Back to results
US 4,932,268 AGranted
Electromagnetic flow measuring arrangement
AssigneeFlowtec AG
InventorPeter Hafner
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeFlowtec AG
InventorPeter Hafner
Estimating the term…
In an electromagnetic flow measuring arrangement an electrically conductive fluid flows through a measuring tube in which a magnetic field is generated transversely of the flow direction, whereby a voltage is induced which is proportional to the flow velocity. This voltage is tapped by means of two electrodes. The cavity of the measuring tube has an elliptical cross-section with two major axes, the first major axis coinciding with the connecting line of the two electrodes, and the second major axis coinciding with the direction of the magnetic field. The flow to be measured is proportional to the product of the measured flow velocity and the cross-section area of the cavity of the measuring tube. The flow measuring arrangement is constructed so that on changes of the cavity cross-section caused by external influences the cross-section retains substantially the profile of an ellipse and the length of the second major axis remains substantially constant. In this way external influences, such as pressure and temperature, that change the cross-section of the cavity of the measuring tube, do not affect the measuring result.
An electromagnetic flow measuring arrangement comprising a measuring tube of which the cavity in cross-section has the profile of an ellipse having a first and a second major axis and a first cross-sectional area, means for generating a magnetic field directed transversely of the flow direction, two electrodes arranged at points of the measuring tube opposite each other along the first major axis for tapping off an electrical voltage which is induced when the measuring tube is traversed by an electrically conductive medium and which is proportional to the flow through the measuring tube, and structural members supporting the measuring tube at points which lie opposite each other along the second major axis, said structural members having sufficient strength to keep the length of the second major axis constant when the cross-sectional area of the cavity of the measuring tube is changed by external influences, said measuring tube maintaining substantially an ellipse profile on such changes of said cross-sectional area so that changes in cross-sectional area will not change the proportionality between the induced voltage and the flow.
An electromagnetic flow measuring arrangement comprising a measuring tube of which the cavity in cross-section has the profile of an ellipse having a first and a second major axis, means for generating a magnetic field directed transversely of the flow direction, two electrodes arranged at points of the measuring tube opposite each other along the first major axis for tapping off the electrical voltage which is induced when the measuring tube is traversed by an electrically conductive medium, and structural members supporting the measuring tube at points which lie opposite each other along the second major axis, said structural members keeping the length of the second major axis constant when the cross-sectional area of the cavity of the measuring tube is changed by external influences, said measuring tube maintaining substantially an ellipse profile on such changes of such cross-sectional area, the structural members being formed from different materials having thermal coefficients of expansion which are adapted to each other in such a manner that the temperature-induced shape changes of the measuring tube do not lead to any change in length of the second major axis.
Dependencies are inferred from the claim text.