This dialog allows the designer to specify the properties of a Linear Dimension object. A linear dimension is a group design object. It places dimensioning information on the current PCB layer, with respect to a linear distance. The dimension value is
the distance between the start and end markers (reference points selected by the user) measured in the default units. The references may be objects (tracks, arcs, pads, vias, text, fills, polygons or components) or points in free space.
For information on how a placed linear dimension object can be modified graphically, directly in the workspace, see Graphical Editing.
The Linear 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 linear dimension object to be changed,
which will be applied when placing subsequent linear dimensions.
During placement, the dialog can be accessed by pressing the Tab key.
While attributes can be modified during placement, 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.
After placement, the dialog can be accessed in one of the following ways:
Double-clicking on the placed linear dimension object.
Placing the cursor over the linear dimension object, right-clicking and choosing Properties from the context menu.
Using the Edit»Change command and clicking once over the placed linear dimension object.
Pick Gap - the current pick gap value, which is is the distance between a dimension extension line and the object being dimensioned.
Extension Width - the current width for the dimension extension lines.
Arrow Size - the current arrowhead size. The size is measured as the distance between the arrow tip and the end of the arrow 'legs'.
Arrow Length - the current arrow length. Note that the value entered into this field is applied only when the Arrow Position is set to Outside.
Line Width - the current arrow line width (the "thickness" of the lines used to produce the arrows).
Offset - the current arrow offset with respect to the dimension extension line. The offset is the distance between the arrow tip and the end of the extension line furthest from the object being dimensioned. If the value is increased,
the extension line extends by the additional amount in order to meet the offset criteria.
Rotation - the angle of alignment of the dimension, measured anti-clockwise in degrees from the horizontal.
Text Height - the current height of the dimension text characters. The character width used to display or print the text is automatically proportioned to this height. A minimum height of 36mil (0.9mm) will allow
the string to be legibly photoplotted.
Text Width - the current dimension text stroke width (the "thickness" of the lines used to produce the lettering).
Text Gap - the current gap to the left and right of the dimension value text.
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).
Layer - the layer the dimension is currently assigned to. Dimensions can be assigned to any available layer, click on the list to view and select a different layer, from all those currently defined for the board.
Unit - the current unit that is selected for the calculation and display of the dimension value. Choose either Mils, Millimeters, Inches, Centimeters, or Automatic.
The Automatic setting follows the actual measurement unit employed for the board, as determined by the Measurement Unit setting in the Board Options dialog (Design » Board Options).
Format - the current setting for the format of the dimension text. Use the associated drop-down to change the format as required. The options listed will depend on the chosen Unit and present based on the actual value
for the current dimension. In generic terms, the available options are:
None - no dimension text is displayed.
Value Only - no units are displayed, only the dimension value (eg. 600.00).
Value and Unit - units are displayed after the dimension value (eg. 600.00mil).
Value and Bracketed Unit - units are displayed in brackets after the dimension value (eg. 600.00(mil)).
Precision - the current setting for the number of decimal places to the right of the decimal point that the dimension will be displayed to. The maximum number of decimal places is 6.
Text Position - the current position of the dimension text. Use the associated drop-down list to choose one of the following options:
Automatic - the dimension text will be placed in the most appropriate location with respect to the dimension, such that the text itself is always readable.
Aligned - Center - the dimension text will be aligned to the center of the dimension line.
Aligned - Top - the dimension text will be aligned above the dimension line, and centered.
Aligned - Bottom - the dimension text will be aligned below the dimension line, and centered.
Aligned - Right - the dimension text will be aligned to the right of the dimension line (outside of the extension line).
Aligned - Left - the dimension text will be aligned to the left of the dimension line (outside of the extension line).
Aligned - Inside Right - the dimension text will be aligned to the right of the dimension line (inside the extension line).
Aligned - Inside Left - the dimension text will be aligned to the left of the dimension line (inside the extension line).
Unidirectional - the dimension text will be aligned to the center of the dimension line, but will remain horizontal, irrespective of the dimension alignment angle.
Manual - the dimension text will be available for manual placement by the user, directly in the workspace.
Prefix - the current prefix to the dimension value.
Arrow Position - the current position of the dimension arrows. The available options are:
Inside - the arrows will be positioned inside the dimension's extension lines (pointing outwards).
Outside - the arrows will be positioned outside the dimension's extension lines (pointing inwards).
If the Text Position is set to Automatic, the Arrow Position field will be disabled.
Suffix - the current suffix to the dimension value.
Locked - enable this option to protect the dimension from being edited graphically.
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.
Sample - this field presents a sample of how the dimension text will appear, in accordance with specified Format, and any defined Prefix and/or Suffix.
Font - use this field to choose the type of font used for the dimension's text, either Stroke or TrueType. The dialog will present options based on the chosen type.
Select Stroke Font
This area of the dialog and its asscociated option are presented only when the Stroke option is chosen for the dimension text's Font.
Font Name - use this field to choose the required Stroke font. Available options are Default, Serif, and Sans Serif. The Default style is a simple vector font which supports pen plotting and vector
photoplotting. The Sans Serif and Serif fonts are more complex and will slow down vector output generation, such as Gerber.
Stroke-based fonts are built into the software and cannot be changed. All three fonts have the full IBM extended ASCII character set that supports English and other European languages.
Select TrueType Font
This area of the dialog and its asscociated options are presented only when the Truetype option is chosen for the dimension text's Font.
Font Name - use this field to choose the required TrueType font. The drop-down list is populated with TrueType and OpenType (a superset of TrueType) fonts found in the \Windows\Fonts folder. Note, the list will only include
entries for detected (and uniquely named) root fonts. For example, Arial and Arial Black will be listed but Arial Bold, Arial Bold Italic, etc will not. Use the Bold and Italic options to add emphasis to the text.
Bold - enable this option to make the dimension text bold.
Italic - enable this option to make the dimension text italic.
The use of TrueType fonts in PCB documents will result in more complex Gerber outputs.
To ensure all fonts used in your design are available wherever the design is loaded, enable the Embed TrueType fonts inside PCB documents option, on the PCB Editor - TrueType Fonts page of the Preferences dialog.
A substitution TrueType font can also be nominated, for files using TrueType fonts that are not installed locally.