Magnetic Flow Transducers
Magnetic flow transducers are based on Faraday‚s law of induced voltage:
e = Blv x 10-8
where e is the induced voltage in volts, B is the flux density in gauss, l is the length of the conductor in cm and v is the velocity of the conductor in cm/s. A flowing medium or fluid passing through a vessel is subjected to a transverse magnetic flux. (Figure 25) The fluid motion relative to the magnetic field induces a voltage which is proportional to the fluid velocity. An alternating or direct magnetic flux can be used, however if signal amplification is involved an alternating field is generally used.
Figure 25 Schematic of a magnetic flowmeter
Two basic types of magnetic flowmeters have been developed: one for highly conductive fluids and vessels and the other for slightly conductive fluids and non conducting vessels. For biomedical applications the second type of transducer is more applicable.
Some sources for possible error include circulating currents across the section of the vessel, conductivity of the vessel walls, fluid inhomogenity and non-uniform or non-axisymmetric flows.
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Support for the development of this module was provided by the National Science Foundation and The Cooper Union for the Advancement of Science and Art.
Please send questions or comments to Professor Ron Adrezin or Professor Daniel Raichel.