Wednesday: Multimeter Discipline: The "Deadly Jack" Mistake
A common and dangerous multimeter error is leaving the red test lead in the current jack.
The Core Issue: A common and dangerous multimeter error is leaving the red test lead in the A/mA (current) jack and then probing across a live voltage source.
The Lesson: Current jacks have near-zero internal resistance. Probing a voltage source in this configuration turns the meter leads into a dead short, resulting in a fiery blast.
Actionable Takeaway: Institute a mandatory “pre-probe check.” Say your dial setting out loud and verify lead placement every single time before touching a live circuit.
Post Conclusion
Failure Mode — Do Not Ignore This post describes a failure mode or active hazard. Do not ignore the warning signs described.