Dictionary / Coil & Geometry
Ring/Center Ratio
Coil & GeometryA numeric ratio comparing the peak field strength of a coil to the field strength at the center. A ratio of at least 1.15 combined with a peak sitting at least 20% off-center indicates a Donut Coil, meaning the ring is meaningfully stronger than the center. A ratio near 1.0 with a centered peak indicates a Pancake Coil, meaning the center dominates. The ring zone location varies with coil size and is determined by where the windings are concentrated rather than a fixed distance.