ExclusiveRateOfChange and NonExclusiveRateOfChange Alarm types

A "Rate Of Change" alarm type has four intervention thresholds.  In this case the thresholds can be exclusive of non exclusive.

For this type of alarm the threshold values obtain a certain significance according to the "Deviation Type" parameter. In addition it is also necessary to set a sample time interval using the "Time Unit" parameter. Based on the "Deviation Type" selection the alarm will behave as described below. For further information please also refer to the paragraph on "Alarm Prototype Settings".

When the alarm is defined as "Exclusive Rate Of Change" type, each intervention threshold will be exclusive, therefore when the "High High" threshold activates the "High" threshold deactivates. When the alarm is defined as  "NonExlusive Rate Of Change" type, the intervention threshold will not be exclusive. Therefore when, for example, the "High High" threshold activates so will the "High" threshold. In Runtime the discrimination of an alarm is based on its Status, which is also visible in the "Alarm Window", whether the alarm be exclusive or nonexclusive. When an alarm is Exclusive type, its activation Status will be recorded with the following text:

HighHigh|...

High|...

Low|...

LowLow|...

When an alarm is Non Exclusive, its activation Status will be recorded with the following text:

HighHighActive|...

HighActive|...

LowActive|...

LowLowActive|...

Deviation Type = AbsoluteValue

When the deviation type has an absolute value (Deviation Type = AbsoluteValue), the alarm intervenes only when the Tag value changes with a variation higher than the value set in the time interval samples in the thresholds specified with the "Time Unit". For example, if the four alarm thresholds and the "Time Unit" are set with the following values:

High High Level = 10

High Level = 5

Low Level = -5

Low Low Level = -10

Time Unit = 5 sec

The alarm will go off with the "High Level" intervention threshold when the variable value undergoes a variation of at least a positive of 6 units in the range of 5 seconds. The 5 seconds count starts immediately upon the first Tag variation. As soon as the Tag exceeds the value of the defined threshold the alarm will go off. However, if this threshold value is not exceeded within 5 seconds, the counter will reset and restart upon the next Tag variation.  By taking the example setting described above, if the Tag value passes from 30 to 36 in less than 5 seconds, the "High Level" threshold will go off.  Analogously, the alarm will go off with the  "Low Level" intervention threshold when the variable  undergoes a variation of at least 6 negative units, for example if its value passes from 30 to 24 within the range of 5 seconds.

When a Rate of Change alarm is activated, it will remain active even when its value stops changing. At this point, after the "Time Unit" time has elapsed and acknowledged by the user, its state will set to "Inactive".

Deviation Type = PercentOfValue

When the deviation type is set as a percentage of the value (Deviation Type = PercentOfValue) the values set in the thresholds will be considered as percentage values to be applied to the Tag value. The alarm will go (activates) off if the Tag undergoes a variation higher to the Tag's percentage value in the sample time interval specified with the "Time Unit". For example if the four alarm thresholds and the "Time Unit" are set with the following values:

High High Level = 100

High Level = 50

Low Level = -50

Low Low Level = -100

Time Unit = 5 sec

and the current Tag value is 10, this means that the four intervention thresholds will instantly be calculated with the following values:

High High Threshold = 20

High Threshold  = 15

Low Threshold = 5

Low Low Threshold = 0

the value is established by taking the percentage rate of the Tag value and then adding it to actual Tab value itself. For example:

High High Threshold = (100% of 10) + 10 = 20

High Threshold = (50% of 10) + 10 = 15

Low Threshold = -(50% of 10) + 10 = 5

Low Low Threshold = -(100% of 10) + 10 = 0

By following the example described above the alarm will go off with the "High Level" intervention threshold when the variable value undergoes a variation of at least 6 positive units within the range of 5 seconds. The 5 second count starts immediately upon the first Tag variation. As soon as the Tab value exceeds the defined threshold value, the alarm will go off. However, if this threshold value is not exceeded within 5 seconds, the counter will reset and restart upon the next Tag variation. By taking the example setting described above into consideration, if the Tag value passes from 10 to 16 in less than 5 seconds, the "High Level" threshold will go off. Analogously, the alarm will go off with the  "Low Level" intervention threshold when the variable undergoes a variation of at least 6 negative units, for example if its value passes from 10 to 4 in the range of 5 seconds.

When a Rate of Change alarm is activated, it will remain active even when its value stops changing. At this point, after the "Time Unit" time has elapsed and acknowledged by the user, its state will set to "Inactive".

