The Single Setpoint Mode uses up to four configurable limits to report an alarm. This method also sets the Alarm State attribute of the object to which it is added. You can configure Single Setpoint Mode using either a mapped setpoint reference or a fixed number set in the warning reference. For example, you can configure the Analog Alarm extension to issue an alarm if the temperature in a room falls below 15.6˚C (60˚F).
The Analog Alarm Object determines its new alarm state based upon receipt of a change. The new alarm state is based on the following:
Newly reported value and reliability
Current alarm state (present value)
- Defined alarm and warning limits. Once you set the High and Low Alarm Limits, the High Warning Limit is calculated by adding the High Warning Offset to the Cooling Setpoint Reference Value. The Low Warning Limit is calculated by subtracting the Low Warning Offset from the Heating Setpoint Reference Value.
Value reported by the Setpoint Reference (if defined) written to Warning Reference Value
Delay Timer Active
Reference Delay Timer Active
Figure 1 shows the Present Value of the Analog Alarm as it changes.
The Delay Time period begins when the Warning Reference changes. The Input Value is not calculated during this time. The Input is normal at the end of the Reference Delay Time, so the Present Value stays normal.
The Report Delay period begins when the Present Value transitions to any state from the Normal state, or the value of the Command Reference changes. Transitions to and from states other than Normal are reported immediately.