1. Advantages
(1) Electromagnetic flow meters can be used to measure industrial conductive liquids or slurries.
(2) No pressure loss.
(3) The measurement range is large, and the aperture of the electromagnetic flow transmitter ranges from 2.5mm to 2.6m.
(4) The electromagnetic flowmeter measures the volumetric flow rate of the measured fluid under working conditions, and the measurement principle does not involve the influence of fluid temperature, pressure, density, and viscosity.
2. Disadvantages
(1) The application of electromagnetic flow meters has certain limitations, as they can only measure the liquid flow rate of conductive media and cannot measure the flow rate of non-conductive media, such as heating water with better gas and water treatment. In addition, its lining needs to be considered under high temperature conditions.
(2) Electromagnetic flowmeter determines the volumetric flow rate under working conditions by measuring the velocity of conductive liquids. According to metrological requirements, for liquid media, mass flow rate should be measured, and the measurement of medium flow rate should involve the density of the fluid. Different fluid media have different densities and vary with temperature. If the electromagnetic flowmeter converter does not consider fluid density and only provides volumetric flow rate at room temperature, it is not appropriate.
(3) The installation and debugging of electromagnetic flow meters are more complex and require stricter requirements than other flow meters. The transmitter and converter must be used together, and two different models of instruments cannot be used between them. When installing the transmitter, from the selection of installation location to the specific installation and debugging, it is necessary to strictly follow the requirements of the product manual. The installation site must not have vibration or strong magnetic fields. During installation, it is necessary to ensure good contact and grounding between the transmitter and the pipeline. The potential of the transmitter is equal to the potential of the measured fluid. When using, it is necessary to exhaust the gas remaining in the measuring tube, otherwise it will cause significant measurement errors.
(4) When electromagnetic flow meters are used to measure viscous liquids with dirt, sticky substances or precipitates adhere to the inner wall or electrode of the measuring tube, causing changes in the output potential of the transmitter and resulting in measurement errors. If the dirt on the electrode reaches a certain thickness, it may cause the instrument to be unable to measure.
(5) Scaling or wear on the water supply pipeline that changes the inner diameter size will affect the original flow rate value and cause measurement errors. If the inner diameter of a 100mm caliber instrument changes by 1mm, it will bring about an additional error of about 2%.
(6) The measurement signal of the transmitter is a very small millivolt level potential signal, in addition to the flow signal, there are also some signals unrelated to flow, such as phase voltage, orthogonal voltage, and common mode voltage. In order to accurately measure flow, it is necessary to eliminate various interference signals and effectively amplify the flow signal. The performance of the flow converter should be improved, preferably using a microprocessor based converter to control the excitation voltage. The excitation method and frequency should be selected according to the properties of the measured fluid, which can eliminate in-phase interference and orthogonal interference. But the improved instrument structure is complex and costly.
(7) High price