A pair of identical loop coils placed parallel to each other and separated by a distance equal to their radius, designed to create a highly uniform magnetic field in the space between them. This uniform coverage is useful when consistent field strength across a target area matters more than peak intensity at a single point. Unlike a butterfly loop coil where the two loops angle inward to focus the field, a Helmholtz pair keeps the loops parallel so the fields overlap evenly.
Some accessories use a pair of loops. A butterfly coil angles two loops inward toward each other so their fields add up over one focused spot. A Helmholtz pair holds two matching loops parallel and about a radius apart, which makes the field in the space between them unusually even.
