Safety & High Energy#

Mains, high voltage, CAT ratings, isolation, and the habits that prevent injury. This comes first because no measurement matters if someone gets hurt taking it.

• Can I touch/probe this safely? — Assessing hazard before connecting anything. Is it de-energized? Are stored charges drained? What’s the worst case?
• What voltage/energy am I dealing with? — Identifying the energy domain: low-voltage DC, mains AC, high-voltage DC (tube amps, CRTs, switchmode rails), stored energy in capacitors or inductors.
• Do I need isolation or differential measurement? — When a floating measurement will mislead or cause harm. Isolation transformers, differential probes, and when ground-referenced instruments are dangerous.
• Is my instrument rated for this? — CAT ratings, voltage limits, probe ratings, and the difference between a meter that handles a fault and one that becomes shrapnel.
• ESD & Transient Protection Basics — What ESD and electrical transients actually do to ICs, how to handle boards without killing them, and how to design protection into circuits.
• Automotive Electrical Reality (12V Is Not 12V) — What “12V” actually means in a vehicle: voltage swings, cranking brownouts, load dump, reverse polarity, chassis ground behavior, and how to protect circuits that live in cars.