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Classification of electromagnetic flowmeter

Date:2020-01-07 source:

Electromagnetic flowmeter in the current stage of chemical plant manufacturing and other industrial production sites, the demand is very large.In general, when it comes to the accurate measurement of liquid, the first consideration is the electromagnetic flowmeter. In terms of its own precise measurement characteristics, the electromagnetic flowmeter has very significant advantages in the whole process of accurate measurement.

Classification of electromagnetic flowmeter

There are many kinds of classification methods of electromagnetic flowmeter, and there are often many types of commodities under each classification that match each other. People should have a basic grasp of the motor selection of commodities, which can guide people's motor selection very well and ensure the proper application of commodities.This article has made 6 kinds of basic classification to the electromagnetic flowmeter, below gives the introduction to everyone.

Classification of electromagnetic flowmeter

First, according to the sensor and converter assembly method classification type electromagnetic flowmeter: type is the electromagnetic flowmeter is the most widely used way, sensor connection pipeline, converter installed in the instrument room or easy to close to the sensor surrounding, a distance of tens to hundreds of meters.In order to avoid the invasion of external noise, the shielding cable is usually two layers shielded.When the liquid with low conductivity is accurately measured and the aggregation exceeds 30m, in order to avoid the attenuation of data signal caused by part of the capacitor in the cable, the inner shield is also the shielded driver that is required to connect the low impedance source with the core with the same potential difference.The separated converter can eliminate the extreme natural environment on the spot, and it is more convenient to check, adjust and set the main parameters of the electronic components.

Integrated electromagnetic flowmeter: the sensor and converter are assembled together to immediately output the dc current (or frequency) specification data signal, in effect becoming an electromagnetic flow transmitter.The all-in-one model shortens the connection length of the power line and the excitation line between the two, and makes them connected externally and concealed in the instrument, thus reducing the attenuation of data signal and the invasion of electromagnetic wave noise in indoor space.

The same exact measurement circuit and the split-body comparison can measure the lower conductivity of the liquid.It cancels the wiring of power line and excitation line, simplifies the electrical connection, and makes the price and installation cost of instrument relatively reasonable.With the technical development of two - wire instrument, one - body instrument will have a rapid development trend.But if because pipeline arranges limit, install in the site that does not get close to easily, maintain trouble.In addition, the electronic components of the converter installed in the pipeline will be subject to great limitations of hydrodynamic temperature and tube vibration.

Two, according to the total flow sensor electrode is not in contact with the measured liquid contact classification contact type electrode -- and liquid contact electrode is EMF traditional structure, generally a pair of electrodes, large size electromagnetic flowmeter industry effective two pairs of electrodes.Non-tubular EMF is also effective for 3 pairs of motors or strip electrodes.

Non-contact type electrode -- large scale electrode is close to the outer surface of the inner lining (or insulating layer measuring tube) to detect the total flow data signal by means of capacitor coupling.The preamplifier is placed in the sensor only by the electrode, the excitation frequency is higher than the general EMF, for 50/2hz, also more than 100Hz.This kind of instrument is not easy to cause electrode passivation treatment, air oxidation, catalyst efficiency and other electrode surface effect noise, also there is no flow noise and slurry noise.The inner surface of the liner covers the non-conductive layer such as grease or the thin insulating layer and the solid layer is not easy to endanger the measurement.However, if the soil layer is such a conductive film, the instrument will not be marked.Some foreign instrument manufacturers call this instrument electrode-free electromagnetic flowmeter.

Flange connection shall be classified according to the connection mode of total flow sensor and pipeline. Flange connection is a traditional connection mode. There are connection flanges on both sides of the sensor.The large size sensor of electromagnetic flowmeter adopts this interface mode.Both volume and net weight are larger than the clamp-on interface.The length between two flange faces of DN15 ~ 600mm electromagnetic flowmeter has been standardized by the international organization for standardization (ISO13359;1998) give unity.

Flange clamping connection: the connection method developed in recent years when flange clamping connection is adopted. The sensor of the electromagnetic flowmeter has no flange, and the pipe system is connected between the two flanges of the pipeline with very long bolts.This method has a small volume and light weight, and is highly adaptable to different working pressure specifications and flange holes of standard piping.However, it is only suitable for the smaller tube (less than 200mm), bearing lower liquid pressure.

Clamp connection: the clamp-type connection keeps the electromagnetic flowmeter removed and installed quickly, facilitating routine cleaning.

Bolt connection: this kind of electromagnetic flowmeter is widely used in pharmaceutical industry, food industry and medicine preparation and introduction.Bolt connection is also more used in crude oil, geological exploration and other 16 ~ 25MPa high-pressure irrigation or cement slurry flow measurement, the appearance of the external thread is ladder.

Four, according to the output signal coupling and excitation (or switch power supply) online style classified four wire electromagnetic flowmeter, four wire system are the output of the traditional electromagnetic flowmeter signal lines and power plug (or total flow field between the sensor and the sensor cable) by two respective groups (2 pieces of four wire transmission line, is the key to today's style.Two - line electromagnetic flowmeter - current temperature, operating pressure/differential pressure, total flow and material level, and other parameters on the spot meters tend to output data signal and power supply with the power line two - line instrument development trend.

Two - wire instrument does not need mains switching power supply, and electromagnetic flowmeter is often installed in remote places without mains supply and demand balance, the use of two - wire system can save the cost of voltage wiring project.The design idea of the balance of supply and demand of the two-line electromagnetic flowmeter is divided into the balance of supply and demand of zero signal output current (4mA), the balance of supply and demand of data output over zero, and the balance of supply and demand of rechargeable batteries (or solar cells).Rechargeable battery power system type electromagnetic flowmeter and inductance type water meter are integrated and equipped to eliminate stains and other voltage introduction difficulties in big city water pool or field sewage treatment.Some types of rechargeable batteries have a service life of 1-2 years, while some have a service life of nearly 8-10 years.

Pipeline electromagnetic flowmeters are classified according to the total flow sensor structure: pipeline structure, such as the traditional electromagnetic flowmeter structure, the total flow sensor contains accurate measurement pipe connected to the pipeline system software.Plug-in electromagnetic flowmeter: the plug-in total flow sensor is essentially an electromagnetic induction current sensor. The excitation coil and electrode are assembled into a rod-like structure, which is inserted from the hole in the pipeline under test, and the measured water flow is calculated by the exponential product of sulfuric acid of the preset pipeline area of the converter.In addition to the single point of "water flow", there are also more side of the "runoff speed".This kind of instrument is suitable for large and medium-sized pipelines, because it is the accurate measurement of partial water flow to calculate the total flow of fluid, the accurate measurement precision should be less than the short tube type, generally only used for process management, not suitable for the use of trade carryover metrological verification, but the price is relatively cost-effective.

6. General type according to main USES: in metallurgical industry, petrochemical industry, paper industry, printing and dyeing factory, textile, water supply, wastewater treatment and other industrial production, split body type medium and large size flange interface is generally adopted;Pharmaceutical, microbiology, bio-chemical industry and other common micro specifications, diameter meters, a set of clamping interface or bolt connection method of electromagnetic flowmeters available sites.

Flameproof type: flameproof electromagnetic flowmeter is used in the field with inflammable atmosphere.Because of the large majority of electromagnetic flowmeter several return current kinetic energy is very large, generally designed into explosion-proof, sand mold, pouring seal type and air tightness type.However, the excitation output power of some electromagnetic flowmeters has been greatly reduced, which is also the safety culture type, that is, the safety flame type referred to before. Part of the total flow sensor and the transformation part are standard components, all installed in the risk area.



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