3.2 Using the Color Fill Drawing Method to Display the Value of the Analog Input Tag
Having created a tag, you can now use a drawing method to represent it on the application page.
In the preceding exercise, you entered all of the properties necessary for the analog input tag to locate and accept the incoming analog data from the booster tank. Your tag is already reading this data; however, you cannot see this data until you create a graphic to display it.
In this exercise, you will see all of the available drawing methods for analog input tags, and will use the Color Fill drawing method to indicate the booster tank level.
The Tag Browser should currently be open and should be displaying the newly created analog input tag. If it is not, open the Tag Browser using the Configuration Toolbox, and select Analog Input from the Types drop-down list. The new tag "AI20_1" will be highlighted in the tag list of the Tag Browser.
1. Click the Draw button in the Tag Browser. The Analog Input tag drawing methods display in a dialog as shown in Figure 28.
Figure 28
There are a wide variety of drawing methods that can be used to display the value of an analog input tag. Because your tag is already reading data via the virtual Modicon PLC, each of the analog input tag drawing methods displayed is indicating the current booster tank level, and this value is fluctuating on your screen. Note that each drawing method shown displays a blinking question mark, indicating that the value of the tag has not yet been validated (i.e. is questionable data).
In your tutorial system, you will be portraying the booster tank level value visually as a rising and falling water level using the Color Fill drawing method.
2. Click the Color Fill button on the Analog Input dialog. (you may need to scroll down through the options)
3. You will be prompted to place a sample image of a Color Fill on the page. Place it in the center of the Booster Station application page.
The Color Fill Graphic Editor opens.
Figure 29
There are three parts to a color fill:
• The bar color represents the value of the tag: in this case it will represent water in the tank, so you will set it to be pale shade of blue.
• The unfilled color represents that part of the tank that has not yet been filled. A background color such as black makes a good choice for this.
• The changed color is an optional feature of this drawing method. If set, then the bar color and the background color will only be visible when placed on top of the matching "changed" color. This can be useful for defining an irregular shape to make it appear that the fluid level is visible only through a crack.
4. Click the Bar Color button.
The Select Color palette opens in free color mode (i.e. as the mouse pointer moves across the palette and page, the color in the sample area changes accordingly). As you may remember, we worked with the Select Color palette previously when we were configuring the background color for the Booster Station application page.
Figure 30
5. Click an aqua color using the mouse pointer. The sample color window displays the selected color (Figure 30).
6. Click the OK button to close the Select Color dialog.
7. Click the Unfilled Color button. The Select Color dialog re-opens.
8. Select the navy blue color, then click on OK.
Figure 31
The Scaling parameter does not need to be changed: You will use the tag's scaled minimum and maximum values as shown.
9. Click the OK button to close the Graphic Editor.
10. Click the Close button to close the Tag Browser.
11. Click the close button in the Configuration Toolbox's title bar. The Configuration Toolbox closes. The system is now in operation mode.
The drawing method is now visually displaying the changing incoming analog values of the analog input tag representing the booster tank level: the bar color is moving up and down as the data changes.
Place your mouse pointer over the object. A tooltip opens and identifies the tag associated with this object by showing the tag's name and description as in Figure 32.
Figure 32
Note the question mark. This indicates that the data is questionable since it has not yet been validated against the actual equipment. This is a default behavior. The Questionable property (appearing on the Merit tab) for all newly created tags is initially set to "1" or true until validation has occurred. This feature helps ensure that all equipment and tags are carefully checked during commissioning to be certain that data is accurate. We will discuss questionable data and commissioning in lesson 16.
Your Booster Station application page should now appear similar to Figure 33.
Figure 33
Alone, the Color Fill drawing method is not very intuitive. In the next lesson you will add graphics that will add context to the value being displayed.
Skills Achieved in Lesson 3
You achieved the following skills and knowledge in Lesson 3:
• In order to establish a connection between a basic I/O tag and the associated equipment, the tag must be connected to a device driver tag which is in turn associated with a port tag. This relationship facilitates communications with the outside system.
• Not only does the Tag Browser facilitate the creation of new tags, it provides access to the tools you need to display their values on the screen.
• The Draw button of the Tag Browser opens the drawing methods associated with the selected tag based on its tag type;
• Each of the tag drawing methods enables you to tailor its appearance according to the way you wish to use it to portray the value of the tag;
• Each newly created tag has a Questionable property which is set to "1" or true, indicating that the value of the tag has not been tested. The result is that the drawing objects representing the tag will be marked with a question mark until the data has been tested and the Questionable property has been set to "0" or false;
• When the mouse pointer is placed over a drawing object representing a tag, a tooltip appears and identifies the name and description of the tag as you defined them when creating that tag.