Impedance of Helmholtz Coil to Generate Standard AC Magnetic Field in High Frequency

National metrology institute of Japan is developing AC magnetic field standard to calibrate AC magnetometers in high frequency bands. The demands for calibrations of the AC magnetometers in high frequency are increasing as electromagnetic field in several tens and hundreds kHz is used for some applications in these days. We designed and built several Helmholtz coils which has different diameters and wires. In this paper, the impedances of those Helmholtz coils are measured, and comparisons are performed. It is expected that these results are useful to choose a suitable size of Helmholtz coil at a target frequency and magnetic field level. The highest frequency is up to 500 kHz.