High-frequency electromagnetic flowmeter

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High-frequency electromagnetic flowmeter is specially designed for water supply enterprises water me…

Products overview:
ZW - LDE seriesHigh-frequency electromagnetic flowmeterThe accuracy of measurement is not affected by fluid density, viscosity, temperature, pressure and conductivity changes, the influence of sensor induction voltage signal, and a linear relationship between the average flow, so the high precision measurement.In measuring the pipe flow, so there is no additional pressure loss;Measurement of the pipe have no moving parts, so very long sensor life.Due to the induced voltage signal is formed in the whole space full of magnetic field, is the average of the pipeline on the surface of the load, the amount of straight pipe required sensor is shorter, length of 5 times the pipe diameter.Sensor part only lining and electrode contact with the liquid being measured, as long as reasonable selective electrode and lining materials, corrosion resistance and wear resistance.

Second, the working principle:
ZW - LDE seriesHigh-frequency electromagnetic flowmeterAccording to Faraday electromagnetic induction principle, with the sounding pipe axis and the magnetic field lines in the vertical tube wall installed on a pair of detecting electrodes, when conducting liquid along the measuring tube axis movement, conductive liquid cutting lines of magnetic force induced electric potential, the induction electric potential by two detection electrodes detection, numerical size and flow into a direct ratio, its value is: E = KBVD type:
E - induction electric potential;
K - factor related to the magnetic field distribution and the axial length;
B - magnetic induction intensity;
V - conductive liquid average flow velocity;
D - electrode gap;(the measuring tube diameter)
Sensor will be induced potential E as traffic signal, sent to the converter, amplifying, transform filter with a series of digital processing, USES dot matrix LCD display with backlight instantaneous flow and cumulative flow.Converter has 4 ~ 20 ma output, alarm output and frequency output, and is equipped with RS - 485 communication interface, and supports HART and MODBUS protocol.

Applicable occasions:
ZW - LDE seriesHigh-frequency electromagnetic flowmeterAccording to the scene of the meet at the same time, also can output 4 ~ 20 ma current signal for records, adjust and control, has been widely used in chemical industry, environmental protection, metallurgy, medicine, paper making, water supply and drainage and other industrial technology and management.Electromagnetic flowmeter in addition to the general conductive liquid flow can be measured, can also be measured liquid-solid two phase flow, high viscosity fluid and salt, strong acid, strong alkali liquid volume flow.

Part four, :
Electromagnetic flowmeter is composed of sensors and switches, sensors installed on the measuring pipe, the converter can be connected to the sensor combination together referred to as electromagnetic flowmeter, a size converter is installed within 100 meters of within 30 meters away from the sensor or occasions, are connected by a shielded cable is called separation between type electromagnetic flow meter.Corrosion is the main component of the electromagnetic flowmeter sensor: the measuring tube, electrode, excitation coil, magnetic yoke iron core and shell.

Five, the main features:
1, instrument structure is simple, reliable, have no moving parts, long working life.
2, no closure choke parts, there is no pressure loss and flow blocking phenomenon.
3, no mechanical inertia, fast response and good stability, can be applied to automatic testing, adjusting and SPC system.
4, the measurement precision is not affected by the type of measured medium and its temperature, viscosity, density, the influence of physical parameters such as pressure.
5, adopt ptfe or rubber lining material and Hc, Hb, 316 l, the different combination of electrode materials such as Ti can adapt to the needs of different medium.
6, with pipeline, plug-in, such as a variety of flow meter type.
7 block, using EEPROM memory, measuring operational data storage safe and reliable protection.
8, integration and separation of two kinds of model.
9, high-definition LCD backlit display.
Six, the technical parameters:
1, precision instrument: pipeline magnitude 0.5, 1.0;Plug in 2.5 on the Richter scale are unlikely.
2, measuring medium: conductivity is greater than 5 mu S/cm of various liquid and liquid-solid two-phase fluid.
3, velocity range: 0.2 ~ 8 m/s.
4, work pressure: 1.6 MPa.
5, environmental temperature: - 40 ℃ ~ + 50 ℃.
6, medium temperature: ptfe lining 180 ℃ or less;Rubber lining material 65 ℃ or less.
7, explosion-proof marks: Exmibd Ⅱ BT4.
8, explosion-proof number: GYB01349.
9, outside magnetic interference: 400 a/m or less.
10, shell protection: integration type: IP65;
In mold: sensor IP68 (5 meters underwater, rubber lining only);Converter IP65.
11, the output signal: 4 ~ 20 ma DC, load resistance Ω 0 ~ 750
12, communication output: RS485 and CAN bus
13, electrical connections: M20 x 1.5 internal thread, phi 10 cable hole
14, power supply voltage: 90 ~ 220 v AC, 24 + / - 10% V.D C
15, power consumption: 10 or less va.
Seven, the structure form:
1, the sensor:
Sensor is mainly composed of measuring tube and electrode, excitation coils, iron core, magnetic yoke and shell.
A, measuring catheter: by stainless steel tube, the lining and the connecting flange, as the carrier of measured liquid measurement working conditions on site.
B, measuring electrode: installed in the measuring tube inside wall, and the axial direction perpendicular to a pair of electrodes to measure liquid signal generation.
: c, excitation coil in a magnetic field measurement of intraductal two excitation coil.
D, iron core and magnetic yoke: the excitation coil of the magnetic field generated import liquid, and the magnetic circuit.
E, shell: instrument packaging.
2, converter that is smart the secondary table, it will flow signal amplification processing, single chip microcomputer after the operation, can display flow, total amount, and can output pulse and analog current signal, used in the measurement or control of fluid flow.
3, product assembly form: it into a shape and size in two forms.
A, a shape: mounted sensors and switches.
B, size: separation installation sensor and converter, through the connecting cable form flow metering system.
C, in order to adapt to the measurement demands of the different medium, the lining of sensor and electrode materials can have many choices.

