How is a boat's hull potential measured?

The measurement of a boat's hull potential focuses on determining the electrical potential relative to a stable reference point, typically the water in which the boat is floating. This is crucial for troubleshooting electrical issues and ensuring the boat's safety.

Measuring between a reference cell and the engine's negative terminal or its bus is considered the best practice because it provides a clear indication of the potential that the hull presents in relation to a known good reference point. The engine negative terminal commonly serves as a grounding point for many electrical systems on the vessel, and by measuring potential at this location, one can assess the effectiveness of the grounding system and identify any potential electrical faults.

Other options, while they may provide some information, do not offer the same level of clarity or reliability. Measuring at the waterline does not account for variations in water potential caused by different salinity levels. Measuring at the highest point of the hull may not reflect the electrical potential accurately due to distance from the grounding system. Finally, measuring directly at the shore connection is more relevant to the power supply side of the system rather than providing an insight into the hull's potential relative to its own grounding system.