The current use of electromagnetic flowmeters has been very extensive, coupled with the advancement of science and technology, the continuous improvement of the processing level, the function of electromagnetic flowmeters is also more powerful, and the accuracy is also improved than before. How to judge whether an electromagnetic flowmeter is good or bad . There are many methods and different methods. In the inspection stage of the production workshop, the resistance of the magnetic coil is measured by a multimeter, and the electrical JI and liquid contact resistance are used to comprehensively judge the performance of the instrument.
The superiority of the electromagnetic flowmeter is reflected in the following points, because the electromagnetic flowmeter is a volume flow measuring instrument. During the measurement process of the instrument, it is not affected by the temperature of the measuring medium. The influence of physical properties (within a certain range) such as viscosity, density and conductivity. Therefore, the meter can be used to measure the flow of other conductive liquids only after being calibrated with water, and no additional means are needed for correction. The transmitter of the electromagnetic flowmeter has a simple structure, no moving parts, and no throttling parts that hinder the flow of fluid, so when the fluid passes through it will not cause any additional pressure loss, and it will not cause such as wear, blockage, etc. It is especially suitable for measuring liquid-solid two-phase fluids such as ore slurry with solid particles, sewage, and various viscous slurries. Similarly, because it has no moving parts in its structure, it can be made into electrical JI by attaching a corrosion-resistant insulating lining and selecting corrosion-resistant materials, which has good corrosion resistance and can be used for measurement of various corrosive media.
How to choose the electromagnetic flowmeter, which one to choose, how to install it, how to install it correctly, and how to deal with the failure phenomenon? There will be many problems in the selection of applications, so we must correctly select and install special instruments. How to judge whether the electromagnetic flowmeter is good or bad: Use visual inspection and instrument method to check whether the excitation coil resistance of the sensor, the insulation resistance between the signal wires, the grounding resistance and other items meet the standards before leaving the factory. The electromagnetic flowmeter converter Whether the zero point, output current, etc. meet the accuracy requirements. The specific detection method is:
(1) Measure the resistance value of the excitation coil to determine whether the excitation coil has an inter-turn short circuit (the resistance value between the line number "7" and "8"). The resistance value should be between 30 ohms and 170 ohms. If the resistance is the same as the factory record, the coil is considered good, and the magnetic field strength of the electromagnetic flowmeter sensor is indirectly evaluated.
(2) Measure the insulation resistance of the excitation coil to the ground (measurement line number "1" and "7" or "8") to determine whether the sensor is damp, and the resistance value should be greater than 20 megohms.
(3) Measure the electrical JI and liquid contact resistance (measurement line numbers "1" and "2" and "1" and "3"), and indirectly evaluate the electrical JI and the general condition of the lining layer surface. For example, whether the deposited layer is attached to the surface of the electric JI and the lining layer, and whether the deposited layer is conductive or insulating. The resistance value between them should be between 1 kiloohm and 1 megohm, and the resistance values of wire numbers "1" and "2" and "1" and "3" should be roughly symmetrical.
(4) Close the valve on the pipeline and check the zero point of the electromagnetic flowmeter when it is full of liquid and no liquid is flowing. Make appropriate adjustments based on the situation.
(5) Check the insulation resistance of each core wire of the signal cable and excitation cable, and check whether the shielding layer is intact.
(6) Use the GS8 calibration instrument to test the output current of the converter. When zero flow is given, the output current should be: 4.00mA; when 100% flow is given, the output current should be: 20.00mA. The error of the output current value should be better than 1.5%.
(7) Test the excitation current value (between the converter terminals "7" and "8"). The positive and negative values of the excitation current should be within the specified range, roughly 137 (5 percent) mA.
During the installation and use of the instrument, pay close attention to the influence of the external environment of the electromagnetic flowmeter: for example, the excitation line and the signal line are laid in the same pipeline, the excitation line and the signal line are parallel to the high-voltage cable, and there are large transformers or motors around. The influence of factors on the operating accuracy of the electromagnetic flowmeter is evaluated. This evaluation mainly uses the visual method to observe whether the electromagnetic flowmeter in operation has sudden changes or fluctuations.