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Examoogle • User • info@examoogle.com • EE-2024-8821
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How much current is generated in the earth tester?
50 V DC
500 V AC
50 V AC
500 V DC
500 V DC
Quick Summary: An earth tester, specifically the Megger-type earth resistance tester, utilizes a built-in hand-driven DC generator to supply the necessary voltage for testing. It typically generates a DC voltage of 500 V to measure the resistance of grounding systems by injecting current into the soil and measuring the potential drop.
An earth tester, specifically the Megger-type earth resistance tester, utilizes a built-in hand-driven DC generator to supply the necessary voltage for testing. It typically generates a DC voltage of 500 V to measure the resistance of grounding systems by injecting current into the soil and measuring the potential drop.
Re=IV — Earth resistance definition where V is the applied potential and I is the test current.
P=V×I — Power rating of the generator utilized for the test.
The device operates on the principle of a cross-coil ohmmeter. The hand-driven DC generator creates 500 V DC, which is passed through a current reverser to produce an alternating current (AC) in the earth circuit to prevent polarization effects in the soil, while the internal potential coil system operates in DC to provide a direct resistance reading.
Earth testers use a DC generator to ensure independence from external power supplies.
The 500 V DC level is standard for high-voltage testing of insulation and ground electrodes.
The current is often rectified or reversed to AC within the unit to avoid soil electrolysis.
Higher voltages are used to ensure reliable measurement across high-resistance soil conditions.
Portable and self-contained operation.
Provides reliable results regardless of mains supply availability.
Requires manual operation if hand-cranked.
Higher voltages require careful handling to avoid insulation breakdown.
Grounding system resistance measurement.
Site soil resistivity testing for power system commissioning.
While the output voltage is 500 V DC, the actual current flowing through the ground is kept in the milliampere range to ensure safety.
Option C (50 V AC) is incorrect as it is insufficient for standard earth resistance testing protocols.
D is correct — The standard earth tester utilizes a 500 V DC generator to provide the excitation voltage required for accurate resistance measurement.
Always remember that earth testers use high voltage DC to overcome contact resistance at the probes, ensuring that the measured value reflects the true soil resistance.