| Electromagnetic flowmeter, which is based on Faraday's induction law, is a velocity-type flowmeter, and is widely used nowadays. For the conventional electromagnetic flowmeter, there is a pair of electrodes installed on the electromagnetic flowmeter's sensor. However, great errors will be introduced due to the variation of cross sectional area of the flow when the pipe is not fully filled. What's worse, the conventional electromagnetic flowmeter can not work when the surface level of the flow is below the electrodes. To overcome these, a multi-electrode electromagnetic flowmeter is designed, which can be applied for the flow measurement of the partially filled pipes. The main research points and the innovation of the thesis are listed as follows:(1) The working principle, the development history and the characteristics of the electromagnetic flowmeter are introduced. And the characteristics of the partially filled flow are analysed as well as the currently existing electromagnetic flowmeters for this situation.(2) A novel multi-electrode electromagnetic flowmeter sensor for the partially filled pipes is proposed, which use three pairs of electrodes installed on the inner wall of the electromagnetic flowmeter's sensor at different heights. Moreover, a differential pressure sensor is to obtain the liquid level. Thus the electrodes below the current liquid level can be selected for the flow measurement.(3) The hardware design of the multi-electrode electromagnetic flowmeter based on the MSP430 microprocessor as well as the relative software design are given.(4) The initial research on the multi-electrode electromagnetic flowmeter is conducted. Experiments are done for the fully filled pipes and the partially filled pipes. Results show that there is a fine aid repeatable linear relationship between the output voltage of the three pairs of electrodes and the flow velocity, and that the proposed flowmeter can be used for flow measurement.
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