| 摘要 |
An alternating current field measurement (ACFM) probe comprises an inducer arrangement 102 for generating a magnetic field for inducing an alternating current field in a conductor 104, a sensor element 106 to produce a signal responsive to the alternating current field and a compensator element 108 to compensate for an influence of the generated magnetic field in the signal responsive to the alternating current field. The sensitivity of the probe to the distance of the probe from the surface i.e. lift-off is reduced. The sensor and compensator element may be coils, Hall effect sensors or giant magneto-resistive sensors. The inducer 102 may be trapezoidal. The sensor 106 and compensating element 108 may be electrically connected in reverse polarity, or alternatively circuitry comprising a differential amplifier may be provided, to subtract the output of the compensator element from the sensor to provide a compensated output. The probe may contain plural sensors and plural compensator elements. |
