Working with a Center Dimension Object on a PCB in Altium Designer

Parent page: PCB Objects

A placed Center Dimension.

Summary

A center dimension is a group design object. It allows for the center of an arc or circle to be marked.

Availability

Center dimension objects are available for placement in both the PCB editor and the PCB Library editors in one of the following ways:

PCB Editor:

• Choose Place » Dimension » Center from the main menus.
• Click the Center Dimension button () in the drop-down on the Active Bar located at the top of the workspace. (Click and hold an Active Bar button to access other related commands. Once a command has been used, it will become the topmost item on that section of the Active Bar.)
• Click the  button on the Place Dimension drop-down () of the Utilities toolbar.
• Right-click in the workspace then choose the Place » Dimension » Center command from the context menu.

PCB Library Editor:

• Choose Place » Dimension » Center from the main menus.
• Click the Center Dimension button () in the drop-down on the Active Bar located at the top of the workspace. (Click and hold an Active Bar button to access other related commands. Once a command has been used, it will become the topmost item on that section of the Active Bar).

Placement

After launching the command, the cursor will change to a cross-hair and you will enter dimension placement mode. Placement is made by performing the following sequence of actions:

1. Position the cursor and click or press Enter to anchor the dimension to the desired arc or circle.
2. Move the dimension until the desired sizing is achieved then click or press Enter to complete placement.
3. Continue placing further center dimensions, or right-click or press Esc to exit placement mode.

Additional actions that can be performed during placement are:

• Press the + and - keys (on the numeric keypad) to cycle forward and backward through all visible layers in the design respectively – to change placement layer quickly.
• Press Spacebar to rotate the dimension counterclockwise or Shift+Spacebar for clockwise rotation. Rotation is in accordance with the value for the Rotation Step, defined on the PCB Editor – General page of the Preferences dialog.
• Press the Tab key to access an associated properties panel, from where properties for the dimension can be changed on-the-fly.

Graphical Editing

This method of editing allows you to select a placed center dimension object directly in the workspace and change its size and orientation, graphically.

When an center dimension object is selected, the following editing handles are available:

A selected Center Dimension.

• Click and drag A to change the size of the dimension. As you drag a handle, the dimension may be rotated (Spacebar/Shift+Spacebar).

Non-Graphical Editing

The following methods of non-graphical editing are available:

Via the Properties Panel

Properties page: Center Dimension Properties

The properties of a Center Dimension can be edited in the PCB editor's Properties panel, which allows editing of all item(s) currently selected in the workspace.

During placement, the panel can be accessed by pressing the Tab key.

After placement, the properties can be accessed in one of the following ways:

• Double-clicking on a placed center dimension object.
• Placing the cursor over a center dimension object, right-clicking and choosing Properties from the context menu.

Via a List Panel

Panel page: PCB List, PCB Filter

The PCB List panel allows you to display design objects from one or more documents in tabular format, enabling quick inspection and modification of object attributes. Used in conjunction with appropriate filtering - by using the PCB Filter panel, or the Find Similar Objects dialog - it enables the display of just those objects falling under the scope of the active filter – allowing you to target and edit multiple design objects with greater accuracy and efficiency.

Tips

1. A center dimension object can be moved in the following ways:
   1. Selecting both the dimension object and the circle/arc that is being dimensioned. The whole can be dragged to a new location as required.
   2. Selecting the circle/arc that is being dimensioned only. The dimension will move with the object.
2. Center dimensions are group objects consisting of track segments. They can be converted to their set of primitive objects by choosing Tools » Convert » Explode Dimension to Free Primitives from the main menus. Once exploded, a dimension object can no longer be manipulated as a group object.