Setpoint Scheduler; Overview; Table 37 Sps Inputs And Current State - Honeywell 900 User Manual

Overview

A setpoint schedule produces multiple setpoint outputs on a common time base. A setpoint schedule
contains multiple segments. Each segment contains multiple ramp or soak setpoints, multiple auxiliary soak
outputs, and multiple events. The last segment setpoint is always a soak (because there is no subsequent
setpoint to ramp to).
The Setpoint Scheduler can run any of the schedules in controller memory. Any schedule can be edited and
saved in one of the "slots" in the controller's memory.
A Setpoint guarantee function (known as guaranteed hold) is provided that holds the Scheduler if a process
variable exceeds a predefined deviation from setpoint. Guaranteed hold is set on a per-segment basis and
can be set for high deviation, low deviation, high and low deviation, or none.
The schedule may be changed (with some exceptions) from the current state to a new state by the operator
as well as by inputs to the Scheduler function block in the controller configuration. Table 37 lists the
resulting states.
Input
RESET
HOLD
RUN
GHOLD
With regard to changing schedule state, if more than one function block input is on in the same execution
cycle, RESET has priority over HOLD and RUN, and GHOLD has priority over RUN.
Also, function block inputs will override inputs from the Control Station, which occur during the same
execution cycle. Finally, state changes from the Control Station are processed on the basis of the "last
change wins."
Revision 9
May 2014

Setpoint Scheduler

Table 37 SPS inputs and current state

READY HOLD RUN
READY READY RUN
HOLD HOLD HOLD
RUN RUN RUN
READY HOLD GHOLD
900 Control Station User Guide
Current State
GHOLD STOP
READY READY
HOLD STOP
GHOLD STOP
GHOLD STOP
DISABLE
READY
HOLD
RUN
READY
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