Remote Automation Solutions Guide: OpenEnterprise Expression Editor Reference Guide Manuals & Guides

Reference Guide

D301489X412
April 2012

OpenEnterprise Expression Editor
Reference Guide (V2.83)

Remote Automation Solutions

Website: www.EmersonProcess.com/Remote

Reference Guide

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Expression Edito

Contents

1 Expression Editor....................................................................................................................1

1.1 Expression Editor................................................................................................................1

1.1.1 Tag................................................................................................................................2

1.1.2 Default Return Value....................................................................................................2

1.1.3 Conditions List Box.......................................................................................................2

1.1.4 Remove Condition........................................................................................................3

1.2 Edit Condition......................................................................................................................3

1.2.1 Condition Operator.......................................................................................................3

1.2.2 Comparison Value........................................................................................................3

1.2.3 Return Value.................................................................................................................3

2 Index .........................................................................................................................................4

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1 Expression Editor

The Expression editor allows the user to configure conditions to an OPC tag. As the conditions are
built up using a graphical interface, an 'expression' is created.

In programming terms, a typical expression could have the meaning - "If the value of the OPC tag is
greater than X then this property equals Y, if the value of the OPC tag equals A then this property
equals B, else this property equals C". Simply, then, by selecting a tag and attaching conditions to it,
an 'expression' is built.

Currently, the only OpenEnterprise component that makes use of the Expression editor is the Trend
View. The Trend View uses expressions to control the colour of a pen's line and markers (see the
example below).

In the display below, the pen and the marker are drawn in green while the value is greater than 75 or
while the value is less than -50, otherwise they default to red.

1.1 Expression Editor

This dialog enables you to configure Expressions which will control the color of the Pen depending on
its value.

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1.1.1 Tag

This edit box contains the OPC/HDA tag that describes the expressions data source. Tags can be
entered manually, dragged and dropped from other applications or obtained from the OE Tag Browser
by clicking on the browser button to the right of this edit box.

For an example of how to drag-drop a realtime tag into a field see the Drag Drop Realtime Tag into
Data Source Field topic.

For an example of how to drop a historical tag into this field see the Drag Drop a Historical Tag into a
Field topic.

Alias Support
OE Expressions may contain aliases in either the tag edit box or the comparison value edit box.

Aliases enable tags to be passed dynamically, based on user selection from one OE Component to
another. More information on passing aliases as parameters between OE Component s may be found
in the OE Menus help file.

1.1.2 Default Return Value

If none of the conditions are true then the returned value of the expression will be this value, which is
the colour property of the selected Pen. Selection of the colour square will open a colour selector,
which enables the user to change the default colour.

1.1.3 Conditions List Box

This list box details the conditions that are attached to the expression. The conditions are evaluated in
the order they appear going from top to bottom. This list box allows the user to change the order of
the conditions (and hence the order of precedence) by dragging and dropping each condition to a new
location in the list.

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1.1.4 Remove Condition

Removes the currently selected condition from the Conditions List.

1.2 Edit Condition

This dialog enables you to configure the condition, value and returned Pen color for an Expression.

1.2.1 Condition Operator

This list provides a selection of conditions or operators for the expression. The conditions available
are:-

• Equal to;

• Greater than;

• Greater than or equal to;

• Less than;

• Less than or equal to;

• Not equal to.

1.2.2 Comparison Value

This should be typed into the Comparison value field. It is the value that the Expression Editor will use
to compare the current value of the tag in the Tag field using the Condition Operator.

1.2.3 Return Value

If the coloured button is selected, a colour selection dialog is opened, and the user may choose a
different Return Value colour.

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2 Index

1

C

Comparison Value.............................................. 5

Condition Operator............................................. 5

Conditions List Box ............................................ 4

D

Default Return Value.......................................... 4

E

Edit Condition Dialog.......................................... 5

Expression Edito

Expression Editor Dialog ....................................3

Expression Editor Overview................................3

R

Remove Condition ..............................................4

Return Value.......................................................5

T

Tag......................................................................4

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