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A LabVIEW Datalogging and Supervisory Control (DSC) Module application typically consists of three components: front panels that you use to view and interact with data, shared variables that represent I/O data, and supervisory programs that implement custom I/O logic. Some advanced DSC Module applications implement a fourth component, a system configuration management program, that programmatically configures the DSC Module application. You can organize the components of a DSC Module application in a LabVIEW project.

The Shared Variable Engine (SVE) manages and provides access to shared variables. All DSC Module applications use both LabVIEW and the SVE.

Front Panels

Use front panels to interact with and display information about the state of a supervisory control and data acquisition system. You can use front panels as a user interface to display information about a VI. The DSC Module also extends front panel capability by enabling front panel data binding to reduce the amount of time you need to spend developing block diagrams.

Refer to the Heat Exchanger VI in the labview\examples\lvdsc\Applications\Heat Exchanger directory for an example of an application that uses front panel data binding.

In addition to front panel data binding, the front panel of the Heat Exchanger VI also uses several user-interface-related features of the DSC Module. For example, the front panel includes buttons that launch other front panels. The front panel also uses industrial automation images that the Image Navigator provides.

Shared Variables and I/O Servers

Shared variables form the basis for the I/O model in the DSC Module. Each shared variable represents one I/O point. You can bind a shared variable to a single I/O source. You can configure data logging, alarming, and security settings for shared variables. Use LabVIEW projects and LabVIEW project libraries to organize hierarchies of shared variables in a DSC Module application.

You can use shared variables with or without data binding. With data binding, a data source automatically updates the shared variable value. The DSC Module includes several I/O servers, including OPC Client and Modbus I/O servers, that you can use to acquire data from programmable logic controllers or other similar devices.

Supervisory Programs

Most DSC Module applications implement some form of supervisory control. For example, you can monitor alarms on shared variables and then perform a task when the alarm occurs. You also can monitor a set of input shared variables bound to an I/O server, reduce the data, and then write the output to another set of shared variables. A more complex example of supervisory control is PC-based control of a process or of multiple processes.

One way to write a supervisory control application in the DSC Module is to write a VI that reads from a set of shared variables in a While Loop and performs some action on the data. However, maintaining the application can be difficult using this static data access method. Instead, you can use DSC Module tools, such as custom I/O servers, and dynamic data access methods to build flexible and maintainable supervisory control applications.

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