Is it farther or further?
An instrument for measuring the magnitude and direction of a magnetic field. Magnetometers are often used in archaeological and geological investigations to determine the intensity and direction of the Earth's magnetic field at various times in the past by examining the strength and direction of magnetization of ferromagnetic materials in different geological strata. See also magnetic reversal.
instrument for measuring the strength and sometimes the direction of magnetic fields, including those on or near the Earth and in space. Magnetometers are also used to calibrate electromagnets and permanent magnets and to determine the magnetization of materials