Magnetic flowmeter with power limit and over-current detection
AssigneeRosemount Inc.
InventorsScot Ronald Foss, Jared James Dreier, Samuel Ethan Messenger, Kirk Allan Hunter
Life of this patent
Estimating the term…
Abstract
A magnetic flowmeter includes circuitry for sensing coil current, coil voltage, or coil resistance. Based on the sensed coil current, voltage, or resistance, a digital processor determines whether a power limit or a coil current limit is exceeded and either halts operation until it receives a new configuration with a new coil current setpoint, or determines a new coil current setpoint itself and adjusts the magnetic flowmeter to that new coil current setpoint.
Claims24
A method of controlling operation of a magnetic flowmeter, the method comprising:
- supplying a current from a coil driver to a coil of the magnetic flowmeter;
- measuring coil resistance;
- determining coil power based on a coil current value and measured coil resistance;
- and
- controlling the coil driver based upon the coil power determined and a coil power limit value.
A method of controlling operation of a magnetic flowmeter, the method comprising:
- supplying current at a coil current setpoint level to a coil of a magnetic flowmeter;
- sensing a voltage induced between sensing electrodes by a magnetic field produced by current flow in the coils;
- producing a flow value based on the voltage induced between the sensing electrodes;
- sensing coil current;
- sensing coil voltage;
- calculating coil resistance based on the sensed coil current and the sensed coil voltage;
- calculating coil power using the coil resistance and a coil current setpoint;
- and
- discontinuing supplying current to the coil if the calculated coil power exceeds a power limit level for a time period.
A method of controlling operation of a magnetic flowmeter, the method comprising:
- supplying coil current to a coil of a magnetic flowmeter;
- sensing coil current and coil voltage;
- calculating coil resistance based on the sensed coil current and sensed coil voltage;
- calculating coil power based on coil resistance and a coil current setpoint;
- and
- inhibiting normal operation of the magnetic flowmeter if the calculated coil power exceeds a power limit value.
A method of controlling operation of a magnetic flowmeter, the method comprising:
- measuring resistance of a coil of a magnetic flowmeter;
- calculating coil power based on the resistance of the coil and a coil current setpoint;
- and
- inhibiting normal operation of the magnetic flowmeter if the coil power exceeds a power limit.
A method of controlling operation of a magnetic flowmeter, the method comprising:
- supplying coil current at a test current setpoint and a test frequency setpoint to a coil of a magnetic flowmeter for a test period following startup of the magnetic flowmeter;
- sensing coil voltage and coil current during the test period;
- determining coil power during the test period based on the sensed coil voltage and sensed coil current;
- selecting a normal coil current setpoint and normal frequency setpoint for normal operation of the magnetic flowmeter based on the coil power during the test period.
A transmitter for use with a magnetic flowtube, the transmitter comprising:
- a coil driver for supplying a current to a coil of the magnetic tube, the coil driver including circuitry for sensing coil current and coil voltage;
- and
- a processor for determining coil power based on sensed coil current and sensed coil voltage, and controlling the coil driver based upon the coil power determined and a coil power limit value.
A method of controlling operation of a magnetic flowmeter, the method comprising:
- supplying coil current to a coil of a magnetic flowmeter;
- sensing the coil current;
- and
- inhibiting normal operation of the magnetic flowmeter if the coil current exceeds a current limit for a test period.
A magnetic flowmeter comprising:
- a flowtube having a coil for producing an alternating magnetic field and electrodes for sensing voltage induced by the magnetic field in fluid flow through the tube;
- a coil driver connected to the coil to produce the alternating magnetic field at a coil drive frequency and at a current setpoint, the coil driver including circuitry for sensing coil current;
- and
- a processor that generates a flow output as a function of a sensed voltage between the electrodes, wherein the processor controls the coil driver based on a comparison of the sensed coil current and a coil current limit.
Dependencies are inferred from the claim text.