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Description of the considerations in the use of electromagnetic flowmeters

Electromagnetic flowmeters are mainly used to measure the volumetric flow in conductive liquids and slurries in closed pipes, including highly corrosive liquids such as acids, alkalis, and salts. Electromagnetic flowmeters are widely used in petroleum, chemical, metallurgy, textile, food, pharmaceutical, paper and other industries as well as environmental protection, municipal management, water conservancy construction and other fields.

Considerations for the use of electromagnetic flowmeters:

(1) The scale of the water supply pipe or wear changes the size of the inner diameter, which will affect the original flow value and cause measurement error. If the inner diameter of the 100mm diameter meter changes by 1mm, it will bring about 2% additional error.

(2) The application of electromagnetic flowmeter has certain limitations. It can only measure the liquid flow of conductive medium, and can not measure the flow of non-conductive medium, such as gas and water for better heating. In addition, the lining needs to be considered under high temperature conditions. Steam flow meter

(3) The electromagnetic flowmeter determines the volume flow rate in the working state by measuring the speed of the conductive liquid. According to the measurement requirements, for liquid media, mass flow should be measured. The flow rate of the medium should be related to the density of the fluid. Different fluid media have different densities and vary with temperature. If the electromagnetic flowmeter converter does not consider the fluid density, it is not appropriate to give only the volume flow at normal temperature.

(4) When the electromagnetic flowmeter is used to measure the viscous liquid with dirt, the sticky substance or sediment adheres to the inner wall or the electrode of the measuring tube, so that the output potential of the transmitter changes, which brings measurement error, and the dirt on the electrode reaches a certain level. Thickness may cause the meter to be unmeasured. Handheld ultrasonic flowmeter

(5) The measurement signal of the transmitter is a small millivolt potential signal. In addition to the flow signal, it also contains some signals that are independent of the flow, such as phase voltage, quadrature voltage and common mode voltage. In order to accurately measure the flow rate, various interference signals must be eliminated to effectively amplify the flow signal. Should improve the performance of the flow converter, it is best to use a microprocessor type converter, use it to control the excitation voltage, according to the measured
Fluid properties Select the excitation mode and frequency to eliminate in-phase interference and quadrature interference. However, the improved instrument structure is complicated and the cost is higher.

(6) The installation and commissioning of the electromagnetic flowmeter is more complicated than other flowmeters, and the requirements are more stringent. The transmitter and converter must be used together and cannot be used with two different types of instruments. When installing the transmitter, the selection from the installation site to the specific installation and commissioning must be carried out in strict accordance with the product specifications. The installation site must be free from vibration and strong magnetic fields. The transmitter and piping must be in good contact and well grounded during installation. The potential of the transmitter is equipotential to the fluid being measured. When using, the gas remaining in the measuring tube must be drained, otherwise it will cause a large measurement error.

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