Low-Power Electromagnetic Flowmeter.

摘要

A system for minimizing the power requirement of a flowmeter intended for long-term unattended deployment in a current flowing through a body of conductive fluid. The system includes a pair of electrodes in contact with the fluid, and a permanent magnet which generates a magnetic field which is orthogonal to a line passing between the electrodes. An electromagnetic coil is also provided, and is selectively activated and deactivated to establish the orthogonal magnetic field at a first level during first time periods in a series of first time periods, and at a second level during second time periods in a series of second time periods. The ratio of the time duration of a first time period to a second time period is substantially less than one. Means coupled to the electrodes generate a first signal during a first time period and a second time signal during a second time period, the first and second signals together enabling determination of an error term, comprising the potential difference between the electrodes when the electrodes are in contact with the fluid, and there is no magnetic field proximate to the electrodes. (Author)