 Creating conversion tables

The IsaGRAF workbench allows the user to create conversion tables. A conversion table is a set of points used to define an analog conversion. A conversion table can be attached to an analog input or output variable. A table creates a proportional relationship between electrical values (read on input sensor or sent to the output device) and physical values (used in application programming).

Conversion tables are edited through a dialog box run by the "Tools / conversion" command in the ISaGRAF dictionary window

Main commands

Entering points of a table

Rules and limits

A defined conversion table can be used to filter values of any input or output analog variable of the selected project. Attaching a conversion table to a variable is made using commands of the ISaGRAF dictionary, the variables declaration editor. An input or output analog variable must then be selected and its parameters edited. A variable cannot be attached to a conversion table that is not already defined.


Main commands

The "Conversion tables" dialog box shows the list of defined conversion tables, and contains push buttons for main commands, to edit an existing table (define its points), to create a new table, and also to rename or delete a table.

Creating a new table

Changing the contents of a table

Press OK to quit the "Conversion tables" dialog box and save them on disk.


Creating a new table

The "New" command allows the user to create a new conversion table. Up to 127 conversion tables can be created for each project. Only used tables (the ones attached to analog variables) are inserted in the application executable code. Naming a table must conform to the following rules:

•	the name cannot exceed 16 characters

•	the first character must be a letter

•	the following characters can be letters, digits or '_' character

•	the table name is case insensitive


Changing the contents of a table

The "Edit " command is used to enter the points of a table selected from the list. It is also possible to double click on the name of the table. The "Edit" command is automatically called when a new table is created. At least two points must be entered for each table.


Entering points of a table

The "Edit" dialog box allows the user to define the points of a conversion table. The box shows on the left side the list of points already defined. The lower right box shows the defined table as a graphic curve. The points are entered by using the box commands. The user must comply with the number rules for the definition of points, described at the end of this chapter. The box on the left always contains the list of existing points for the currently edited table. The column on the left shows the electrical (external) value of the points. The column on the right shows the physical (internal) values. The user has to select a point on the list in order to modify its values or to clear (remove) it. The last choice of the list ("...   ...") is used to define a new point. The box on the lower right shows the currently edited table as a graphical curve. No axes or coordinates are shown, as this is a proportional representation of the curve. This representation is useful as a quick check that the curve is properly defined.

Defining a new point

Modifying a point

Clearing a point


Defining a new point

When defining a new point, select the last entry ("...   ...") on the list of points. This is also the default mode when starting to define a new conversion table. The user has to enter the electrical (external) and the physical (internal) values of each point. Values are stored as simple precision floating point numbers. Remember that at least two points have to be entered to define a curve. When both values are entered, pressing the "Store" button adds the point to the table. A maximum of  32 points can be defined for each conversion table.


Modifying a point

To modify the values of an existing point, first select it from the list. The new electrical (external) and the physical (internal) values of the point can then be entered. Values are stored as simple precision floating point numbers. When both values are entered, pressing the "Store" button updates the point in the table.


Clearing a point

An existing point is cleared by selecting it from the list and pressing the "Clear" button. Remember that at least two points must be entered to define a table.


Rules and limits

The rules shown below must be followed when defining a conversion table. The table can be used to convert both input and output analog variables:

•	Two points cannot be defined with the same electrical value

•	The curve must be continuously increasing or decreasing

•	Two points cannot be defined with the same physical value

The following limits apply when defining conversion tables for a project:

•	No more than 127 conversion tables can be defined in the same project

•	No more than 32 points can be defined for the same conversion table.