| 摘要 |
A flexible fluxgate sensor may comprise at least two flexible cores 1, 2 at least two sets of electrically conductive windings 5, 6 with at least one of the sets of windings being formed around each of the said cores and a flexible electrically conductive shield 7 enclosing the said cores 1, 2 and windings 5, 6. The cores 1, 2 may be sheathed in loose fitting and electrically insulating flexible tubes 3, 4. Alternative fluxgate sensors disclosed comprise open loop arrangements or have a length greater or equal to 0.5 metres or a fluxgate sensor with much the same features as that already disclosed above, which may or may not be flexible. Alternating current may be supplied to the windings and sensing means arranged to detect a voltage between the shield 7 and one of the sets of windings 5, 6. Alternating current (possibly pulses) and direct current may be supplied to the sensor via a transformer. The shield 7 and windings 5, 6 may be connected together, possible via short circuit or impedance elements, at a first end 15 of the sensor whilst the excitation signals and voltage sensing is performed at a second end 16 of the sensor. One or more sensors may be used to form a sensor several hundred metres long which may be arranged around a perimeter of a zone to be monitored and used in an access control system. |
