Electromagnetic flowmeter with alternating permanent magnet field

Abstract

An electromagnetic flowmeter in which the fluid being metered is conducted through a flow tube having a pair of electrodes, the fluid intersecting a magnetic field whereby the resultant voltage induced in the fluid is transferred to the electrodes to provide a signal indicative to flow rate. The magnetic field is created by a pair of pole pieces formed of "hard" magnetic material. The pieces are placed at diametrically-opposed positions and are magnetically interconnected to define a magnetic circuit. Excitation pulses which alternate in polarity are periodically applied by respective magnet drivers to coils wound about the pole pieces to alternately magnetize the pieces in one direction and remagnetize the pieces in the reverse direction, thereby establishing the desired field. The duty cycle of the pulses is such as to reduce the average power requirements to a very low level. In order to operate the flowmeter from a standard 50 or 60 Hz power line, the line voltage is divided by an odd integer to permit the magnet drivers to be alternately triggered on the peak positive and peak negative crests of the power line voltage.

Dependencies are inferred from the claim text.