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

In this study, the coil-less fluxgate (CF) properties of amorphous (Co0.94Fe0.06)(72.5)Si12.5B15 wire, current-annealed at 450 mA dc for 15 min under 500 MPa tensile stress and 16.57 pi 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, U-wire, on an external magnetic field in the longitudinal direction, H-z, for the frequency range 5-50 kHz and various values of the ac current I-wire is presented. The results show that the sensitivity of the CF depends on the frequency and I-wire. 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 78.5V/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 similar to 0.4V/T sensitivity in a +/- 3000A/m linear operating range at 53 mA driving current and 50 kHz ac driving-current frequency. (C) 2010 Elsevier B.V. All rights reserved.