“Text List”

Name of the text list where the alarm message text is saved (see below: “Message”). CODESYS generates the list automatically when you create an alarm group. You can also select an existing text list here.

“Archiving”

Selection of the alarm storage object for the alarm group. When you specify an alarm storage object, CODESYS activates the alarm storage.

“Deactivation”

Boolean variable that deactivates all alarms in this group. CODESYS does not trigger these alarms any longer, even if the alarm condition is fulfilled. Alarms that are already active are not affected by this.

You enter the properties of the individual alarms in the corresponding table columns. Depending on the selected monitoring type, input fields are provided below the table for additionally required parameters.

“ID”

This unique ID corresponds to the ID of the associated text list. You can change the ID in the “ID” field of the table. The ID must always be unique within the alarm group. A change of the ID in the alarm table also directly causes a change in the text list, and the other way around.

“Observation Type”

List box of observation types. Depending on the type, different editing fields are available below the table that define the condition for the alarm. The fields define an expression that triggers the alarm. See the following table.

“Details”

This field shows the configuration settings (defined in the fields below the table) for the selected alarm type.

You can also specify the condition directly into the field. If you input an expression that does not match the currently selected observation type, the type is automatically adapted.

“Deactivation”

(optional) Variable for deactivating the alarm.

“Class”

Assigned alarm class.

“Message”

Required entry of a message text (message) that CODESYS will display in the “Alarm Table” visualization element when the alarm occurs. The text entered here is transferred automatically by CODESYS to the text list for the alarm group. You can insert line breaks by pressing [Ctrl]+[Enter]. CODESYS supports the following placeholders, which are replaced by the actual value at runtime:

‎<DATE>‎

Date of the change to the present status.

‎<TIME>‎

Time of the last status change.

‎<EXPRESSION>‎

Expression (defined within the alarm) that triggered the alarm.

‎<PRIORITY>‎

Priority of the alarm (defined in the alarm class).

‎<TRIGGERVALUE>‎ *

Value that caused the alarm condition to become true.

‎<ALARMID>‎

Alarm ID as displayed in the first column of the alarm table.

‎<CLASS>‎

Name of the alarm class (defined in the alarm).

‎<ALLDEFAULT>‎

Complete information about the alarm is output.

‎<CURRENTVALUE>‎ *

Actual value of the monitored variable.

‎<LATCH1>‎ *

Value of the first latch variable at the time when the alarm was triggered. Note: You can also use more than two latch variables. To do this, insert additional columns from the context menu.

‎<LATCH2>‎ *

Value of the second latch variable at the time when the alarm was triggered.

‎<ALARM>‎

‎TRUE‎ in the case of the alarm status 'Active', ‎FALSE‎ with every other alarm status.

‎<STATE>‎

Alarm status: 0 = 'normal', 1 = 'active', 2 = 'waiting for ACK', 3 = 'active, acknowledged' (still active and already acknowledged)

* For ‎<TRIGGERVALUE>‎, ‎<CURRENTVALUE>‎, and ‎<LATCHn>‎, you can also use formatting specifications such as those which are valid for the C-function ‎printf‎ (example: "‎The value is <CURRENTVALUE %d>‎".

By default, only one column is available for message text. You can add more columns from the context menu which will be available in the “Data type” property for column configuration of the “Alarm Table” and “Alarm Banner” visualization elements.

“Min. Pend. Time”:

Defines the minimum duration for fulfilling the alarm condition so that CODESYS triggers the alarm. In this way, CODESYS can inhibit alarm conditions that occur only for a short time.

IEC 61131-compliant format (example: ‎t#2ms‎).

“Latch var 1”, “Latch var 2”

The latch variables are used to record additional values when the alarm becomes active. A latch variable has to be a scalar type (8-byte) or a ‎STRING‎ or ‎WSTRING‎ type. CODESYS records a latch variable or a latch expression when the alarm becomes active. In this way, it allows additional information about the alarm to be provided.

Note: In “Message”, you can include the information from latch variables in an alarm message. Moreover, you can configure the alarm visualization so that you can filter the displayed alarms by the contents of the latch variables. For more information, see the corresponding help pages below under "See also".

Example: When monitoring a motor speed, the temperature and the current are additionally recorded.

By default, columns are available for two latch variables. You can insert more columns from the context menu which will be available in the “Data type” property for column configuration of the “Alarm Table” and “Alarm Banner” visualization elements.

“Higher prio. alarm”

When the alarm is triggered, it can be acknowledged by triggering another alarm.

Example: A temperature monitor should issue a warning at > 60 °C and an error at > 90 °C. If the temperature rises, then the warning is displayed starting at 60 °C. As of 90° C, the alarm is triggered for the error. This alarm automatically acknowledges the 60° warning.

“Digital”:

“Expression”: Expression to be observed. On the right side, the expression for the comparison. In the middle, you select the desired comparison operator (“=” or ‎<>‎).

“Upper limit”¹⁾:

“Expression”: As described for “Digital”, but with the compare options “>” or ‎>=‎ and optionally a “Hysteresis in %”.

“Lower limit”¹⁾:

“Expression”: As described for “Digital”, but with the compare options “<” or ‎<=‎ and optionally a “Hysteresis in %”.

“Inside range”¹⁾:

“Expression”: Expression to be observed.

“Range”: CODESYS triggers the alarm when the monitored expression is within the range defined here. The left field defines an expression for the lower limit of this range. The right field defines an expression for the upper limit. The expression to be monitored is displayed in the field in-between. You have to set the comparison operators accordingly. You can define a “Hysteresis in %” optionally.

“Outside range”¹⁾:

“Expression”: Expression to be observed.

“Range”: CODESYS triggers the alarm when the monitored expression is outside the range defined here. The left field defines an expression for the lower limit of this range. The right field defines an expression for the upper limit. The expression to be monitored is displayed in the field in-between. You have to set the comparison operators accordingly. You can define a “Hysteresis in %” optionally.

“Change”:

“Expression”: Expression to be observed. CODESYS triggers the alarm when its value changes.

“Event”:

In this case, the application triggers the alarm (event alarm) by using functions from the library ‎AlarmManager.library‎.

¹⁾ For this observation type, you can monitor the specified expression as absolute or relative. Absolute means that the limit value is defined by a fixed value or a variable that returns a fixed value. Relative means that the limit value depends on an expression; for example: upper limit: “Variable x >= 0.9 * y”.

“Hysteresis in %”: When you specify a hysteresis, the alarm condition is fulfilled until a certain deviation from the specified limit value is reached. The size of the deviation is specified as a percentage [%] of the limit value. Example: Upper limit: ‎i_temp >= 30‎ ‎Hysteresis: 10%‎. The alarm is active when the variable ‎i_temp‎ reaches or exceeds the value 30. The alarm is no longer active if the value falls below 27.