According to Faraday"s law of electromagnetic induction, when the conductor in a magnetic field moves in such way that cutting the magnetic lines the two ends of the conductor will induce electric potential e whose direction is determined according to the right-hand law and strength is proportional to
Magnetic induction intensity B,
the length of conductor in the magnetic field L and the moving speed of conductor u. If B £¬ L and u are vertical to
each other, e£½Blu.
In a magnetic field B where the magnetic induction intensity is uniform put a non-magnetic pipe whose diameter is D in vertical direction. When conductive liquid in the pipeline flows at speed u, it¡¯s cutting the magnetic lines. We can set a pair of electrodes in both ends of the pipe¡¯s Cross section. When the fluids in the pipe is flowing as axisymmetric distribution the electric potential will also be induced between electrodes£º e£½BD
The Volume flow qv is linear to electric potential e and diameter D meanwhile is inverse to the magnetic induction intensity B (not influenced by other physical parameters). It¡¯s the principle of Electromagnetic Flow meter.
special notes (it¡¯s essential to follow these measuring conditions)£º
¢ÙThe magnetic field is uniform and constant £»
¢ÚThe fluid is axisymmetric£»
¢ÛThe fluid is non-magnetic £»
¢ÜConductivity of the fluid is uniform and isotropic. |
