Influence of the wire length on the of coil-less fluxgate properties of amorphous (Co0.94Fe0.06)72.5Si12.5B15 wire

In this study, the coil-less fluxgate (CF) properties of amorphous (Co0.94Fe0.06)72.5Si12.5B15 wire, current-annealed at 450 mA dc for 15 min under 500 MPa tensile stress and 16.5π rad/m torsional strain, have been investigated. A CF is a new type of magnetic-field sensor without a coil. The dependence of the second harmonic of the output voltage from the wire ends, Uwire, on an external magnetic field in the longitudinal direction, Hz, for the frequency range 5–50 kHz and various values of the ac current Iwire is presented. The results show that the sensitivity of the CF depends on the frequency and Iwire. Even at a very low frequency (5 kHz), a pronounced variation in the behaviour of the CF sensor is observed. A 60-mm long sensor has a maximum sensitivity of 78.5 V/T in a ±400 A/m linear operating range at 57 mA driving current. The sensitivity decreases but the linear operating range increases with decreasing wire length. A miniaturized 2.2-mm CF sensor shows ∼0.4 V/T sensitivity in a ±3000 A/m linear operating range at 53 mA driving current and 50 kHz ac driving-current frequency.