EOS ProControl 2 plus Series User Manual page 7

Active State Central to the use of control on the Series
input on the ProControl receives certain signals from a sensor which constitute
" normal# operation and other signals which constitute an exception to normal
operation.
A digital input can monitor only two states, ON or OFF (alternatively, CLOSED or
OPEN). The Active State would be the state in which the controller would respond
to the digital input, and perform certain actions or generate an alarm. For example,
if a high level float switch in a tank is tripped (turned ON) by rising fluid level, we
can say that its Active State correlates to a situation in which the fluid level is high.
The active state of the float switch could cause the Series
turn off a pump, or initiate some other action. The Series
either ON or OFF is the active state.
An analog input sensor can take on many states (or values) between the minimum
and maximum of its measurement range. The ProControl operator, however, can
set two threshold values which divide the total input span into two functional
regions. These threshold values are more commonly called the Low Alarm Limit
and the High Alarm Limit, although on the Series
somewhat more flexible in use than those names imply. An analog input which has
transcended either its Low Alarm Limit or High Alarm Limit is said to be in its
active state.
10 psi
6
4
0 psi
EAS WAS
Figure 1. Active State
If the ProControl has Alarms Set, when any input enters its active state, a local
beeper will sound on the ProControl. The word Alarm here applies only to the
sounding of a local beeper and is not associated with any process control. The
active state condition is indicated on the LCD display and can be acknowledged by
the operator. The beeper is silenced when it has been acknowledged or after 30
seconds have elapsed. The beeper only operates when the system is operating in
Manual mode.
For instance, consider an analog input sensor which measures
pressure from 0 to 10 PSI. The system operator could set the low
limit to 4 PSI and the high limit to 6 PSI. In this case the Active
High
State would usually be considered as the input state greater than 6
PSI or less than 4 PSI. This interpretation is called Endpoint Active
State (EAS) on the Series
Low
are the areas which need to trigger action or generate alarms. The
opposite interpretation (though rarely used) is also possible and is
called Window Active State (WAS). Any input values between 4 PSI
and 6 PSI would trigger action or generate alarms.
ProControl User's Manual v2.2X
plus
2
is the concept of Active State. Each
plus
2
because the endpoints of the range
4
plus
2
to trigger an alarm,
plus
2
can be set up so that
plus
2
these thresholds are
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