Difficulty: Easy
Correct Answer: current tracer, logic pulser
Explanation:
Introduction / Context:Finding shorts on a dense digital PCB can be challenging. Rather than guessing, technicians use targeted tools to excite the circuit and observe where current actually flows. The right combination makes it quicker to track the fault to a specific trace or component.
Given Data / Assumptions:
Concept / Approach:A logic pulser momentarily drives a pin or net with controlled pulses at logic levels. A current tracer (a handheld probe with a magnetic or resistive sensor) detects the resulting pulse current through traces, allowing you to follow it physically across the board. When a short exists, the current concentrates near the fault, producing a stronger indication and guiding you to the exact location.
Step-by-Step Solution:
Isolate the suspect net and remove power to sensitive loads if needed.Attach the logic pulser to the node to inject low-duty-cycle pulses.Sweep the current tracer along the trace path, watching for signal strength increase.Identify the point where current abruptly diverts or peaks—this is near the short.Verification / Alternative check:Technicians corroborate by lifting components or cutting jumpers near the indicated spot; continuity tests (DMM) confirm the short after the board cools and the stimulus is removed.
Why Other Options Are Wrong:
Logic pulser + logic probe: the probe reads logic levels, not current flow along traces.Logic probe/clip: useful for state observation, but not for tracing shorts.Current tracer + logic clip: the clip is a powered logic indicator, not a stimulus source.Common Pitfalls:Overdriving the node with an improper pulser setting; misinterpreting inductive pickup from adjacent power rails as the short path; forgetting to disconnect heavy loads that mask the short’s signature.
Final Answer:current tracer, logic pulser
Discussion & Comments