A baseline dimension is a group design object. It allows for the dimensioning of a linear distance of a collection of references, relative to a single base reference. The first point chosen is the 'base'. All subsequent points are relative to this first point. The dimension value in each case is, therefore, the distance between each reference point and the 'base', measured in the default units. The references may be objects (tracks, arcs, pads, vias, text, fills, polygons, or components) or points in free space.
Baseline dimension objects are available for placement in the PCB or PCB Footprint Library editor by choosing Home | Dimension | Dimension then selecting Baseline from the drop-down list.
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 then click or press Enter to anchor the dimension start point (this is the first reference point or 'base').
- Move the cursor to the required endpoint then click or press Enter to anchor the dimension endpoint (this is the second reference point).
- The text can now be initially positioned. Click or press Enter when the text is in the desired position to effect placement.
- Move the cursor to subsequent reference points then click or press Enter twice to effect placement (first click to anchor to a reference and second click after positioning the text).
- When all required references in the baseline dimension have been covered, 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 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.
- While attributes can be modified during placement (Tab to bring up the associated Inspector panel), keep in mind that these will become the default settings for further placement.
This method of editing allows you to select a placed baseline dimension object directly in the workspace and change properties such as the position of its text and its reference points graphically.
When a baseline dimension object is selected, the following editing handles are available:
- Click & drag the handles at arrows to adjust the dimension text position parallel to the extensions.
- Click & drag A to move the base point of the dimension.
- Click & drag subsequent handles to move each reference individually with respect to the base.
If the baseline dimension object is totally non-referenced (i.e. it is not attached to any reference design objects) click anywhere on it away from editing handles and drag to reposition it. While dragging, the baseline dimension can be rotated (Spacebar/Shift+Spacebar) or mirrored (X or Y keys to mirror along the X-axis or Y-axis respectively).
The Inspector panel enables you to interrogate and edit the properties of one or more design objects in the active document. Used in conjunction with appropriate filtering, the panel can be used to make changes to multiple objects of the same kind, from one convenient location.
- A baseline dimension object can be moved in the following ways:
- Selecting both the dimension object and the objects that are being dimensioned. The whole can be dragged to a new location as required.
- Selecting an 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.
- 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 objects it is dimensioning.
- The dimension's value automatically updates as its start or endpoints are moved. Likewise, if the position of an object that a reference point of the dimension is anchored to is changed, the dimension will update and expand/contract to reflect this.
- When the reference or references to which a dimension object is attached are deleted, a dialog will open asking whether the dimension should also be deleted. If the dimension is not deleted, it remains in the workspace, but non-referenced.