Working with a Linear Diameter Dimension Object on a PCB in Altium Designer

Parent page: PCB Objects

Placed Linear Diameter Dimensions.

Summary

A linear diameter dimension is a group design object. It allows for the dimensioning of an arc or circle with respect to the diameter, rather than the radius. The dimension can be placed either internally or externally.

Availability

Linear Diameter 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 » Linear Diameter from the main menus.
• Click the Linear 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 » Linear Diameter command from the context menu.

PCB Library Editor:

• Choose Place » Dimension » Linear Diameter from the main menus.
• Click the Linear 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. The position of the dimension is determined by the alignment angle for the dimension.
2. Move the dimension text to the desired position (either internal or external) and click or press Enter to complete placement.
3. Continue placing further linear diameter 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 linear diameter dimension object directly in the workspace and change properties such as the position of its text and its reference points, graphically.

When a linear diameter dimension object is selected, the following editing handles are available:

A selected Linear Diameter Dimension.

• Click and drag A or B to adjust the dimension text position parallel to the extensions.
• Click and drag C or D to detach the dimension from the reference object.

If the linear diameter dimension object is totally non-referenced (i.e. it is not attached to a reference design object) click anywhere on it – away from editing handles – and drag to reposition it. While dragging, the linear diameter dimension can be rotated (Spacebar/Shift+Spacebar).

Non-Graphical Editing

The following methods of non-graphical editing are available:

Via the Properties Panel

Properties page: Linear Diameter Dimension Properties

The properties of a Linear Diameter 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 linear diameter dimension object.
• Placing the cursor over a linear diameter 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 linear diameter dimension object can be moved in the following ways:
   1. Selecting both the dimension object and the object that is being dimensioned. The whole can be dragged to a new location as required.
   2. Selecting the object that is being dimensioned only. The dimension text will follow the object in its alignment plane only. The dimension extensions will expand/contract to keep the relationship between dimension and object being dimensioned.
   3. Selecting the dimension object only. It is important to note that the dimension cannot be moved on its own if it is referenced by a design object. To move the dimension only, it must first be detached from the object it is dimensioning.
2. The dimension's value automatically updates as the diameter of the reference arc or circle changes.
3. Linear diameter dimensions are group objects consisting of text and 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.