ExclusiveDeviation and NonExclusiveDeviation Alarm types

A "Deviation" alarm type has four intervention thresholds which can be exclusive or non exclusive.

The Threshold values for this type of alarm have a particular meaning according to the settings in the "Deviation Type" parameter. The alarm will behave according to the "Deviation Type" selection as described below. For further information please see the paragraph on "Alarm Prototype Settings".

When the alarm is defined as "Exclusive Deviation" 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 Deviation" 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 exclusion of an alarm is based on its Status, which is also visible in the "Alarm Window", whether the alarm be exclusive or non exclusive.  When an alarm is an Exclusive type, its activation Status will be recorded with the following text:

HighHigh|...

High|...

Low|...

LowLow|...

When an alarm is a 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 to a higher value to the one set in the thresholds. For example, if the four alarm thresholds are set with the following values:

High High Level = 10

High Level = 5

Low Level = -5

Low Low Level = -10

The alarm will trigger with the 'High Level' intervention threshold when the variable's value undergoes a variation of at least 6 positive units, for example if its value switches from 30 to 36.

The alarm will trigger with the "Low Level" intervention threshold when the variable value undergoes a variation of at least 6 negative units, for example if its value switches from 30 to 24.

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 triggerif the Tag undergoes a variation higher to the Tag's percentage value. For example if the four alarm thresholds are set with the following values:

High High Level = 100%

High Level = 50%

Low Level = -50%

Low Low Level = -100%

and the current Tag value is 10, this means that the four intervention threshold 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% di 10) + 10 = 20

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

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

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

By following the example described above the alarm will trigger with the "High Level" intervention threshold when the variable value undergoes a variation of at least 6 positive units, for example if its value passes from 10 to 16. 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.

Deviation Type = PercentOfEURange

When the deviation type is set as the percentage of the scaled value of the engineering unit associated to the Tag (Deviation Type  = PercentOfEURange). The values set in the thresholds will be considered as a percentage value to be applied to the scaled value of the engineering unit associated to the Tag.  The alarm triggers when the tag variation exceeds the percentage value of the difference of the scaled value limits.  For example, if the alarm's four thresholds are set with the following values:

High High Level= 20%

High Level = 10%

Low Level = -10%

Low Low Level = -20%

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

Engineering Unit Low Value = -100
Engineering Unit High Value  = 100
Low Raw Input Value = -50
High Raw Input Value = 50

and the actual value of the Tag is 10, means that the four threshold values will at that moment be calculated with the following values:

High High Threshold = 50

High Threshold = 30

Low Threshold  = -10

Low Low Threshold  = -30

The value is obtained by calculating the difference between the minimum and maximum of the scaled value and then adding the value of the actual Tag.  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 reported above, the alarm will sound with the "High Level" intervention threshold when the variable's value undergoes a variation of at least 21 units in  positive, for example if its value passes from 10 to 31.  The alarm will sound with the "Low Level" intervention threshold when the variable's value undergoes a variation of at least 21 units in negative, for example when its value passes from 10 to -11.

Deviation Type = PercentOfRange

When the deviation type is set as the percentage of the raw value of the Engineering Unit associated to the Tag (Deviation Type  = PercentOfRange) the values set in the thresholds will be considered as the percentage value to apply to the raw value of the Engineering Unit associated to the Tag.  The alarm triggers when the Tag variation exceeds the percentage value of the difference of the raw value limits.  For example, if the four alarm thresholds are set with the following values:

High High Level = 20%

High Level = 10%

Low Level = -10%

Low Low Level  = -20%

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

Engineering Unit Low Value = -100
Engineering Unit High Value  = 100
Low Raw Input Value = -50
High Raw Input Value = 50

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

High High Threshold= 30

High Threshold= 20

Low Threshold= 0

Low Low Threshold= -10

the value is obtained by calculating the percentage of the difference between the minimum and maximum of the raw value and then adding the Tag's actual 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 the alarm will sound with the "High Level" intervention threshold when the variable's value undergoes a variation of at least 11 units in positive, for example if its value passes from 10 to 21.  The alarm will sound with the "Low Level" intervention threshold when the variable value undergoes a variation of at least 11 unit in negative, for example when it's value passes from 10 to -1.