Alarm Formula
- 05 Feb 2024
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Alarm Formula
- Updated on 05 Feb 2024
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The Alarm Formula determines the logic used by Alarm Server to assess violations. Each type of alarm has its own formula that requires configuration by the user. Most of the values in the Formula column surrounded by square brackets are supplied by the user. See each formula’s subsection for more information.
Type | Default Name | Description | Formula |
|---|---|---|---|
MinMax | Alarms when tag value is outside of specified limits. | [TAG] > [MAX LIMIT] OR [TAG] < [MIN LIMIT] | |
SQC | Alarms when tag value is outside of SQC limits. | [TAG] >[SQC MAX LIMIT] OR [TAG] < [SQC MIN LIMIT] | |
SQCHA | Alarms when tag hourly average is outside of SQC limits. | [TAG HOURLY AVERAGE] > [SQC MAX LIMIT] OR [TAG HOURLY AVERAGE] < [SQC MIN LIMIT] | |
Custom1 | Alarms when tag value or constant is greater or less than other tag value or constant, and/or tag value or constant is greater or less than other tag value or constant. | [TAG OR CONSTANT] >/< [TAG OR CONSTANT] AND/OR [TAG OR CONSTANT] >/< [TAG OR CONSTANT] | |
Custom2 | Alarms when tag value is greater or less than other tag value or constant for a period of time. | [TAG] >/< [OFFSET] >/< [TAG OR CONSTANT] FOR LONGER THAN [TIME SPAN] | |
Custom3 | Alarms when tag value is greater or less than other tag value or constant for longer than a period of time within a period of time. | [TAG] >/< [OFFSET] >/< [TAG OR CONSTANT] FOR LONGER THAN [TIME SPAN] IN [TIME SPAN] | |
Custom4 | Alarms when tag value is greater or less than other tag value or constant for more than number of times. | [TAG] >/< [OFFSET] >/< [TAG OR CONSTANT] MORE THAN [TIMES] | |
Custom5 | Alarms when tag value is greater or less than other tag value or constant for more than number of times within a period of time. | [TAG] >/< [OFFSET] >/< [TAG OR CONSTANT] MORE THAN [TIMES] IN [TIME SPAN] | |
Custom6 | Alarms when tag value is greater or less than other tag average for period of time. | [TAG] >/< [TIME SPAN] AVERAGE OF [TAG] >/< [OFFSET] FOR LONGER THAN [TIME SPAN] | |
Custom7 | Alarms when ratio of two tags or a tag value and a constant is greater or less than other tag value or constant. | [TAG OR CONSTANT] DIVIDED BY [TAG OR CONSTANT] >/< [TAG OR CONSTANT] | |
Custom8 | Alarms when tag value changes by more than some constant in period of time. | [TAG] CHANGE BY [CONSTANT] IN [TIME SPAN] | |
Custom9 | Alarms when tag average is greater or less than other tag value or constant. | [TIME SPAN] AVERAGE OF [TAG] >/< [TAG OR CONSTANT] | |
Custom10 | Alarms when any tag which matches specified mask is in alarm. | TAG WITH NAME LIKE [MASK] IS IN ALARM | |
Custom11 | Alarms when tag value has not changed for longer than specified period of time. | [CURRENT TIME] – [VALUE CHANGE TIME] > [TIME SPAN] | |
Custom12 | Alarms when tag has not had new points for longer than specified period of time. | [CURRENT TIME] – [LAST POINT TIME] > [TIME SPAN] | |
Composite | Alarms when any member of composite alarm is in alarm. | ANY COMPOSITE MEMBER IS IN ALARM |
Absolute Deadband Min/Max
An Absolute Deadband Min/Max alarm enters the ON state if the tag’s value is greater than or less than fixed values. The alarm can be set to alarm inside the values instead of outside.
Deadbanding can be enabled by checking Enable OFF Deadband. If set, the alarm does not enter the OFF state until it passes the Max-Deadband or Min+Deadband value.
SQC
An SQC alarm allows alarming based on a tag’s pre-configured SQC limits. This setting works for grade-based and non-grade-based limits. If any of the SQC counting rules are enabled for that tag, the Reset Counters on Filter ON means that when the filter tag resets the alarm or turns the alarm off, it resets any of the counting based rules.
SQC Hourly Average
The SQC Hourly Average alarm provides SQC or limited based alarming based on the tag’s hourly average.
