パルス励磁アモルファスワイヤ磁気インピーダンス素子を用いたコイル検出型磁界センサのノイズ特性評価

概要

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In this experiment, we investigated noise characteristics of a pulse magneto-impedance sensor which is based on an amorphous magnetic wire with a pickup coil. For a helical static magnetization, the ac current i passing the wire induces a coil voltage Vc in the coil around the wire. The pulsed excitation, combining both high and low frequency harmonic, produces the voltage Vc with dc current biasing. We describe improvements of pulse excitation conditions for an amorphous magnetic wire to reduce magnetic noises. The relation between the time interval of a current pulse train T and magnetic noises was investigated. The magnetic noise is suppressed clearly when T is smaller than 1.5 μs for pulse width 10 ns. Under the optimal conditions, the rms noise of 1-cm-long an amorphous wire magneto-impedance sensor with 600 turns of the pickup was estimated as 1pT/Hz1/2M at 20 Hz∼500 Hz.