OPERATION
4-7
Multiple Shorts
If there are multiple shorts between planes, the Direction Arrows will not lead the operator to the short(s)
and a different probing technique must be used as described in this section.
• To determine if multiple plane shorts are present, probe various points on the un-
stimulated plane. Usually a reading of no more than 3.0 will be displayed. If some
readings are 5.0 or more, this suggests there may be multiple shorts between the
planes.
• To locate the multiple shorts, continue to probe the un-stimulated plane (ignoring the
direction arrows) until the highest reading is displayed; one of the shorts will be in this
area.
• Repeat this process until one short remains, then use the method for locating a
single short to locate the final short.
In the event of this being unsuccessful TRACE may be used to locate the shorts individually. (See Section
4.5 — CURRENT TRACING (NON-CONTACT))
Segmented Planes
On some very complex boards, the plane in a layer may be broken into segments making it more difficult
to locate the short circuit.
In this situation it is necessary to study the PCB artwork and treat each segment separately as an
individual plane.
If the arrows direct the user to one of the borders of the stimulated area, it may be assumed that the fault
lies outside the area being probed. In this case move the stimulus probes to the plane segment adjacent
to the indicated border, and repeat the search.
Non-Rectangular Boards
Where the shape of the board is not rectangular it may be difficult to determine the true "corners" of the
plane. In this situation try using four points furthest apart on the board.
Alternatively, divide the board into rectangular sections and treat each section separately. If the arrows
direct the user to the edge of a rectangle and the fault is not evident at this location, stimulate the area
adjacent to that edge.
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