Test Instruments: Meters, Meggers, and Safe Verification

You can't start up or troubleshoot a system without measuring it correctly — and safely. These are trade-practice/physics facts (not tied to a single CEC section).

1. The multimeter — how you connect it matters

• Voltage is measured in parallel — leads placed across the two points.
• Current (with an in-line ammeter) is measured in series — the meter carries the circuit current. (A clamp-on ammeter avoids this: it reads current by sensing the magnetic field around a single conductor, no contact needed.)
• Resistance / continuity must be measured on a de-energized circuit — testing resistance on a live circuit gives false readings and can damage the meter.

2. Specialty testers

• Insulation-resistance tester ("megger"/megohmmeter): applies a high DC voltage (typically 500 V–5 kV) and reads insulation quality in megohms — used to find breaking-down insulation.
• Non-contact voltage tester: detects the presence of voltage without touching a conductor (a quick first check — not an exact measurement).