Adding a Design Variable in RMxprt

A design variable is associated with an RMxprt design. A design variable can be assigned to a parameter value in the RMxprt design in which it was created.

1. Click RMxprt > Design Properties.

Alternatively, right-click the design name in the project tree, and then click Design Properties on the shortcut menu.

The Properties dialog box appears opened on the Local Variables tab. From the Properties dialog you can Add, Add Array, Edit, or Remove variables.



Any existing Design variables are listed in the Properties dialog with the name followed by cells for Value, Unit, Evaluated Value, Type, Description, and Read-only and Hidden check boxes. A Show Hidden check box on the lower right of the Properties dialog controls the appearance of any Hidden variables.

Initially, leave the radio button with Value selected until you have defined a variable. The other radio buttons let you enable defined variables for Optimization/Design of Experiments, Tuning, Sensitivity or Statistics. Selecting one of these radio buttons adds a new column to the Variable definition row for which you can check or uncheck Include for regular variables for that kind of Optimetrics simulation.

2. Click Add.

The Add Property dialog box appears.

3. In the Name box, type the name of the variable.

Variable names must start with a letter, and may include alphanumeric characters and underscores ( _ ). The names of intrinsic functions and the predefined constant pi (p) cannot be used as variable names.

You can sort the variables by clicking on the Name column header. By default, variables are sorted in original order. Clicking once sorts them in ascending order, noted by a triangle pointing up. Clicking against sorts in descending order, noted by a triangle pointing down. Clicking a third time sorts in original order, with no triangle.

4. Select a radio button for the variable use:
   

   Selected Use	Setable Properties
   Variable	Unit Type, Units, Value
   Array Index Variable	Associate Array variable, Value
   Separator	Value
   Post Processing Variable	Unit Type, Units, Value

   
   

Each selection affects the settable options.

5. In the Unit Type text box you can use the drop-down menu to select from the list of available unit types. “None” is the default.

When you select a Unit Type, the choices in drop-down menu for the Units text box adapt to that unit type. For example, selecting Length as the Unit Type causes the Unit menu to show a range of metric and US units for length. Similarly, if you select the Unit Type as Resistance, the Units drop down lists a range of standard Ohm units.

6. In the Value box, type the quantity that the variable represents. Optionally, include the units of measurement.
Note: If you include the variable's units in its definition (in the Value box), do not include the variable's units when you enter the variable name for a parameter value.

The quantity can be a numerical value, a mathematical expression, or a mathematical function. The quantity entered will be the current (or default value) for the variable. If the mathematical expression includes a reference to an existing variable, this variable is treated as a dependent variable. The units for a dependent variable will automatically change to those of the independent variable on which the value depends. Additionally, dependent variables, though useful in many situations, cannot be the direct subject of optimization, sensitivity analysis, tuning, or statistical analysis.

Note: Complex numbers are not allowed for variables to be used in an Optimetrics sweep, or for optimization, statistical, sensitivity or tuning setups.
7. Click OK.

You return to the Properties dialog box. The new variable and its value are listed in the table. If the value is an expression, the evaluated value is shown. Updating the expression also changes the evaluated value display. The evaluated values of any dependent variables also are changed.


8. Optionally, type a description of the variable in the Description box.
9. You can designate a variable as Read-only, Hidden, or Sweep. You may need to use the scroll bar or resize the dialog to view the check boxes.


The Sweep check box lets you designate variables to include in solution indexing as a way to permit faster post processing. Variables with Sweep unchecked are not used in solution indexing. If a solution exists, checking or unchecking a variable’s Sweep setting produces a warning that the change will invalidate existing solutions. To continue, click OK to dismiss the warning dialog.

If a variable has dependent variables, the Sweep check box is disabled and cannot be changed.


10. Click OK.

The new variable can now be assigned to a parameter value in the design in which it was created.