Delta Over Time Alarm Calculations
The Delta Over Time alarm calculation types include variations detailed below. They can only 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:
Note: All Calculation Parameters are user-provided.
Delta Value Over Time
The Delta Over Time alarm uses the Delta Value Over Time (DELTA_OVER_TIME) calculation. On each update, the system finds the first value that is older than the time interval specified, calculates the value and time deltas between that value and the updated value, and gets the Delta Over Time rate from those two values. If the absolute value of the Delta Over Time rate exceeds the MaxRate of calcparm1/calcparm2, the alarm is set.
Calculation Parameters
- Maximum EU difference allowed (calcparm1) — maximum allowed change of value over the specified time interval before the alarm is set
- Time Interval (sec) (calcparm2) — the time span used to determine the difference (delta) of the two values
Preliminary Calculations:
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MaxRate = calcparm1/calcparm2
Delta Value = Updated (current) Val - Newest Val Older than Time Interval
Seconds between values = Updated time - Time of Newest Val Older than Time Interval |
Equation
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Delta Over Time = Delta Value / Seconds between values |
- If (ABS) Delta Over Time > MaxRate, alarm is set
- If (ABS) Delta Over Time ≤ MaxRate, alarm is not set
Example
- calcparm1 = 10
- calcparm2 = 30
In this example, the Delta Over Time bit is set because the Delta Over Time rate (0.5384) is greater than the MaxRate (0.333).
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MaxRate = 10/30 = 0.333
Delta = 36 -15 = 21
Seconds between values = 27:10 - 26:31 = 39 sec.
Delta Over Time = 21/39 = 0.5384 (exceeds MaxRate of 0.333, so bit is set) |
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Alarm Calculation Results — Delta Value Over Time |
Delta Value Over Time Positive
The Positive Delta Over Time alarm uses the Delta Value Over Time Positive (DELTA_OVER_TIME_POS) calculation. On each update, the system finds the first value that is older than the time interval specified, calculates the value and time deltas between that value and the updated value, and gets the Delta Over Time rate from those two values. If the Delta Over Time rate exceeds the MaxRate of calcparm1/calcparm2, the alarm is set.
The following image shows the area of an Analog Alarm Settings page of a PNT Editor with an enabled Pos. Delta over Time alarm using the Delta Value Over Time Positive calculation type:
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Alarm Calculation Configuration — Delta Value Over Time Positive |
Calculation Parameters
- Maximum EU difference allowed (calcparm1) — maximum allowed change of value over the specified time interval before the alarm is set
- Time Interval (sec) (calcparm2) — the time span used to determine the difference (delta) of the two values
Preliminary Calculations:
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MaxRate = calcparm1/calcparm2
Delta Value = Updated (current) Val - Newest Val Older than Time Interval
Seconds between values = Updated time - Time of Newest Val Older than Time Interval |
Equation
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Delta Over Time = Delta Value / Seconds between values |
- If Delta Over Time > MaxRate, alarm is set
- If Delta Over Time ≤ MaxRate, alarm is not set
Example
- calcparm1 = 1.01
- calcparm2 = 30
In this example, the Positive Delta Over Time bit is set because the Delta Over Time rate (2.5) is greater than the MaxRate (0.0336).
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MaxRate = 1.01/30 = 0.0336
Delta = 97 - 12 = 85
Seconds between values = 10:15:18 - 10:14:44 = 34 sec.
Delta Over Time = 85/34 = 2.5 (exceeds MaxRate of 0.0336, so bit is set) |
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Alarm Calculation Results — Delta Value Over Time Positive |
Delta Value Over Time Negative
The Negative Delta Over Time alarm uses the Delta Value Over Time Negative (DELTA_OVER_TIME_NEG) calculation. On each update, the system finds the first value that is older than the time interval specified, calculates the value and time deltas between that value and the updated value, and gets the Delta Over Time rate from those two values. If the Delta Over Time rate is less than the negative MaxRate of calcparm1/calcparm2, the alarm is set.
The following image shows the area of an Analog Alarm Settings page of a PNT Editor with an enabled Neg. Delta over Time alarm using the Delta Value Over Time Negative calculation type:
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Alarm Calculation Configuration — Delta Value Over Time Negative |
Calculation Parameters
- Maximum EU difference allowed (calcparm1) — maximum allowed change of value over the specified time interval before the alarm is set
- Time Interval (sec) (calcparm2) — the time span used to determine the difference (delta) of the two values
Note: The maximum EU difference allowed (calcparm1) must be entered as a positive value in the calculations.
Preliminary Calculations:
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MaxRate = calcparm1/calcparm2
Delta Value = Updated (current) Val - Newest Val Older than Time Interval
Seconds between values = Updated time - Time of Newest Val Older than Time Interval |
Equation
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Delta Over Time = Delta Value / Seconds between values |
- If Delta Over Time < - MaxRate, alarm is set
- If Delta Over Time ≥ - MaxRate, alarm is not set
Example
- calcparm1 = 1.01
- calcparm2 = 30
In this example, the Negative Delta Over Time bit is set because the Delta Over Time rate (-0.0571) is less than the -MaxRate (-0.0336).
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MaxRate = 1.01/30 = 0.0336
Delta = 20 - 32 = -12
Seconds between values = 15:07:24 - 15:03:54 = 210 sec.
Delta Over Time = -12/210 = -0.0571 (less than - MaxRate of -0.0336, so bit is set) |
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Alarm Calculation Results — Delta Value Over Time Negative |
