Ground Loop Voltage

The voltage you're measuring (1-2 volts) is called "ground loop voltage." It occurs when electrical circuits share a common ground path, but have different voltage potentials.

Causes

In your case, the neutral wire from your branch circuit (the outlet) is connected to the neutral bus in the sub-panel. However, the sub-panel also serves 3-phase equipment. When these 3-phase loads draw unbalanced currents, it can cause the neutral wire to carry current, creating a voltage drop between the neutral and ground.

Impact on Electronic Devices

Electronic devices can be sensitive to ground loop voltage. The scanner you're using may interpret this voltage as noise or interference, which can disrupt its operation.

Fix: Isolation Transformer

An isolation transformer can be a solution for ground loop voltage. It isolates the secondary circuit (your scanner) from the primary circuit (the branch circuit from the sub-panel).

How it Works

An isolation transformer has two separate windings: the primary winding is connected to the branch circuit, and the secondary winding is connected to the scanner. The magnetic coupling between the two windings transfers power from the primary to the secondary, but it also blocks any ground loop voltage.

Installation

To install an isolation transformer, connect the primary winding to the branch circuit and the secondary winding to the scanner. Make sure you follow the manufacturer's instructions carefully.

Benefits:

An isolation transformer offers several benefits: Eliminates ground loop voltage Improves electronic device performance* Provides additional isolation between the scanner and the power source Flag for review