Min/Max
A Min/Max alarm enters the ON state when a tag's value is greater than or less than or equal to another tag's value or a constant and/or another tag's value is greater than or less than or equal to another tag's value or a constant. It is only necessary to fill in one set of values before the And/Or operator.
Min/Max for Duration
A Min/Max for Duration alarm enters the ON state when a tag's value is greater then, less than or equal to another tag's value or a constant value for longer than a fixed period of time.
The first field must be a tag; the second field can be a tag or a constant.
Min/Max for Duration in Period
A Min/Max for Duration in Period alarm enters the ON state when the tag’s value is greater than or less than another tag’s value or a constant value for a period of time during a period of time.
The first field must be a tag; the second field can be a tag or a constant.
Min/Max for Count
A Min/Max for Count alarm enters the ON state when a tag’s value is greater than or less than another tag’s value or a constant from more than a specified number of times. This alarm is normally used with lab data or test data, not process data.
The first field must be a tag; the second field can be a tag or a constant.
Min/Max for Count in Period
A Min/Max for Count in Period alarm enters the ON state when a tag’s value is greater than or less than another tag’s value or a constant from more than a specified number of times during a period of time. This alarm is to be used with lab data or test data, not process data.
The first field must be a tag; the second field can be a tag or a constant.
Min/Max for Other Tag Average
A Min/Max for Other Tag Average alarm enters the ON state when the tag’s value is greater than or less than the average of another tag for a period of time.
Ratio of Tags
A Ratio of Tags alarm enters the ON state if a tag’s value divided by another tag’s value or a constant value is greater than or less than another tag or constant.
The first field must have a tag; the other two fields can be tags and/or constants.
Max Allowable Change in Period
A Max Allowable Change in Period alarm checks the change in the value of a tag over a period of time. In the drop-down menu, the alarm can be set to only enter the ON state if the tag’s value increases OR decreases.
The first field must be a tag; the second field can be Changes, Decreases, or Increases; and the other fields are constants.
Min/Max for Tag Average
A Min/Max for Tag Average alarm checks to see if a tag’s average over a period of time is greater than or less than another tag’s value or a constant value.
The first two fields are constants for Hours and Minutes and the third must be a tag; the last field can be a tag or constant.
Matching Alarms Active
A Matching Alarms Active alarm enters the ON state when any tag with text that matchers the string entered in the first field is in the ON state. For example, if all the PM1 tags have "PM1" in the name and "PM1" is entered here, this tag will alarm if any of the tags with "PM1" in the name alarm.
Tag Not Changing Value
A Tag Not Changing Value alarm enters the ON state when a tag’s value has not changed for longer a period of time. This alarm is used to monitor tags that should be changing, and can also be used to monitor heart-beat tags from sources.
The first field requires a Tag and the second field requires a time in Hours:Minutes:Seconds format.
Tag Not Getting New Points
A Tag Not Getting New Points alarm enters the ON state when a tag has not had a new value with a new timestamp in a period of time. This alarm is used to monitor tags that should have a new point in history, but not necessarily a different value. It can also be used to monitor heart-beat tags from sources.
The first field requires a Tag and the second field requires a time in Hours:Minutes:Seconds format.
Composite
A Composite alarm allows users to build a tiered alarm based on several existing alarms. Members of the composite alarm are assigned a priority that affects how simultaneous events are handled. The higher the priority (“1” is highest), the greater precedence will be placed on the alarm. For example, if a Priority 2 alarm is open, then a Priority 1 alarm begins, the composite alarm will end the first event and start a new event. It will also reset the alarm rule. Overlapping alarm events of the same priority will not cause splitting of the composite event.
The deadband, split logic, and uptime settings do not affect composite alarms. The composite alarm will instead respect these settings as configured for its member alarms. For example, if a Priority 1 alarm splits, the composite alarm will also be split.
To add or remove alarms from a composite alarm, expand the Add/Remove Members section. Select alarms in the Available Alarms panel and click Add, or select alarms in the Members panel and click Remove.
Assign a Priority to a member alarm by entering a number in the Priority column. “1” is the highest priority. Multiple member alarms can have the same priority.
The Detection Period affects how far into the past the Alarm Server will look each cycle to assess whether to modify composite events. This is most applicable when using SQC counting rules or when defining alarms for manual entry tags.
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