SENSOR FOR MAGNETIC FINE PARTICLE

摘要

A simple sensor capable of sensing magnetic fine particles at low cost with high accuracy and high rate while reducing noise source caused by a coil. The sensor comprises a Hall element (1) arranged on the XY plane and employing Hall effect. The Hall element is driven by a DC power supply (2). Under a state where an AC magnetic field is applied onto the Hall element in the direction of X-axis, a DC magnetic field is applied onto the Hall element in the direction of Z-axis by a permanent magnet (3). Varying magnetization of the Z component of magnetic fine particles is sensed by a lock-in amplifier (7). The AC magnetic field in the direction of X-axis may be generated by a coil (4) and an AC power supply (5) by a permanent magnet (10) and a motor (11), or by an AC power supply (21) and a conductor (22).