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Causes of errors in electromagnetic flowmeters

by:Sure     2020-06-29
Electromagnetic flowmeter YK-LDG-S error when measuring medium is mainly due to the following three factors: flowmeter selection problem, external interference, media problems; 1. Problem of flowmeter selection 1. Medium flow rate Electromagnetic flowmeter YK-LDG-S can measure the flow rate range is generally ~ 10m/s, economic flow rate range is ~ 3m/s. When using it, the inner diameter of the measuring tube should be selected according to the size of the medium flow and the measurable range of the flowmeter. 2. Problems with lining and electrode materials The lining and electrode materials are in direct contact with the medium. The electrode and lining material should be selected according to the characteristics of the medium (whether it is corrosive) and the operating temperature. If the selection is not suitable, it will cause measurement errors. 3. Measurement of mixed fluids When using the electromagnetic flowmeter YK-LDG-S to measure the flow rate of liquid and solid mixed fluids (such as water containing sediment), if an electromagnetic flowmeter calibrated from a single-phase liquid is used, a measurement error will occur. Select the sensor installed at the straight pipe section that will not cause liquid-solid separation. 4. The problem of excitation stability There are three main excitation methods for electromagnetic flowmeters: DC excitation, AC sine wave excitation and dual-frequency rectangular wave excitation. Dual-frequency rectangular wave excitation has both low-frequency rectangular wave excitation excellent zero-point stability and high-frequency rectangular wave excitation pairs. The fluid noise is strong enough to suppress the ability, which is the ideal way of excitation. In practical application, the stability of the power supply voltage and frequency should be ensured as much as possible to ensure the constant magnetic field strength and reduce the measurement error caused by the change of the magnetic field strength. 2. Outside interference 1. Space electromagnetic interference The cable between the converter and the sensor is relatively long. In a relatively strong electromagnetic environment, it is very susceptible to interference, which causes the measurement value of the instrument to appear, which is difficult to display normally. 2. Problems with connecting cables The essence of the application of the flowmeter is that a specific cable is used to connect the converter to the sensor to form a complete system, so the cross-sectional area, capacitance, and cable site will have an impact. 3. The problem of grounding Because the output signal of the sensor is small, basically only a few millivolts, in order to improve the anti-interference ability, the zero potential of the sensor must be grounded separately, and the ground point of the sensor output signal should be electrically connected to the medium. 4. Vibration of the mounting point of the symmetrical point of the electrode and excitation coil The excitation coil and electrode of the electromagnetic flowmeter YK-LDG-S need to be symmetrical. Once asymmetric, the deviation in the production process will be caused, and the measurement result is difficult to ensure accurate conditions. In addition, the installation site must meet a relatively high anti-vibration standard, otherwise the accuracy of the measurement cannot be guaranteed, and even the instrument may not work properly. Third, the media problem 1. Dielectric conductivity changes drastically When the conductivity is large, it will cause a large fluctuation of the value. If it is very serious, it will be difficult to achieve normal work; and when the conductivity is too low, the electrode will have difficulty in normal output. If the conductivity is below the lower limit during operation Range, then the flowmeter is difficult to work properly. 2. The medium has bubbles or partial tubes The bubbles mainly come from the bubbles dissolved in the liquid and developed into a free state and the bubbles sucked from the outside. A flow containing a large volume of bubbles will affect the accuracy of the measurement. If the bubble diameter is too large, or even exceeds the value of the electrode diameter, an unstable state will appear during the measurement display process, and fluctuations cannot be avoided. 3. The medium is asymmetric In the measurement, the medium is asymmetrical, and there are two main combinations: one is a single vortex flow; the other is a linear flow along the axis of the pipeline, and the volume flow of the liquid is the integral of the pipe cross section. 4. There is a layer in the tube Electromagnetic flowmeter YK-LDG-S is used to measure fluid. The non-clean fluid contains some impurities such as precipitates, which makes the surface of the electromagnetic flowmeter YK-LDG-S electrode or the pipeline contaminated, resulting in an error in the measurement results.
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