Defining, viewing, and controlling variable groups

Overview

Variable groups can be defined, deleted, viewed, and have their state controlled.

The Variable Groups feature provides the function to:

• Define and start a named variable group which contains one or more device variables
• Read the device variables in the variable group at a defined frequency
• If any of the device variables has changed since their last read, schedule any triggers with the Variable Group trigger event type and the named variable group.

Variable groups are defined on the node where the device variables are accessible.

The Variable Group trigger event type and Data trigger event type are similar in that they monitor the change of the value of a device variable (or multiple device variables). The differences include the number of device variables (single or multiple) and the variable value change conditions.

Defining variable groups

Variable groups are defined after the devices referenced for the device variables are defined and Started.
Follow these steps to add a variable group definition to a node:

1. From the left pane, expand the node that you want to add a variable group definition to.
   
2. Select the Devices icon.
   Then select the Variable Groups tab.
   Or, alternatively, select the Variable Groups sub icon.
   
   The Variable Groups window appears as the right pane.
   For this example, the Variable Groups window has previously defined variable groups.
   
3. From the bottom of the Variable Groups tab, select New.
   A new Variable Group window appears.
   
   
4. Enter a name for the variable group.
   This will be used to identity the variable group in the Variable Group trigger event type.
   
5. Select a value for the Priority (ms) parameter.
   This is the frequency that the runtime Device Publisher feature will read the device variables.
   The units are in milliseconds (ms).
   
6. Select the Add button to add device variables.
   The list of devices are the Started devices on this node.
   Expand the desired device and its internal structure until you can select the individual device variable.
   
   
7. Continue to add device variables to the variable group until you have the complete list desired.
   Each variable has a Key, which will be available to the Variable Group event type trigger as an event variable. This is set to a default value when the variable is added to the group, but can be edited. This variable key can be used as a reference ID, or correlation ID, to help identify which variable's value in the group has changed.
   Variables can be deleted from this list, as well as moved up and down in the list.  The location in the list has no impact on the evaluation of the variable group, it is solely for list readability for the user.
   
   
8. Use the Save button to save the definition of the variable group.
   The variable group will appear in the list of variable groups for the node, in a Stopped state.

Viewing variable groups

The Variable Groups tab provides a list of variable groups defined on the node.

To use the Variable Group tab, follow these steps:

1. From Workbench left pane, expand the node whose variable groups you want to view.
   
2. Select the Devices icon.
   Then select the Variable Groups tab
   Or, alternatively, select the Variable Groups sub icon.
   

3. The Variable Groups tab provides a table format that lists the variable groups defined on the node.
   The top section of the Variable Groups tab provides these columns:

   Column name	Description
   Name	The name of the variable group. This will be used to identity the variable group in the Variable Group trigger event type.
   State	The variable group state, which can be: Started - the variable group is active. The runtime Device Publisher is reading the device variables at the priority frequency. Stopped - the variable group is not active.
   Type	The data type of the device variables.
   Count	The number of device variables when the variable is an array.
   Length	For String data types, the length of the string.

Variable group status information

The bottom portion of the Variable Groups window provides information for the selected variable group as follows:

Variable group Variables section

The Variables section provides information for each of the device variables in the selected variable group as follows:

Controlling variable groups

When a variable group row is selected in the table, the buttons at the bottom of the Variable Groups tab become enabled or disabled. This is based on the current state of the variable group and the function of the button.

A single data variable group row or multiple variable group rows can be selected and then the function buttons used, but the state of each variable group will determine if the function can be performed.

A variable group row's pop-up menu can be displayed, and the available options selected.

Related Topics

Variable Group

Data