A reduced-cost apparatus for calibrating the sensitivity and orthogonality of a triaxial magnetometer, and a method for adjusting the distance between the two coils of a Helmholtz coil and other related parameters are described herein. A method can include positioning a calibrated magnetometer within a mounting fixture between two coils of a Helmholtz coil, the two coils arranged in mutually parallel planes and separated by the radius of the Helmholtz coil, the mounting fixture mounted such that a position of the mounting fixture is adjustable along an axis orthogonal to the mutually parallel planes; adjusting the position of the mounting fixture over at least some of the positions and measuring the magnetic field at each position to generate a set of magnetic field measurements associated with the positions; and adjusting the first distance based on the first set of magnetic field measurements. Additional apparatuses, systems, and methods are disclosed.