Method for magnetic field tracking in a NMR check weighing system

• US 20050242808A1
• Filed: 04/30/2004
• Published: 11/03/2005
• Est. Priority Date: 04/30/2004
• Status: Active Grant

• Current Assignee: Bruker Biospin GMBH (Bruker Corporation)
• Original Assignee: BOC Group Pty Limited (Linde Plc)
• Inventors: McKendry, James M., Corver, Jozef A. W. M., Selway, Robert
• Granted Patent: US 7,061,239 B2
• Time in Patent Office: Days
• US Class Current: 324/307
• CPC Class Codes: G01N 24/085 Analysis of materials for the purpose of controlling industrial production systems
• CPC Class Codes: G01R 33/389 Field stabilisation , e.g. by field measurements and control means or indirectly by current stabilisation

Abstract

A method (10) insures that the characteristics of the magnetic field used in a magnetic resonance check weighing system (20) for samples in vials (22) on a production line track deviations from the resonant frequency of the sample. The method (10) includes the steps of obtaining (50) a free induction decay signal from a magnetic resonance measurement of the sample, monitoring (52) from the free induction decay signal the deviation of the resonance frequency of the magnetic resonance measurement from a preselected resonance frequency; and adjusting (62) the magnetic field to maintain the preselected resonance frequency.

Claims

1. A method for use in a magnetic resonance check weighing system for samples on a production line, the magnetic resonance check weighing system having a magnetic field, comprising the steps of:

obtaining a free induction decay signal from a magnetic resonance measurement of the sample;

monitoring from the free induction decay signal, during check weighing of production samples, the deviation of the resonance frequency of the magnetic resonance measurement from a preselected resonance frequency; and

adjusting the magnetic field to maintain the preselected resonance frequency.

2. The method according to claim 1, wherein said step of monitoring includes the steps of extracting the resonance frequency from the free induction decay signal, and calculating the deviation of the resonance frequency of the magnetic resonance measurement from a preselected resonance frequency.

3. The method according to claim 2, wherein said step of extracting the resonance frequency includes the step of adjusting the resonance frequency value over a plurality of magnetic resonance measurements of the sample.

4. The method according to claim 1, wherein the magnetic resonance check weighing system includes a shim electromagnet for adjusting the magnetic field, and said step of adjusting the magnetic field includes the step of adjusting the shim electromagnet.

5. The method according to claim 4, wherein the step of adjusting the shim electromagnet includes the step of adjusting a value processed by a digital to analog converter controlling the magnetic field generated by the shim electromagnet.

6. The method according to claim 1, wherein the magnetic resonance check weighing system includes a plurality of magnets and other components, and said step of adjusting the magnetic field includes the step of adjusting the spatial orientation of one of the plurality of magnets and other components.

7. The method according to claim 1, wherein the magnetic field is operated by a device having an electrical signal gain, and said step of adjusting the magnetic field further includes the step of determining and removing the gain before said step of adjusting the magnetic field.