number of stages. The Sequencer cell will always 
round DOWN; that is, if there are four stages in a 
Sequencer cell and the output is 74%, the Sequencer cell 
will only activate two stages (or 50% of the stages). When 
the output climbs above 75%, the third stage will activate.