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What are the factors that affect the accuracy of the electromagnetic flowmeter?

The electromagnetic flowmeter is a meter that measures the flow rate according to Faraday's law of electromagnetic induction and is used to measure the volumetric flow of conductive liquid in the pipeline. The electromagnetic flowmeter is easy to install, horizontal, vertical and inclined; the measurement accuracy is high, it can reach 0.5%; the range ratio is large, generally 1:20. The liquid to be tested is only in contact with the pipe lining and the electrode of the electromagnetic flowmeter. Therefore, as long as the electrode and the lining material are properly selected, it has good corrosion resistance and wear resistance, and plays an extreme role in industrial production. There are some problems affecting the measurement accuracy during the measurement of the electromagnetic flowmeter. Users must pay attention to the following points:

1. Because the flow signal is small and susceptible to external disturbances, the disturbance source mainly has pipeline stray current, static electricity, electromagnetic wave and magnetic field. Do not share grounding with other motors and appliances. Signal lines between sensors and converters are introduced. Generally, shielded cables are used. Keep away from strong magnetic fields.

2. If the liquid to be tested contains metal, the electrode of the flowmeter is prone to short circuit, and the measured value of the flowmeter is obviously too small or tends to zero.

3. Since the electromagnetic flowmeter measures the suspension solid phase or the dirty body much more than other flow meters, the probability of failure of the inner wall adhesion layer is relatively high.

4. If the electrical conductivity of the adhesion layer is close to the liquid conductivity, the instrument can output the signal normally, but only change the flow area to form a hidden fault of the measurement error; if it is a high conductivity adhesion layer, the electromotive force between the electrodes will be short-circuited; if it is insulating The adhesion layer, the electrode surface is insulated and the measurement circuit is turned off. The latter two phenomena will make the meter inoperable.

5. The electrode and the lining material are directly in contact with the liquid to be tested. The electrode and the lining material should be selected according to the characteristics of the liquid to be tested (such as corrosiveness, abrasiveness, etc.) and the working temperature. If improperly selected, the adhesion speed and corrosion will be caused. Problems such as scaling, wear, and lining deformation, which in turn cause measurement errors, so it should be given high priority when selecting equipment.

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