Which one is the easiest method for earth resistance measurement?

A. Fall of potential

B. Selective measurement

C. Stake less measurement

D. All are equally easy

Answer: C. Stake less measurement

Explanation: 

• Stake less measurement only measures individual ground rod resistances in parallel to earth grounding systems.
• If the ground system is not parallel to earth, then you will either have an open circuit or be measuring ground loop resistance.
• The most commonly used method of measuring the earth resistance of an earth electrode is the 3-point method or "fall of potential" method.
• It comprises the Earth Electrode to be measured and two other electrically independent test electrodes usually labeled P (Potential) and C (Current).
• An alternating current (I) is passed through the outer electrode C and the voltage is measured, by means of an inner electrode P, at some intermediary point between them.
• A wattmeter is used for the measurement of power.
• Kelvin double bridge is used for the measurement of resistance.
• Schering bridge is used for the measurement of capacitance.