A center dimension is a group design object. It allows for the center of an arc or circle to be marked.
Center dimension objects are available for placement in the PCB Editor only. Use one of the following methods to access a placement command:
Choose Place»Dimension»Center from the main menus.
Click the button on the Place Dimension drop-down () of the Utilities toolbar.
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:
Position the cursor and click or press Enter to anchor the dimension to the desired arc or circle.
Move the dimension until the desired sizing is achieved then click or press Enter to complete placement.
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 anti-clockwise 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 propertiesdialog, from where properties for the dimension can be changed on-the-fly.
While attributes can be modified during placement (Tab to bring up associated properties dialog), bear in mind that these will become the default settings for further placement unless the Permanent option on the PCB Editor – Defaults page of the Preferences dialog is enabled. When this option is enabled, changes made will affect only the object being placed and subsequent objects placed during the same placement session.
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 & drag A to change the size of the dimension. As you drag a handle, the dimension may be rotated (Spacebar/Shift+Spacebar).
If attempting to graphically modify an object that has its Locked property enabled, a dialog will appear asking for confirmation to proceed with the edit. If the Protect Locked Objects option is enabled on the PCB Editor – General page of the Preferences dialog, and the Locked option for that design object is enabled as well, then that object cannot be selected or graphically edited. Double click on the locked object directly and disable the Locked property or disable the Protect Locked Objects option, to graphically edit the object.
The following methods of non-graphical editing are available:
This method of editing uses the following dialog to modify the properties of a center dimension object.
The Center Dimension dialog.
The Center Dimension dialog can be accessed prior to entering placement mode, from the PCB Editor – Defaults page of the Preferences dialog. This allows the default properties for the center dimension object to be changed, which will be applied when placing subsequent center dimensions.
During placement, the dialog can be accessed by pressing the Tab key.
After placement, the dialog 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.
Using the Edit»Change command and clicking once over a placed center dimension object.
Quickly change the units of measurement currently used in the dialog between metric (mm) and imperial (mil) using the Ctrl+Q shortcut. This affects the dialog only and does not change the actual measurement unit employed for the board, as determined by the Measurement Unit setting in the Board Options dialog (Design » Board Options).
The PCB Inspector panel enables the designer to interrogate and edit the properties of one or more design objects in the active document. Used in conjunction with appropriate filtering - by using the PCB Filter panel, or the Find Similar Objects dialog - the panel can be used to make changes to multiple objects of the same kind, from one convenient location.
The PCB List panel allows the designer 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 the designer to target and edit multiple design objects with greater accuracy and efficiency.
A center dimension object can be moved in the following ways:
Selecting both the dimension object and the circle/arc that is being dimensioned. The whole can be dragged to a new location as required.
Selecting the circle/arc that is being dimensioned only. The dimension will move with the object.
When the reference arc or circle to which a center dimension object is attached is deleted, a dialog will appear, asking whether the dimension should also be deleted. If the dimension is not deleted, it remains in the workspace, but non-referenced. Note however that a non-referenced center dimension cannot be attached to another circle/arc.
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.