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

Abstract

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