Custom Alarms

The following sections detail the calculation, detection, and presentation aspects for the DeltaV custom alarms. For more information on how to configure different alarms, refer to the Alarm Configuration topic.

Custom Alarm Calculation

You can perform your own alarm state calculations using any of the function blocks. Typically, you would use function blocks that support expressions, such as:

• Condition function block
• Calc/Logic function block

The alarm state calculation typically uses logical and relational operators to: test the values in one or more parameters, compute a Boolean result (0 or 1), and write it to a new state parameter.

Custom Alarm Detection

To enable DeltaV alarm features, create an alarm in the same module and attach it to the Boolean state parameter that you computed. At the end of each module execution cycle, the alarms for the module are processed to detect any state changes. When the custom state computation results in a value that is non-zero, the alarm is triggered and is either displayed for the operator or logged in the event log.

Custom Alarm Presentation

DeltaV Operate is the alarm presentation vehicle in the DeltaV system. The presentation is based on the alarm properties and the alarm type. Refer to the Alarm Presentation topic for more details on configuring the alarm presentation.

Adding Custom Alarms

The following sections describe the entire process of creating an expression-based custom alarm. By following the examples, you create the expression (alarm calculation), assign the alarm to the output of the expression (alarm detection) and determine the message to the operator (alarm presentation).

Note You do not have to create your own expression to use custom alarms. You can assign a custom alarm to any Boolean parameter on a function block or module (except unit modules, phase classes, and phase logic modules).

The basic steps for adding an alarm are as follows:

1. In the Alarms view window, click the right mouse button, and then click Add.
2. Select the alarm, click the right mouse button and select Properties.
3. In the Alarm properties dialog box, click the General tab.
4. After entering a name for the alarm, specify the Alarm type and a Priority.
5. In the Alarm parameter field, enter the parameter that triggers the alarm.
6. Select the alarm characteristics as enabled or inverted.
7. Click OK.

Creating a Custom Calculation for the Alarm

Custom alarm calculations must be associated with a parameter that has a value of either 0 or 1. A one (1) indicates an alarm condition, and a 0 indicates a non-alarm condition.

Note If you create your own alarm calculations you must use one of the function blocks that support expressions (for example, the Condition function block or the Calc/Logic function block).

The following example shows how to add a custom alarm to a module using a Condition block. In this example, the user wants to trigger an alarm every time the PV of the AI block is 70 or higher.

Note The custom calculation creates a Boolean parameter that still must be associated with the alarm. This step only sets up the calculation that is associated with an alarm.

To create a custom calculation, perform the following steps:

1. Drag an Analog Input block onto the diagram. The Analog Input block is in the I/O function block category.
2. Drag a Condition block onto the diagram. The Condition block is in the Logical function block category.
3. Click the Condition block.
4. Click the right mouse button and then click Expression.
5. In the Expression Editor dialog, click Insert Internal Parameter.
6. Browse to find the HI_ACT parameter and the CV field in the AI block within this module.
7. Click OK.
8. In the Expression Editor dialog, click the >= symbol.
9. Enter the value 1.
10. Click Parse.
11. When the expression parses without any errors, click OK.

This sets up an expression to see if the HI_ACT parameter is greater than or equal to 70. For this module, the value of the expression is the value of the OUT_D parameter.

Defining the Alarm Detection

Alarm detection is where you identify the parameter that you want to trigger the alarm and you associate that parameter with the alarm.

Using the example in Creating a Custom Alarm Calculation (HI_ACT > 70), define the alarm detection by following these steps:

1. Click the Condition block to select it.
2. Click the right mouse button in the Alarms View window, and then click Add.
3. Enter an alarm name. Make it relevant to the operation.
4. Select the alarm, click the right mouse button and select Properties.
5. Select an Alarm type. For this example, the Any Alarm works.
6. Select the Priority. The Priority of 'Log' only sends the event to the Event Journal and does not display it to the operator.

   Note This step sets the alarm presentation. Refer to the Alarm Presentation topic for more details.

7. In the Related Parameters section, select the Alarm parameter for OUT of the Condition block.
8. Use the Advanced tab to enable or invert the alarm characteristics or change the alarm message parameters (if available).
9. Click OK.

The alarm detection is now defined for the parameter OUT of the Condition block. When the condition of HI_ACT > 70 for the AI block is reached, the output of the Condition block is set to True and the alarm is triggered.

Note If the alarm was inverted, then the alarm is triggered when OUT of the Condition block is set to False.