Frozen Alarm Calculations

There are three Frozen alarm calculation types that can be implemented with the CygNet Enhanced Point Scheme. See Understanding the CVS Metadata File for more information about the elements and attributes that define the CygNet Enhanced Point Scheme. For more information, see Alarm Calculation Types.

See the following subsections for details:

• Frozen Percent
• Frozen Value
• Frozen Value with Delay

Frozen Percent

The Frozen (Percent) alarm uses the Frozen Percent (FROZE_PCT) calculation. Whenever the time interval is reached, the system will calculate the percentage change from the newest value older than the time interval and set the alarm bit if the percentage change is less than the threshold.

The following image shows the area of an Analog Alarm Settings page of a PNT Editor with an enabled Frozen (Percent) alarm using the Frozen Percent calculation type:

Alarm Calculation Configuration — Frozen Percent

Calculation Parameters

• Minimum percentage threshold (calcparm1) — minimum required percentage difference over the time interval

• Time Interval in Seconds (calcparm2) — time interval

Equation

Percent Change = fabs((Updated Value/Previous Value) -1) X 100

• If the Percent Change < minimum allowed percentage change, alarm is set.
• If the Percent Change ≥ minimum allowed percentage change, alarm is not set.

Example

• calcparm1 = 10%
• calcparm2 = 10 seconds

In this example, the Frozen (Percent) alarm bit is set because the percentage change (4.167%) is less than the minimum percentage threshold (10%).

• Updated Value = 75
• Previous Value (newest older than time interval) = 72

Percent Change = ((75/72) -1) X 100 = 4.167%

Alarm Calculation Results — Frozen Percent

Frozen Value

The Frozen alarm uses the Frozen Value (FROZE_VAL) calculation. Whenever the time interval is reached, the system sets the alarm bit if the point’s value has not changed in this time period, and clears the alarm every time a point is updated with a different value. The time interval is relative to the time that the CVS received the point value, not relative to the time of the point value’s timestamp.

The following image shows the area of an Analog Alarm Settings page of a PNT Editor with an enabled Frozen alarm using the Frozen Value calculation type:

Alarm Calculation Configuration — Frozen Value

Calculation Parameters

• Time Interval (sec) (calcparm1) — the time span used to determine whether or not the point's value has changed

• If the previous value = current value after expiration of time interval, alarm is set.
• If the previous value ≠current value after expiration of time interval, alarm is not set.

Example

• calcparm1 = 3600

In this example, the Frozen alarm bit is set because the point's value has not changed within the time span specified (3600 sec) in calcparm1.

Alarm Calculation Results — Frozen Value

Frozen Value with Delay

The Frozen Value Delay alarm uses the Frozen Value with Delay (FROZE_VAL_DELAY) calculation. Whenever the time interval is reached, the system calculates the change in engineering units from the newest value older than the time interval and sets the alarm bit if the change is less than the threshold.

Calculation Parameters

• Minimum engineering units threshold (calcparm1) — minimum threshold over the time interval specified in the second parameter

• Time Interval (sec) (calcparm2) — time interval

Equation

Change in Value = ABS(Newest Value Older than Time Interval - Updated Value)

• If Change in Value < calcparm1, alarm is set
• If Change in Value ≥ calcparm1, alarm is not set

Example

• calcparm1 = 10
• calcparm2 = 10

In this example, the Frozen Value Delay alarm bit is set because the change in value (9) is less than the minimum threshold in calcparm1 (10).

• Updated Value = 41
• Previous Value (newest older than time interval) = 50

Change in Value = 50 - 41 = 9

Alarm Calculation Results — Frozen Value with Delay