🔍 Key Concepts

• Megohmmeter (megger) operation – what a high resistance vs. low resistance reading means • Difference between a good insulation (no ground) and a direct ground/short to ground • How the scale on an insulation tester is usually marked (zero vs. infinity)

💭 Think About

• When a circuit or cable is properly insulated from ground, should the resistance to ground be very high or very low? How would that appear on a megohmmeter scale? • If a switch or cable is actually grounded (short to ground), would the meter see almost no resistance, or almost infinite resistance between conductor and ground? • Think about what a conventional ohmmeter shows for a dead short between two points. Does a megohmmeter behave similarly in terms of scale direction?

✅ Before You Answer

• Verify which end of the megohmmeter scale corresponds to very low resistance and which to very high resistance (good insulation). • Confirm that a ground fault is essentially a low‑resistance path between conductor and ground. • Make sure you distinguish between a meter that pegs at infinity (open circuit, no continuity) vs. one that drops toward zero (short/ground).