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 both the PCB editor and the PCB Library editors in one of the following ways:
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 design space. (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 design space 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 design space. (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).
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 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.
While attributes can be modified during placement (Tab to open the Properties panel), keep 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 design space and change its size and orientation, graphically.
When a 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).
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, that object cannot be graphically edited. Double-click the locked object to select it then disable the Locked property in the Properties or List panel or disable the Protect Locked Objects option to graphically edit the object.
The following methods of non-graphical editing are available.
Editing via the Center Dimension Dialog or Properties Panel
This method of editing uses the associated Center Dimension dialog and Properties panel mode to modify the properties of a Center Dimension object.
The Center Dimension dialog (the first image) and the Center Dimension mode of the Properties panel (the second image)
During placement, the Center Dimension mode of the Properties panel can be accessed by pressing the Tab key. Once the Center Dimension is placed, all options appear.
After placement, the Center Dimension dialog can be accessed by:
Double-clicking on the placed Center Dimension object.
Placing the cursor over the Center Dimension object, right-clicking then choosing Properties from the context menu.
After placement, the Center Dimension mode of the Properties panel can be accessed in one of the following ways:
If the Properties panel is already active, select the Center Dimension object.
After selecting the Center Dimension object, select the Properties panel from the Panels button at the bottom right of the design space or select View » Panels » Properties from the main menus.
If the Double Click Runs Interactive Properties option is disabled (default) on the PCB Editor – General page of the Preferences dialog, when the primitive is double-clicked or you right-click on a selected primitive then choose Properties, the dialog will open. When the Double Click Runs Interactive Properties option is enabled, the Properties panel will open.
While the options are the same in the dialog and the panel, the order and placement of the options may differ slightly.
Press Ctrl+Q to toggle the units of measurement currently used in the dialog/panel between metric (mm) and imperial (mil). This only affects the display of measurements in the dialog/panel; it does not change the measurement unit specified for the board, which is configured in the Units setting in the Properties panel when there are no objects selected in the design space.
The Center Dimension properties 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.
Editing Multiple Objects
The Properties panel supports editing multiple objects, where the property settings that are identical in all currently selected objects may be modified. When multiples of the same object type are selected manually, via the Find Similar Objects dialog or through a Filter or List panel, a Properties panel field entry can be edited for all selected objects. If values of a property are different for objects in the selection, the appropriate field will be shown as an asterisk (*) – a new property value will be applied to all selected objects.
A 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 applicable 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.
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.
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.