glass vials are useful as the container because they do not give a signal that might interfere with the measurement process in this embodiment check weighing station 24 includes a permanent magnet 34 rf probe 35 shown diagrammatically in fig1 and a computer control system 36 having a processor 38 magnet 34 creates a homogeneous direct current dc or static magnetic field in the x direction across conveyor belt 28 in a region that may be referred to as the interrogation zone 40 interrogation zone 40 extends the length of conveyor belt 28 through which the static magnetic field is uniformly applied by permanent magnet 34 the sample in vial 22 contains nuclei which each possess a magnetic moment e g 1h nuclei protons as a result of the spin of the nuclei because the sample protons posses a magnetic moment the sample is capable of acquiring a net magnetisation when under the influence of certain magnetic fields when the sample is within interrogation zone 40 the applied static magnetic field creates a net magnetisation within the sample a vial position detection device 42 preceding or at the start of interrogation zone 40 such as the optical position sensor 44 having a light beam 46 accurately and precisely detects when vial 22 reaches a known physical position on conveyor belt 28 preceding check weighing station 24 in most nmr systems the static magnetic field strength is such that the larmor frequency of the sample is in the radio frequency range of the electromagnetic spectrum applying an alternating current ac magnetic field to the sample at the sample 39 s larmor frequency and orientated.