What is the best way to verify that a piece of equipment is properly grounded?

To verify that a piece of equipment is properly grounded, measuring the resistance between the equipment ground and the main ground lug is the most effective method. This approach allows for a clear assessment of the integrity of the grounding system.

When the resistance is measured, ideally it should be low, typically less than 5 ohms for most equipment. A low resistance value indicates that the grounding pathway is effective, ensuring that any fault current can be safely directed to the ground, thus reducing the risk of electrical shock or fire. If the resistance is high, it may suggest a poor connection or corrosion in the grounding system, which could lead to hazardous conditions.

The other methods, while potentially useful in specific contexts, do not provide as direct or reliable an indication of grounding effectiveness. Measuring current in the ground conductor could show that current is flowing, but it does not confirm that the connection is solid or that the grounding is effective. Touching the metal housing of the equipment gives no quantitative measure of grounding status and could pose safety risks. Disconnecting and reconnecting the ground conductor may inadvertently introduce other issues but does not adequately assess the ground connection's quality.