Torsion sensor based on the coil-less fluxgate effect

The torsion dependence of the coil-less fluxgate properties of amorphous (Co0.94Fe0.06)72.5Si12.5B15 wire was investigated. The results show that the second harmonic of the output voltage from the wire ends, Uwire, varied linearly at the ±30 π rad/m torsion range for as-cast wire and ±5 π rad/m torsion range for annealed wire. It was also found that if the sample was annealed at higher torsion, the curve shifted negatively or positively depending on the direction of torsion applied during the annealing. Most importantly, the output signal changed its sign as the direction of external torsion reversed, and therefore the proposed torsion sensor could detect whether torsion was in the negative or positive (clockwise or anti-clockwise) direction.