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4.2 - Variable value components for numeric display

The Channel View certainly provides a quick look at your data, but is not the most convenient or flexible way to display your data, especially once you have more than one channel. In this section we'll add a component to a page that will display data from the Pressure channel. This assumes, of course, that you created an analog Pressure channel in the basic I/O chapter. If you didn't, load the document LJGuideSamples\InputsSimpleWithDA.ctl and start from there.

1) Click on Page_0 in the Workspace under PAGES:.

This will display a blank white page unless you are working off InputsSimpleWithDA. When DAQFactory Express starts, 2 blank pages are generated automatically with default names. With Express you are limited to 2 pages, but with all the other versions of DAQFactory you can create as many pages as you need.

2) Right-click somewhere in the middle of the blank area and select Displays - Variable Value.

This will place a new page component on the screen. There are many different components available that allow you to create custom screens. This particular component simply displays a changing value in text form.

3) Right click on the new component and select Properties...

All of the screen components have different properties windows for configuring the look of the component and telling the component what data to display.

4) Next to Caption: enter Pressure.

The caption is what is displayed in front of your value. A colon is automatically added when displayed.

5) Next to Expression: enter Pressure[0].

Expressions are actually formulas that you can enter to display calculated data. In this case, the formula simply requests the most recent data point of the channel pressure. The [0] indicates the most recent data point. If, for example, we wanted to convert the pressure voltage into actually pressure units, we could put something like Pressure[0] / 5 * 500.

6) Click OK.

Now the screen should display Pressure: 0.42 V with a changing number. This is the current value in the pressure channel we created earlier. Feel free to open the properties window again and play with the units, font and other settings. When you are done, load the sample file listed below as we'll build on it in the next section.

Sample file: LJGuideSamples\VariableValue.ctl