Magnetic flowmeter with coil ground path detection
AssigneeRosemount Inc.
InventorsScot R. Foss, Robert K. Schulz
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Abstract
A magnetic flow meter includes a flowtube arranged to receive a flow of process fluid and a coil proximate the flowtube arranged to apply a magnetic field to the process fluid. A sense electrode is arranged to sense a voltage potential in the flowtube in response to the applied magnetic field. The sensed voltage is indicative of flow rate of process fluid through the flowtube. Diagnostic circuitry provides an output related to an electrical path between the coil and electrical ground.
Claims22
A magnetic flow meter, comprising:
- a flowtube arranged to receive a flow of process fluid;
- a coil proximate the flowtube arranged to apply a magnetic field to the process fluid;
- a first electrical switch configured to selectively couple the coil to an electrical ground through a first electrical path;
- a second electrical switch configured to selectively couple the coil to the electrical ground through a second current path;
- a sense electrode arranged to sense a voltage potential in the flowtube in response to the applied magnetic field, the voltage potential indicative of flow rate of process fluid through the flowtube;
- and
- diagnostic circuitry having an output indicative of a current through an electrical leakage path between the coil and electrical ground.
A method for measuring electrical resistance between a coil of a magnetic flow meter and electrical ground, comprising:
- applying an alternating current to the coil proximate a fluid flow;
- sensing a voltage in the process fluid and responsively determining fluid flow;
- measuring coil to ground leakage resistance in accordance with the steps of:
- providing an electrical path between the coil to the current source;
- opening any current return path of the coil to the current source;
- and
- measuring current flowing through the coil indicative of current flowing to electrical ground through the leakage resistance.
Dependencies are inferred from the claim text.