Model 6402 Helmholtz coil system has twin 0.6 metre (2ft) diameter coils in a Helmholtz configuration and normally used as a Magnetic Field Immunity Test System or simply a low frequency magnetic field calibrator. A magnetic field is produced by two coils that is essentially homogenous throughout the volume between the face of the coils and one-third diameter of the coils at it’s centre. The coils are supported by a non-metallic framework. A rotating, height-adjustable pedestal is capable of holding articles weighing up to 15kg. The Coil has been initially calibrated at the NPL in terms of uT/amp at 50Hz. For the end user’s convenience NPL have also quoted a figure of uTesla per millivolt as measured across an installed shunt resistor with measuring terminal placed at the base of the Helmholtz. This was done at 60Hz and 2kHz.