Which mode should never be used as a primary locating method?

• A. Peak Mode
• B. Secondary
• C. Null Mode
• D. Tertiary

Answer: (C)

Locating buried facilities relies on a method that gives a stable, repeatable indication of the line’s position. Peak mode provides the strongest, most consistent signal that aligns with the actual conductor, making it the reliable choice for establishing the location.

Null mode, however, depends on signal cancellation and can occur due to many changing factors—probe orientation, depth, soil conditions, nearby objects, and interference. Because these conditions can shift, the null point isn’t a dependable or precise indicator of where the facility lies. Relying on a null reading can lead to mislocation, so it should not be used as the primary locating method. It may be used only as a supplementary check to confirm or investigate once a more reliable peak-based location is established.