Design and construction of a single-axis, low-frequency magnetic probe (B-dot probe) calibrated with a LC_var Helmholtz resonant circuit

Magnetic probes (also known as B-dot coil) are electromagnetic devices used to measure magnetic field variations in many frequency ranges. The measured magnetic field frequency directly relates to the elected method to make the B-dot coil calibration. This work presents a B-dot coil calibration in a frequency range from 6.16 kHz to 36.63 kHz. An inductor L (Helmholtz coil) connects in parallel with a variable capacitor bank Cvar to form a coupled LCvar resonant circuit. The LCvar circuit is fed with a half bridge oscillator. The capacitance Cvar is varied until the circuit is in a resonant state at different frequencies. The resonant circuit produces sinusoidal oscillations in the aforementioned frequency band. The sensitivity is calculated by using voltage Vout of the B-dot coil and voltage VH measured from Helmholtz terminals.