Alarms Analysis Details#

The Alarms analysis card displays a count of the alarms in your project differentiated by whether they are analog (ALMA) or digital (ALMD) instruction-based alarms or tag-based alarms and alarm definitions. Alarms are used to notify your operators of conditions that they are required to respond to, such as temperature over-limit, excessive current, or a motor failure.

Logix tag-based alarms#

A tag‐based alarm is similar to a digital alarm in that it monitors a tag value to determine the alarm condition. However, a tag‐based alarm is not part of the logic program and does not increase the scan time for a project.

Tip

Tag-based alarms are supported only on CompactLogix 5380, CompactLogix 5480, and ControlLogix 5580 controllers

Alarm definitions#

An alarm definition is associated with an Add‐On Instruction (AOI) or a defined data type. When a tag is created using a data type or an AOI that has alarm definitions, tag-based alarms are created automatically based on the alarm definitions.

The analysis card displays these fields for tag-based alarms and alarm definitions:

  • Use — Indicates whether the alarm is enabled. (Field applies only to tag-based alarms)

  • Required — Indicates whether all instances of alarms based on the alarm definition are enabled. (Field applies only to alarm definitions)

  • Owner — The name of the tag that the alarm is attached to.

  • Name — The name of the alarm or alarm definition.

  • Type — The label for the alarm.

  • Input — The input tag for the alarm. The input tag must be a BOOL, SINT, INT, DINT, or REAL tag, a member of a structured tag, or an element of an array tag.

  • Expression — Determines whether the alarm is triggered when the input is true or false. For Boolean input, when Condition: Expression is set to =1, the alarm is triggered when the input is true. When Condition: Expression is set to =0, the alarm is triggered when the input is false. For analog input, the expression can be set to >, >=, =, <, <=, or <>.

  • Target tag — The tag used to evaluate the alarm’s condition.

  • Class — A name for a category of related alarms or alarm definitions.

  • Alarm group — The name of the group this alarm or alarm definition is a member of.

Instruction-based analog alarms (ALMA)#

An analog alarm defines a condition that evaluates a single analog tag against up to four limit values (high-high, hi, low, and low-low) and up to two rate of change limits (positive and negative). Implemented by the ALMA instruction. Analysis report includes these items:

  • Type — The label for the alarm, such as TRIP, HIHI, or LO.

  • Name — The name of the alarm.

  • Alarm Class — Used to group related alarms.

  • Hi Hi Limit — The value configured for the Hi Hi limit. This value is above the Hi Limit and indicates an increase in the severity of the alarm condition. Many times, these conditions cause the operation to stop or a shut-down timer to start where the operation will shut down if the condition is not resolved.

  • Hi Limit — The value configured for the Hi limit. This value is set at a level that is above the safe operating level for your application. In most cases, this level is of concern but does not require operation to stop and provides adequate time to respond to the condition.

  • Low Limit — The value configured for the Low limit. This value is set at a level that is below the safe operating level for your application. In most cases, this level is of concern but does not require operation to stop and provides adequate time to respond to the condition.

  • Low Low Limit — The value configured for the Low Low limit. This value is below the Hi Limit and indicates an increase in the severity of the alarm condition. Many times, these conditions cause the operation to stop or a shut-down timer to start where the operation will shut down if the condition is not resolved.

  • Min Duration (ms) — Used to enter the length of time an alarm condition must be detected before the alarm is activated.

  • Deadband — With certain kinds of measured values, such as line pressure, tag values can fluctuate rapidly above and below a critical limit. Where such conditions exist, a deadband acts as a buffer zone to keep the fluctuations from re-triggering alarms. For the High and High High alarm conditions, the tag value must drop below the alarm limit minus the deadband before the alarm condition goes Normal (Out of Alarm). For the Low and Low Low alarm conditions, the tag value must go above the alarm limit plus the deadband before the alarm condition goes Normal.

  • Acknowledgment Required — The operator must acknowledge the alarm before it can be cleared.

Instruction-based digital alarms (ALMD)#

A digital alarm monitors a tag for alarm conditions based on whether the tag is equal or not equal to zero. Each value represents a specific alarm condition. Implemented by the ALMD instruction. Analysis report includes these items:

  • Type — The type of the alarm

  • Name — The name of the alarm.

  • Alarm Class — A custom group of alarms based on area, function, testing or other requirements.

  • Condition — The condition to trigger the alarm.

  • Severity — Alarms can range in severity from 1 through 1000 to indicate different levels of importance.

  • Min Duration (ms) — The minimum amount of time in milliseconds that the alarm condition must be true before the alarm condition becomes active.

  • Shelve Duration (ms) — The amount of time in milliseconds that an alarm condition can be temporarily suppressed (shelved).

  • Max Shelve Duration (Min) — The maximum amount of time in minutes for which the alarm can be shelved.

  • Latched — Once triggered the alarm remains in the In Alarm state until reset by the operator.

  • Acknowledgment Required — The operator must acknowledge the alarm before it can be cleared.

You can sort and filter the data in this dashboard. If you want to see the information in a different order, you can reorder the columns in the data table by dragging and dropping them as needed. To help you move around the analysis details page quickly, use keyboard shortcuts.