Electromagnetic flow sensor

A method comprising metering a flow of fluid through a flow tube of an electromagnetic flow sensor;

• wherein the electromagnetic flow sensor is powered by a battery and comprises:
• a flow tube extending along a first axis and through which a fluid is able to flow;
• first and second electrodes spaced apart along a second axis transverse to the first axis to span a measurement volume within the flow tube;
• a magnetic circuit comprising a coil, one or more regions of remanent magnetic material and a gap defined between first and second parallel pole faces, wherein the flow tube is received within the gap such that magnetic field about the magnetic circuit is directed across the measurement volume parallel to a third axis transverse to the first and second axes;
• wherein the magnetic circuit is shaped to enhance uniformity of magnetic field within at least a central portion of the measurement volume such that along a line connecting respective centers of the first and second electrodes across the measurement volume, within a portion of the line within the central portion, a minimum magnetic field is greater than or equal to 70% or more of a maximum magnetic field, wherein the central portion corresponds to 90% or more of a width of the measurement volume parallel to the second axis.