Part 2: Introduction to Tags and Folders

Introduction

In Fernhill SCADA Tags represent the resources in the SCADA system. For example:

A Data Point Tag is a measured value.
A PLC Device Tag is a programmable logic controller.
A Channel Tag is a communication path to a device.
A Graphic Page Tag is a graphic page showing the state of equipment.
A Trend Plot Tag is a historic plot of process variables.

You use the Tag Window of the Configuration Tool to edit tags:

Tags are organized using folders, which is similar to the way files are organized in a file system. You can use folders to group together logically related tags. For example:

A piece of equipment
A plant floor
A building
A geographical location

Aims of this Section

In this part of the Getting Started Guide you will use the Configuration Tool to:

Create new tags.
Edit tag properties.
Monitor the status of tags.

You will create tags to monitor these signals from a pump:

Signal	Type	Description
PumpState	Digital	Whether the pump is running (TRUE) or stopped (FALSE).
Current	Analog	The current consumption of the pump in Amps.

Tags and Folders

In the Tag Window, right-click the database root folder localhost. Then select Add New Folder:

When you create a new folder or new tag, a new name is automatically generated. For information on how to rename tags, and which characters are valid in tag names see Tag Window Tag Names.
Enter the name Getting Started then press Return:
Right-click the new folder Getting Started the select Add new tag, followed by Core and then IEC 61131-3 Program. Press Return to accept the default name for the program:

This example will use an IEC 61131-3 Program Tag to simulate the pump operation.
Double-click the IEC 61131-3 Program Tag to open the text editor:

When you create a new IEC 61131-3 Program, a default template is provided. Press CTRL-A to select all text in the program. Then press DEL to delete the default template. In the next step you will add the code to generate test data.

Copy and paste the following code into the text editor:

Var_Global
    (* These global variables will be the data source for the data point tags *)
    PumpRunning : BOOL;
    MotorCurrent : LREAL;
End_Var

Program Main
    VAR 
        Timer : TON; 
        RandomValue : WORD;
    End_Var

    (* Use a TON function block to trigger every 5 seconds... *)
    Timer( IN:=NOT Timer.Q, PT:=t#5s );

    (* If the timer has elapsed... *)
    If Timer.Q Then
    
        (* Get a random value *)
        RandomValue := SysGetRandomWord();

        (* Work out the new pump state *)
        If RandomValue < 16#8000 Then
        
            (* Pump stopped *)
            PumpRunning := FALSE;
            MotorCurrent := 0.0;
        
        Else

            (* Pump running *)
            PumpRunning := TRUE;
            MotorCurrent := 15.0 + TO_LREAL(RandomValue AND 16#FFF) / 4096.0;
        
        End_If
    End_If
End_Program

This code should replace the default template provided when you created the IEC 61131-3 Program Tag.

Click the Save icon in the toolbar. Check there are no errors reported in the Status Views Window:

If there are errors shown, go back to step 5 and check the code was pasted correctly.

Close the program code window.
In the Tag Window, right-click the Getting Started folder and select Add new tag, followed by Core, then I/O Digital Tag. Set the name of the tag to Pump State:
In the Properties Window, click the Browse Button of the IODataSource property. A dialog opens allowing you to choose the tag that will provide the data to the I/O Digital Data Point Tag:

Note: Make sure the Relative Reference field is checked.

In this example an IEC 61131-3 Program is the data source. In a real application the data source would be a PLC Device Tag or other type of data source.
Select IEC 61131-3 Program and click OK. In the Properties Window, click the Browse Button of the IOItemName property. A dialog opens allowing you to choose the program variable to use as the data source for the I/O Digital Data Point Tag:
Select PumpRunning and click OK. Enter these additional values in the Properties Window:

Property Value

TextState0 Stopped

TextState1 Running

The values in the Properties Window should now look like this:

The IODataSource property is reference property and allows one tag to refer to another tag. In Fernhill SCADA there are two types of reference value:
- A relative reference, which starts with a full stop (.) character. The target of a relative reference is worked out starting from the current folder.
- An absolute reference, which does not start with a full stop (.) character. The target of an absolute reference is worked out starting from the root folder.
Relative references are an important concept in Fernhill SCADA and will be described more in Part 5: Copying and Pasting.
Check the status of the new I/O Digital Data Point Tag in the Status Views Window:
In the Tag Window, right-click the Getting Started folder and select Add new tag, followed by Core, then I/O Analog Tag. Set the name of the tag to Motor Current:
In the Properties Window, set these properties of the Motor Current tag:

Property Value

IODataSource .IEC 61131-3 Program

IOItemName MotorCurrent

IOItemType 32-bit floating point

Units Amps

When complete, the properties should look like:
Check the status of the new I/O Analog Data Point Tag in the Status Views Window: