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Electromagnetic flowmeter strengths and defects analysis Flowmeter quotation Selection calculation

Electromagnetic flowmeter strengths and defects

1. Strengths
(1) Electromagnetic flowmeters can be used to measure industrial conductive liquids or slurries.
(2) No pressure loss.
(3) The measuring range is large, and the diameter of the electromagnetic flow transmitter is from 2.5mm to 2.6m.
(4) The electromagnetic flowmeter measures the volume flow rate of the fluid under test, and the measurement principle does not touch the influence of the temperature, pressure, density and viscosity of the fluid.
2, defects
(1) 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 fabric needs to be considered under high temperature conditions.
(2) The electromagnetic flowmeter determines the volume flow rate under the working condition by measuring the speed of the conductive liquid. According to the measurement requirements, regarding the liquid medium, the mass flow rate should be measured, and the flow rate of the medium should be measured to the density of the fluid. Different fluid media have different densities, and
Temperature changes. If the electromagnetic flowmeter converter does not consider the fluid density, it is not appropriate to give only the volume flow at normal temperature.
(3) The device and debugging of the electromagnetic flowmeter are more messy than other flowmeters, and the requirements are more severe. The transmitter and converter are necessary to use together, and the two can not be used with two different types of appearance. When selecting a transmitter, from the selection of the location of the device to the detailed commissioning of the device,
It is necessary to strictly follow the requirements of the product specification. The location of the device must not oscillate and there should be no strong magnetic fields. It is necessary to have excellent contact and excellent grounding of the transmitter and piping during installation. The potential of the transmitter is equipotential to the fluid being measured. In the application, it is necessary to exhaust the measurement tube
The gas left, otherwise it will form a large measurement error.
(4) When the electromagnetic flowmeter is used to measure the viscous liquid with dust, 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 is changed, which brings measurement error, and the dust and dirt on the electrode must arrive. Thickness may cause the appearance to be unmeasurable.
(5) The fouling or wear of the water supply pipeline changes the inner diameter scale, which will affect the original flow value and form the measurement error. If the inner diameter of the 100mm diameter is changed by 1mm, it will bring about 2% additional error.
(6) The measurement signal of the transmitter is a small millivolt potential signal. In addition to the flow signal, it is also noisy with some flow-independent signals, such as phase voltage, quadrature voltage and common mode voltage. In order to accurately measure the flow, it is necessary to eliminate various disturbance signals, and it is useful to expand the flow signal.
number. The function of the flow converter should be improved. It is best to use a microprocessor type converter to control the excitation voltage. The excitation method and frequency can be selected according to the nature of the fluid to be tested, and the in-phase disturbance and the orthogonal disturbance can be removed. However, the improved appearance of the structure is messy and the cost is higher.

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