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State Manager – displaying numeric-type tags' values as text

November 8, 2016 | Stepan Drzka

In almost every SCADA project, there are numeric-type tags for which an enumeration of values is defined in advance. These values correspond to respective states of a given element in the monitored industrial process. Let's take a look at an example.


In a control system, there is a tag named Mot_Enum (of type Byte) whose values can be:


Value

State

0

stopped

1

starting

2

running

3

error



While it is suitable, of course, for the user (operator) to display values as text, the systems integrator needs to work with numeric values. This can be solved as follows:


  • Create a second tag (of type String) and use scripts to store a text value in the tag based on a numeric value. However, developing and administering projects with multiple such tags may be a challenging problem. It may also negatively affect the number of data points (license price).

  • For display purposes, use the Active Text component. Although you don't have to create any more tags, this solution is – again – not suitable in terms of project administration because states must be enumerated in each Active Text component. This disadvantage can be partly eliminated by using structured tags and window templates. However, the Active Text component (with or without templates) can be used to display text values only in visualization windows. In alarms/events or reports, it has no effect – only numeric values can be displayed.

  • Define states through the State Manager. This can be done from one place and the display of the states will take effect everywhere.


The State Manager (implemented in Reliance 4.7.3) allows you to define state lists. Each list contains an enumeration of values and the corresponding text.


State Manager, Reliance SCADA

Each numeric-type tag defined through the Device Manager can be linked to a state list defined through the State Manager. The tag value will be automatically converted to text when displayed.


Device Manager, Reliance SCADA


Advantages of using a state list

  • A state list is defined from one place and can be used for any number of tags. This significantly saves time when creating and administering your project.
  • The tag value's textual representation will take effect everywhere – in visualization windows, alarms/events, reports, etc.
  • Individual states' text can be localized into different languages. This means support for multilanguage projects.
  • A state can correspond to either a single value or a range of values.
  • Tags of all numeric data types are supported (including floating-point data types, such as Float).
  • In addition, there is support for array-type tags (values can be displayed, for example, in the Data Grid component).


It is possible to only link text with a value, so far. Other properties, such as the Active Text component's color, are not supported yet. Likewise, it is not yet possible to enter a text value while setting a tag. Hopefully, we will get rid of these two drawbacks in the future.


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