Deviation Type = PercentOfEURange

When the deviation type is set as a percentage of the EU Range value of the Engineering Unit associated to the Tag (Deviation Type = PercentOfEURange) the values set in the thresholds will be considered as the percentage value to be applied to the UE Range of the Engineering Unit associated to the  Tag. The alarm goes off if the Tag variation is higher than the percentage value of the limit differences of UE Range in the time interval sample specified with the "Time Unit". For example, if the four alarm thresholds and the "Time Unit" are set with the following values:

High High Level = 20

High Level = 10

Low Level = -10

Low Low Level = -20

Time Unit = 5 sec

and the Engineering Unit associated to the Tag has the following values:

EU Range Low = -100

EU Range High= 100

Instrument Range Low = -50

Instrument Range High = 50

and the actual value of the Tag is 10, means that the four intervention thresholds will be calculated with the following values:

High High Threshold = 50

High Threshold = 30

Low Threshold = -10

Low Low Threshold = -30

The value is established by taking the percentage of the difference from the minimum and maximum value of the EU Range and then adding it to the same actual Tag value. For example:

High High Threshold = (20% di (100 - (-100))) + 10 = 50

High Threshold = (10% di (100 - (-100))) + 10 = 30

Low Threshold = -(10% di (100 - (-100))) + 10 = -10

Low Low Threshold = -(20% di (100 - (-100))) + 10 = -30

By following the example described above the alarm will go off with the "High Level" intervention threshold when the variable value undergoes a variation of at least 21 positive units within the range of 5 seconds. The 5 second count starts immediately upon the first Tag variation. As soon as the Tab value exceeds the defined threshold value, the alarm will go off.  However, if this threshold value is not exceeded within 5 seconds, the counter will reset and restart upon the next Tag variation. By taking the example setting described above into consideration, if the Tag value passes from 10 to 31 in less than 5 seconds, the "High Level" threshold will go off. Analogously, the alarm will go off with the "Low Level" intervention threshold when the variable  undergoes a variation of at least 6 negative units, for example if its value passes from 10 to -11 in the range of 5 seconds.

When a Rate of Change alarm is activated, it will remain active even when its value stops changing. At this point, after the "Time Unit" time has elapsed and acknowledged by the user, its state will set to "Inactive".

Deviation Type = PercentOfRange

When the deviation type is set as a percentage of the Instrument Range value of the Engineering Unit associated to the Tag (Deviation Type = PercentOfEURange) the values set in the thresholds will be considered as the percentage value to be applied to the Instrument Range of the Engineering Unit associated to the Tag. The alarm goes off if the Tag variation is  higher than the percentage value of the limit differences of Instrument Range in the time interval sample specified with the "Time Unit". For example, if the four alarm thresholds and the "Time Unit" are set with the following values:

High High Level = 20

High Level = 10

Low Level = -10

Low Low Level = -20

Time Unit = 5 sec

and the Engineering Unit associated to the Tag has the following values:

EU Range Low = -100

EU Range High= 100

Instrument Range Low = -50

Instrument Range High = 50

and the actual Tab value is 10, means that the four thresholds will be calculated with the following values at that moment:

High High Threshold = 30

High Threshold = 20

Low Threshold = 0

Low Low Threshold = -10

the value is established by taking the percentage of the difference between the minimum and maximum values of the Instrument Range and adding it to the Tag value. For example:

High High Threshold = (20% di (50 - (-50))) + 10 = 30

High Threshold = (10% di (50 - (-50))) + 10 = 20

Low Threshold = -(10% di (50 - (-50))) + 10 = 0

Low Low Threshold = -(20% di (50 - (-50))) + 10 = -10

By following the example above reported, the alarm will go off with the "High Level" intervention threshold when the variable value undergoes a variation of at least 11 positive units, for example if its value passes from 10 to 21. The alarm will go off with "Low Level" when the variable value undergoes a variation of at least 11 negative units, for example if its value passes from 10 to -1.

By following the example described above the alarm will go off with the "High Level" intervention threshold when the variable value undergoes a variation of at least 11 positive units within the range of 5 seconds. The 5 second count starts immediately upon the first Tag variation. As soon as the Tab value exceeds the defined threshold value, the alarm will go off.  However, if this threshold value is not exceeded within 5 seconds, the counter will reset and restart upon the next Tag variation. By taking the example setting described above into consideration, if the Tag value passes from 10 to 21 in less than 5 seconds, the "High Level" threshold will go off. Analogously, the alarm will go off with the "Low Level"  intervention threshold when the variable  undergoes a variation of at least 6 negative units, for example if its value passes from 10 to -1 in the range of 5 seconds.

When a Rate of Change alarm is activated, it will remain active even when its value stops changing. At this point, after the "Time Unit" time has elapsed and acknowledged by the user, its state will set to "Inactive".