US Patent 7628080 Magnetic flow meter providing quasi-annular flow

An in-line magnetic flow meter has an electrically insulated quasi-annular voltage sensing path defined between an internal wall of a meter body and an outer wall of an axially disposed hollow tube. Although less than 100% of the fluid flow passes through the sensing region, the choice of an inner tube reduces flow impedance introduced by the meter, when compared to other meters providing a quasi-annular sensing path. In addition, by forming two electromagnet coils on a single core and using axially separated pairs of electrodes, the present arrangement allows one to provide two flow meters in the space normally occupied by one.