The following example shows a pressureDischarge Tag in the Tag Browser and a Gauge component in the Designer. The value on the Designer component is bound to the Tag and updates in realtime. This is just a simple example of how Tag values can be represented in your SCADA designs.
There are two types of Tag providers; Internal and Remote. By default, a fresh Ignition installation will have an internal Tag provider. This can be thought of as a standard internal Tag database, and stored in the Ignition Gateway. Additionally, it is possible to create Remote Tag Providers, linking one installation of Ignition to the Tags on another Ignition. This ability opens up some very flexible architectures.
Tag User Defined Types (UDTs) provide an object-oriented approach to Tag building, allowing you to define parameterized data types, extend and override types, and then rapidly generate instances. A change to the type definition is then inherited by all instances, drastically saving time when making routine changes. The UDTs are fully supported by Vision templates, which means you can configure templates for your custom data types and take advantage of drag-and-drop binding to rapidly build complex screens.
Tags work naturally and easily with Ignition to offer the following features:
Performance and Scalability
Tags offer great performance on the Gateway, in Perspective Sessions, and in the Vision Client. On the Gateway, the system can support many thousands of value changes per second and millions of Tags. In runtime, Tags improve efficiency with their lightweight subscription architecture. Adding additional Clients creates a nearly negligible effect on the database and the Gateway performance.
Use Tag UDTs (User Defined Types) to design re-usable, parameterized, and extendable data types. You can create and configure new instance Tags in seconds, saving a great amount of time over traditional Tag systems.
Powerful Alarming Model
Each Tag can have any number of alarms configured on it. There are many different alarm modes accommodating simple digital alarms, analog high/low value alarms, as well as more specialty alarms like bad data quality and bit-packed alarms. The settings for alarms can bound to other Tags, making the alarm configuration dynamic.
Drag-and-Drop Screen Design
You can drag and drop Tags onto a window or view to automatically create new bound components. Drag Tags onto existing components or properties to quickly bind them to the data.
Ignition Tags can easily be imported and exported from the Designer by selecting the More Options menu, then either the Import Tags icon or Export Tags icon. You'll be prompted to choose the Tags or folders that you want. See the Exporting and Importing Tags page for more information.
Tags names are flexible and to not have to match data source names (like an OPC path) or tag codes (such as N7, F8, etc.). It is not necessary that Tag's name be related at all to its underlying data source (OPC path, for instance). This provides a level of indirection that is convenient for systems with many repeat Tag structures.
It is important to give Tags a meaningful structure and arrange them in hierarchical Tag folders so that they are easy to understand, identify, and locate for all developers. By default, Ignition Tags are named after their OPC Server address when a Tag is dragged into the Tag Browser. You can change this name to just about anything that you want. We recommend using names that mean something to your process, such as "Motor 3 Amps." Alternatively you could create folders in your Tag Browser such as "Motor 3/Amps.". When renaming Tags and folders, there is really only one question to ask: "does this structure make sense?"
Another important concept to consider when naming and organizing your Tags, is to do this early in your project. If you rename or move any of your Tags to another folder, and your Tag is being used in other places, chances are you are going to break the reference to the Tag on your screen. So keeping your Tags organized and defining your Tag structure early on in your project is critical.
When you choose a new name for your Tags and folders, there are some rules that must be followed. The first character of the Tag name must be one of the following:
The second character, and every character after that can then be one of the following:
Any of the following special characters:
All other special characters are not allowed in a Tag name.