Abstract: An apparatus for measuring the magnetic field distribution of a magnetic sample includes a magnetic field sensor arrangement having three, orthogonally-disposed, Hall sensors for sensing the magnetic field produced by a magnetic sample at a given location, The sensor arrangement is scanned along a predetermined scan pattern. The apparatus then acquires sampling data from the sensor arrangement, the sampled data providing a representation of the magnetic field distribution of the magnetic sample. The data is preferably acquired by an interface card for a PC, which stores sampled data in the main memory of the PC for data analysis and display.

Abstract: A tamper proof closure (1) has a plurality of magnetic strips (7) attached thereto which are arranged to be broken if the closure is opened. The broken magnetic strips have a different magnetic characteristic as compared to when they are intact and this can be sensed with a Hall effect or other sensor. The tamper proof closure enables the condition of article closures such as the screw caps of liquor bottles to be remotely monitored.