Patent ID: 6912904
Filing Date: 2005-07-05
Classification: E21B,G01F,G01H,G01N

Abstract:
1. An instrument comprising: exactly one tube that receives a sample fluid having a density; a rigid pressure housing enclosing said tube and forming an annular area between said tube and said pressure housing; a vibration source attached to said tube; exactly one vibration detector attached to said tube; and a measurement module electrically coupled to said vibration source and said vibration detector, wherein the measurement module is configured to determine a density of the sample fluid using a resonant frequency of the tube, wherein said vibration detector comprises: a first magnet mounted to said tube wherein said first magnet has a first magnetic field; a second magnet mounted to said first magnet wherein said second magnet has a second magnetic field that opposes the first magnetic field; a first coil winding mounted to said pressure housing; and a second coil winding mounted to said pressure housing adjacent to said first coil.