Abstract
Using a FeCoSiB amorphous wire and a coil wrapped around it, we have developed a sensitive magnetic sensor. When a 5 mm long amorphous wire with the diameter of 0.1 mm was used, the magnetic field noise spectrum of the sensor was about 30 pT/√Hz above 30 Hz. To show the sensitivity and the spatial resolution, the magnetic field of a thousand Japanese yen was scanned with the magnetic sensor.
Highlights
Many kinds of high sensitive magnetic field sensors have been developed
A fluxgate magnetometer can measure the DC magnetic field [3]. It consists of three coils wound around a ferromagnetic core: an AC excitation winding, a detection winding that indicates the zero field condition and a DC bias coil that creates and maintains the zero field
When a proper DC bias field is applied to the sensor, due to the nonlinearity of the B-H curve of the amorphous wire, the amplitude of the AC voltage VAC
Summary
Many kinds of high sensitive magnetic field sensors have been developed. Among them, the inductive coil sensor [1] is one of the most commonly used magnetic types. Inductive coil sensors cannot measure the DC magnetic field and it is difficult to obtain low noise levels at low frequency with small inductive coil sensors. Giant magnetoresistive (GMR) sensors [5], anisotropic magneto resistive (AMR) sensors [6], and magneto-impedance (MI) sensors [7,8] can measure DC magnetic fields and have big measuring bandwidth. They have been developed and used in various areas like nondestructive evaluation, communication, geological exploration, medical diagnostics, security control, etc. We will describe a small simple sensitive magnetic field sensor using (Fe0.06Co0.94)72.5Si2.5B15 (FeCoSiB) amorphous wire with a coil wrapped around it
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