P10.5 - Effect of Electrical Conductive Property on Electromagnetic Flow Meter

AMA Conferences 2015
2015-05-19 - 2015-05-21
Nürnberg, Germany
Proceedings SENSOR 2015
P10 - Applications
X. Zhang - Tsinghua University, Beijing (China)
884 - 887


An electromagnetic flow meter follows Faraday Induction Law. Apart from magnetic field, boundary condition of electrical conductivity is important in picking up the resulting signal. In use of the flow meter, the electrical conductive property of the flow meter may change because of electrode contamination. On the other hand, design of short measuring tube at the cost of losing some inductive voltage is a tendency to make the meter compact. To study these problems, electrodes and measuring tube of the flow meter were modified by insulating painting oil or by aluminum foil. By painting a portion of electrode surface, electrical resistance between two electrodes increased. To simulate a shorter measuring tube, aluminum foil was used to cover part of the inner wall of the tube. A shorter measuring tube would result a reduced inductive voltage in reading. The flow meter with different modifications was tested in a water flow calibration rig for its readings. Variations of readings were calculated and analyzed. In the experiment, it showed that change of electrical conductive property in electrodes caused serious reading errors, while the errors by the change in the meter’s tube length seemed to be less. Maximum error in 5 group data of electrode property change was 25%, compared to 10% of the tube length change in 9 group data. According to the theory of electromagnetic flow meter, flow at different position in the measuring tube has different contribution to the signal. This is described by the concept of virtual current. Virtual current is in turn determined by electrical boundary condition of the measuring tube as well as electrodes. Any change of these conditions would finally affect the reading of the flow meter. Further, asymmetry of the boundary value also causes error in the reading. The work offered experimental verification for the theory and could help to a better design of the flow meter.