Theory of induced voltage electromagnetic flowmeasurement

The contribution of each part of the flow to a meter signal is expressed in terms of a weight vector
W
and the velocity ν, with the signal
\propto \int \nu \cdot W dr
over the flowmeter volume.
W
depends on the magnetic field
B
and a vector defined entirely by the electrode and flowmeter geometry. A meter is called "ideal" if the signal is proportional to the flow rate and independent of the flow pattern. The condition on
W
for this is given and an experimental ideal meter mentioned. Since meters with small (point) electrodes cannot be ideal, weaker conditions on
W
for flows of different types are reviewed. A technique for designing short meters suitable for rectilinear flow with an unknown axisymmetric velocity profile is briefly described. The behavior of different shapes of electrodes, including electrodes of finite and variable conductivity, is discussed. Finally the problems of pulsating flow, magnetic field specification, and nonuniform and anisotropic blood conductivity are discussed.