Which instrument would you use to check the grounding path impedance to earth in a building?

Which instrument would you use to check the grounding path impedance to earth in a building?

• A. Ground Loop Impedance Tester
• B. Megger
• C. Volt-Ohm Meter
• D. Receptacle Tester

Answer: (A)

Measuring grounding path impedance to earth is about evaluating the fault loop impedance so that protective devices will trip quickly in a fault. The instrument built for this task is a ground loop impedance tester. It purposely injects a known test current and measures the resulting voltage to calculate the impedance of the path from the live conductor through the protective device back to earth. This lets you verify that the earth fault loop meets the required limits for safe operation and meets trip-time specifications. A megger is mainly used to test insulation resistance (and sometimes basic continuity), not to assess the live fault loop impedance under typical operating conditions. A volt-ohm meter can measure resistance and voltage but doesn’t reliably evaluate the fault loop impedance in the field. A receptacle tester checks wiring correctness of outlets, not the impedance of the grounding path.

Measuring grounding path impedance to earth is about evaluating the fault loop impedance so that protective devices will trip quickly in a fault. The instrument built for this task is a ground loop impedance tester. It purposely injects a known test current and measures the resulting voltage to calculate the impedance of the path from the live conductor through the protective device back to earth. This lets you verify that the earth fault loop meets the required limits for safe operation and meets trip-time specifications.

A megger is mainly used to test insulation resistance (and sometimes basic continuity), not to assess the live fault loop impedance under typical operating conditions. A volt-ohm meter can measure resistance and voltage but doesn’t reliably evaluate the fault loop impedance in the field. A receptacle tester checks wiring correctness of outlets, not the impedance of the grounding path.