Electromagnetic detection system for variable area flowmeter
AssigneeRosemount Inc.
InventorPaul J. B. Nijdam
Life of this patent
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Abstract
A variable area flowmeter employing a vertical tube containing a displaceable magnet and a closed-loop magnetic detection circuit. The closed-loop magnetic detection circuit includes first and second magnetic cores each having a sense coil and a compensation coil. The sense coil provides an output related to magnetic field strength. With a feedback technique, the compensation coil compensates for the magnetic field through the sense coil. Field strength is determined by monitoring feedback. Displacement of the displaceable magnet is determined using information from the first and second magnetic cores. The detection circuit produces an output proportional to the position of the magnet within the tube. This output is translated into fluid flow.
Claims12
A flowmeter for measuring flow of a fluid through a flow passage, comprising:
- a displaceable magnet mounted within the flow passage responsive to fluid flow through the flow passage;
- sense means proximate the displaceable magnet for detecting a magnetic field emitted by the displaceable magnet and providing a field strength output related to field strength of the magnetic field;
- compensation means responsive to an input signal for producing a compensating magnetic field proximate the sense means;
- means for applying the input signal to the compensation means based upon the field strength output, whereby a feedback loop is created through the sense means and the compensation means carrying a feedback signal related to displacement of the displaceable magnet;
- and
- output means for producing an output related to fluid flow based upon the feedback signal.
A flowmeter for measuring flow of a fluid through a flow passage, comprising:
- a displaceable magnet mounted within the flow passage responsive to fluid flow through the flow passage;
- first detection means for providing a first electrical output signal related to displacement of the displaceable magnet;
- second detection means for providing a second electrical output signal related to displacement of the displaceable magnet;
- and
- means coupled to the first and second detection means for canceling effects of field strength variations and for providing an output related to fluid flow based upon displacement of the displacement magnet based upon the first output from the first detection circuit and the second electrical output signal from the second detection circuit.
Dependencies are inferred from the claim text.