The electromagnetic flowmeter is developed based on Ferrari's electromagnetic induction principle, so its advantages have been effectively inherited. However, the disadvantage is that it is susceptible to external electromagnetic interference. If these external factors are not effectively handled during installation, the electromagnetic flowmeter is prone to measurement errors.
Below we summarize five main factors that affect the error of electromagnetic flow meters
1. Measure the liquid filling inside the pipeline
The main reason for this phenomenon is due to insufficient back pressure in the pipeline or poor installation of flow meter sensors, resulting in the pipeline not being fully filled. The corresponding faults will also have different manifestations depending on the degree of not being fully filled
① When a small amount of gas is distributed in a layered or wavy flow in the pipeline, there may be discrepancies between the measurement results and the actual results;
② When the fluid is a bubble flow or plug flow, in addition to the measurement results not matching the actual situation, it can also cause fluctuations in the measurement data of the instrument due to the instantaneous coverage of the electrode surface when the bubbles flow through the instrument sensor;
③ When the cross-sectional area of fluid flow in the pipeline increases, it indicates that the liquid is not fully filled in the pipeline, and there will also be fluctuations in the measurement data of the instrument;
④ When the pipeline is not fully filled, to the point where the liquid level is below the electrode of the flowmeter, the instrument will experience overfilling. This type of malfunction is mainly caused by users' inaccurate estimation of their own flow range during selection;
2. Measuring the presence of solids in liquids
When measuring liquids containing solids such as powders, particles, or other fibers, the following faults are generally manifested
① The flow meter inside the pipeline produces noise;
② Surface contamination of electrodes;
③ The conductive or insulating deposition layer inside the pipeline covers the electrode surface or lining;
④ The lining of the instrument is worn or deposited, resulting in an increase or decrease in the cross-sectional area of fluid flow;
3. Liquid that is prone to crystallization
Some liquids that are prone to crystallization can be measured using electromagnetic flow meters at normal temperatures, but this requires good heat tracing in the pipeline. However, in most cases, it is difficult for the measuring tube of the electromagnetic flow meter sensor to maintain a constant temperature once the temperature drops. The liquid will crystallize and cover the surface of the pipeline, causing instrument failure
4. Improper selection of grounding ring material for electromagnetic flowmeter
5. The conductivity of the liquid does not meet the requirements
Due to the working principle of the electromagnetic flowmeter being based on the Ferrari electromagnetic induction principle, there is a certain requirement for the conductivity of the liquid being measured to be ≥ 5 μ s/cm. When the conductivity of the liquid is below this lower limit, it can also cause fluctuations in the measurement data of the instrument.