For voltage measurement in a pipe-to-soil potential profile, the voltmeter should be connected how?

• A. Positive to the pipe, negative to the electrolyte
• B. Negative to the pipe, positive to the electrolyte
• C. Positive to both pipe and electrolyte
• D. Negative to both pipe and electrolyte

Answer: (A)

Measuring pipe-to-soil potential involves comparing the pipe’s potential to that of the surrounding soil using a reference electrode in the electrolyte. To read the pipe potential relative to soil, connect the voltmeter’s positive lead to the pipe and the negative lead to the electrolyte. This follows the standard convention where the pipe’s potential is reported with respect to the soil; swapping leads would flip the sign of the reading, which can lead to misinterpretation even though the physical difference remains the same. Using a high-impedance voltmeter and ensuring good contact with the soil helps obtain an accurate, representative measurement.