What is galvanic isolation?

• A. A method to shield devices from magnetic interference.
• B. Electrical isolation between circuits so no direct DC path exists between them.
• C. A technique for converting AC signals to DC.
• D. A circuit that automatically reconfigures loops.

Answer: (B)

Galvanic isolation means two circuits are electrically separated so there is no direct current path between them. Signals cross the barrier without a conductive link, using non‑conductive coupling methods such as opto-isolators or transformers. In a 4–20 mA loop with HART, this keeps the field device and the control/monitoring side electrically separate, so a fault, ground difference, or surge on one side can’t drive current into the other. The current loop on each side can still carry its signal, while the barrier preserves safety and protects equipment by preventing direct electrical connections. This isn’t about shielding from magnetic interference, converting AC to DC, or automatically reconfiguring loops.