The necessary conditions for improving the accuracy of the electromagnetic flowmeter

1. Accurate Model Selection of Electromagnetic Flowmeter Firstly, it is necessary to realize a reasonable choice of the aperture of the electromagnetic flowmeter sensor: the choice of this index will have a decisive influence on the flow velocity of the fluid in the pipeline, and will also produce obvious influence on the output potential parameters. influences. Therefore, in the process of selecting the electromagnetic flowmeter, it is not necessary to use the diameter of the connecting process pipe as a selection index, but should be selected according to the actual use flow rate. Generally, in the case where the fluid flow velocity inside the pipe to be installed is in the range of 1.5 to 3.0 m/s, the diameter of the sensor needs to be consistent with the diameter of the pipe to be installed, and in the case where the fluid flow velocity inside the pipe is <0.5 m/s. , you need to control the gauge of the instrument below the pipe diameter.
Secondly, in order to adapt to the measurement conditions of different media, such as temperature, pressure, corrosion, wear and other requirements of the fluid medium, different linings and electrode materials should be used. If it is prone to wear resistance, it is recommended to choose a urethane rubber material. If it tends to have corrosion resistance, it tends to choose a PTFE material.
2. Reasonable installation of electromagnetic flowmeter Firstly, from the perspective of the requirements of the installation pipeline, the flow velocity distribution in the electrode plane state has begun to show a certain difference with the data at the initial calibration. In this process, the most important indicator of the particular flow velocity distribution is the level of configuration of the pipe connections upstream of the sensor. If there are problems and defects in the installation of the pipeline, the electromagnetic flowmeter may have a significant amount of displacement problem during its normal use. At the same time, from the point of view of practical engineering application, the installation of the straight pipe sections before and after the sensor needs to ensure that the flow velocity can be completely symmetrically distributed under the reference of the central axis. This is of great value in ensuring the accuracy of the operation of the electromagnetic flowmeter.
At the same time, it is worth noting that the accuracy of the electromagnetic flowmeter may also be affected by the conductivity level of the conductive fluid in the measuring tube. In order to eliminate the adverse effect of this factor on the accuracy of the electromagnetic flowmeter, the measures to be taken are: if it is required by the actual operating conditions of the project, other types of media need to be added inside the pipe with the electromagnetic flowmeter installed, then the corresponding media is added. Work needs to be done in the downstream section of the electromagnetic flowmeter installation. If it is affected by objective factors and needs to add medium upstream, it is necessary to increase the separation distance between the injection area and the installation area of ​​the electromagnetic flowmeter (the basic control requirement is ≥50* measuring the inner diameter of the pipeline). In this way, ensure that the new medium is added. The fluid is more even and smooth through the electromagnetic flowmeter.
During the installation of the electromagnetic flowmeter, it is necessary to ensure that the inside of the flowmeter measuring tube is filled with flowing fluid. The main reason is that in the process of measuring the internal flow level of the electromagnetic flowmeter, the main factors acquired include the cross-sectional area of ​​the motor and the flow velocity of the motor plane. The product of the above two indicators is the measured value finally displayed by the electromagnetic flowmeter. Therefore, the electromagnetic flowmeter measuring tube can ensure the accuracy and reliability of the acquired data only in the full tube state. In the process of installing the electromagnetic flowmeter horizontally, the flowmeter needs to be at the bottom of the pipeline. On this basis, in the case of gas-liquid mixing or solid-liquid mixing, in addition to the installation in the above manner, it is necessary to place the flowmeter in an inclined posture to avoid separation of gas or solid in the mixed flow. , affecting the accuracy of the measurement. It is necessary to do a good job in grounding and liquid connection in the installation of overshoot of the electromagnetic flowmeter. During the application of the electromagnetic flowmeter to measure the fluid flow velocity inside the pipeline, the voltage difference level between the sensor output signal and the electrode is in an equal state.
Therefore, in order to ensure smooth and reliable operation of the flowmeter, it is necessary to set a reference point of zero potential as a reference. In this overshoot, the core of the liquid handling process is: reference point reference for setting the grounding of the conductive liquid inside the pipe to zero potential; and at the same time, the core of the grounding process is to avoid the interference of the electromagnetic flowmeter during the measurement of the fluid flow rate. And provide reasonable safety protection for the electromagnetic flowmeter. At the same time, the grounding treatment can also effectively suppress the noise voltage induced by the electromagnetic induction by the electromagnetic induction, and eliminate the interference to the measurement data. Through the control of the grounding resistance level, the level of the stray current voltage drop of the circuit is significantly reduced, and the method of reducing the common mode interference voltage is achieved, thereby achieving the purpose of consolidating the measurement accuracy of the electromagnetic flowmeter. The specific grounding method is shown in the figure.

Finally, in the installation overshoot of the electromagnetic flowmeter, it is necessary to maximize the distance between the installation area and the magnetic source or the vibration source, and improve the accuracy of the measurement by means of the ground connection. With the support of current technical conditions, it is recommended to control the resistance value of the electromagnetic flowmeter under grounding conditions ≤ 100.0Ω unit. Especially for electromagnetic flowmeters with explosion-proof requirements and lightning protection requirements, the resistance value control standard under grounding conditions should be ≤10.0Ω.
In summary, in addition to the selection and quality control measures for installation, it has an important impact on improving the accuracy of the electromagnetic flowmeter. In the post-operation maintenance management of the electromagnetic flowmeter, it is necessary to do a good job in preventing and controlling the electrode contamination of the electromagnetic flowmeter. Decontamination of contaminated areas. It is also necessary to periodically measure the value of the grounding resistance by a special person to ensure that the electromagnetic flowmeter can operate reliably and efficiently within a safe range and obtain accurate measurement parameters.