Patent ID: 6759601
Filing Date: 2004-07-06
Classification: G01G,G01N

Abstract:
An apparatus for determining an on-line measure of the mass of each of a plurality of discrete samples in a production line, the apparatus comprising:a transporter operable to transport said plurality of discrete samples along a transport path through an interrogation zone; a static magnetic field generator operable to generate a static magnetic field in a first direction through said interrogation zone for creating a net magnetisation within a current sample located within the interrogation zone; an alternating magnetic field generator operable to apply a pulse of alternating magnetic field in a second different direction through the interrogation zone for temporarily changing the net magnetisation of the current sample located within the interrogation zone; a position sensor operable to sense the position of each discrete sample on said transporter as it approaches the interrogation zone and operable to output a corresponding position signal; a controller operable to control the timing of the application of said pulse of alternating magnetic field by said alternating magnetic field generator in dependence upon the position 'signal output by said position sensor so that said pulse of alternating magnetic field is applied when said current sample is in the interrogation zone; a sensor operable to sense energy emitted by the current sample as the net magnetisation of the current sample returns to its original state and operable to output a sensor signal in dependence thereon; processing circuitry operable to process said sensor signal to determine a measure of the amplitude of the energy emitted by the current sample; a memory operable to store predetermined calibration data defining a relationship between said amplitude measure and mass, which calibration data is obtained from an amplitude measure determined by said processing circuitry for one or more similar samples of known mass; a determining device operable to determine said measure of the mass of the current sample using said calibration data and the amplitude measure output by said processing circuitry for the current sample; and wherein said static magnetic field generator is operable to generate a static magnetic field which is substantially homogeneous over a length of the transport path so that each sample is exposed to the static magnetic field for a predetermined period of time before it reaches the interrogation zone.