Understanding the Calculation Editor in Create Mode

When a new calculation or variable is created the Calculation Details takes a different form until the calculation or variable is successfully saved. The title of the Calculation Editor is set to New Calculation or New Variable.

Calculation Details

The Calculation Details consists of the following information:

• The Calculation Device Selection contains the Device Selection details to associate the calculation to a device in the model. See Understanding Device Selection for details. You will not be able to enter any of the other details for the calculation until a network device has been selected.

• The Associated Calculation with a Measurement radio button allows you to determine whether the result of this calculation will be written back to a SCADA measurement or not.

• Selecting No indicates that a calculation will be created and will not be associated with a SCADA measurement on the device.

• Selecting Yes indicates that a calculated measurement will be created and associated with a SCADA measurement on the device.

If a calculation is created as a calculated measurement then the calculation can take advantage all the functionality available to a SCADA measurement e.g.

• Support for alarm generation

• Limits functionality

• Trending

• Historical archiving

• The Calculation Details contains the following information:

• The Name can be entered (for calculations) or selected from a list of available SCADA measurements on the device (for calculated measurements).

• The ID is automatically generated by the system based on the Device and Name.

• The Trigger contains the evaluation type of the calculation and can be one of the following values:

• On Change: The variable is evaluated every time one of its dependencies changes value.

• Periodic: The variable is evaluated periodically.

• On Change and Periodic: The variable is evaluated periodically and every time one of its dependencies changes value.

• The Periodicity is the time between periodic evaluations if the calculation trigger is set to Periodic or On Change and Periodic and can be one of the following values:

• 1 minute

• 5 minutes

• 10 minutes

• 15 minutes

• 30 minutes

• Hourly

• Daily

Variable Details

The Variable Details consists of the following information:

• The Name is the name of the variable.

• The ID is automatically generated by the system based on the Name.

• The Trigger contains the evaluation type of the calculation and can be one of the following values:

• On Change: The variable is evaluated every time one of its dependencies changes value.

• Periodic: The variable is evaluated periodically.

• On Change and Periodic: The variable is evaluated periodically and every time one of its dependencies changes value.

• The Periodicity is the time between periodic evaluations if the calculation trigger is set to Periodic or On Change and Periodic and can be one of the following values:

• 1 minute

• 5 minutes

• 10 minutes

• 15 minutes

• 30 minutes

• Hourly

• Daily

Common Errors

Some of the common errors and issues when creating a new calculation or variable include:

• No device supplied when creating a calculation caused by a device not being selected. See Understanding the Device Selection for details.

• No name supplied caused by not assigning a name to the calculation.

• ID is not unique.

Successful Creation

When the calculation or variable is successfully saved the New Calculation or New Variable editor is closed and a new Calculation Editor is automatically opened whose Title is set to the ID of the newly created calculation or variable.