Eight, according to excitation methods of classification:
To produce a uniform constant magnetic field, it needs to choose a suitable way of excitation.Such as divided according to the field current mode, have a dc field, ac (or other frequency) power frequency excitation, low-frequency rectangular wave excitation and dual-band rectangular wave excitation.
1, the dc excitation
Dc excitation method with direct current (dc) or use a magnet to produce a uniform magnetic field is constant.The dc excitation transmitter is affected by the ac electromagnetic interference is very small, so you can ignore the influence of the liquid in the self inductance.But using dc magnetic field is easy to make by measuring the electrolyte fluid of the pipe is polarized, the electrolyte by electrolysis in the electric field, produce positive and negative ions, in under the action of electric field force, ran to the anode, anion cation ran to the cathode, which will result in positive and negative electrodes were surrounded by ions of opposite polarity, seriously affect the normal work of the instrument.So, dc excitation only commonly used for measuring the liquid electrolyte, such as the liquid metal flow of mercury (room temperature and high temperature of liquid steel, lithium, potassium), etc.
2, ac excitation
Industrial use of electromagnetic flowmeter, most used (50 hz) power supply power frequency ac excitation method to produce alternating magnetic field, to avoid the dc excitation on the surface of the electrode polarization interference.But the use of ac excitation will bring a series of electromagnetic interference problem, such as orthogonal interference, in-phase interference, zero drift, etc.).Ac excitation is now replaced by low frequency square wave excitation.
3, low frequency square wave excitation
Low frequency square wave excitation waveform has two values (positive - negative) and three values (positive - zero - negative - zero) two kinds, the frequency of power frequency usually 1/2 ~ 1/32.Low frequency square wave excitation can avoid orthogonal electromagnetic interference of ac magnetic field, power frequency interference caused by distributed capacitance, inhibition of ac magnetic field within the tube wall and fluid caused by eddy current, dc excitation polarization phenomenon.

The preparing work before nine, run:
1, put into operation after installation wiring should be checked again before the installation, wiring is correct.(the size)
2, before the bed bottom valve is opened, the sensor after the valve closed, let the sensor with the medium.
3, after the completion of the preparation, upstream of the valve to open the first sensor, then slowly open the downstream of the valve, observe the converter instantaneous flow display should be toward the direction of change, that signal lines in the right direction.Otherwise, will signal A and B connection swap position.(the size)
4, open the sensor before and after the valve, drainage for a few minutes, the gas discharge tube.
5, close the sensor downstream of the valve, then close upstream of the valve, the measured medium is inside the sensor.And then to form a complete set of adjustment.Sensor and converter matching coefficient of zero adjustment and instrument set converter specifications, please read them.

Ten, the straight pipe installation requirements:
Electromagnetic flowmeter sensor of straight pipe upstream and downstream of the installation points has certain requirements, otherwise it will affect the accuracy of measurement.
1, if the sensor installation point upstream of reducer, sensors upstream should be not less than 15 d straight pipe sections, such as the downstream straight pipe section should be not less than 5 d.
2, if the sensor is installed upstream of point have divergent tube, sensor should not be less than 18 d upstream straight pipe sections, such as the downstream straight pipe section should be not less than 5 d.
3, if the sensor installed upstream of point under the 90 ° elbow or sub, sensors upstream should be not less than 20 d straight pipe sections, such as the downstream straight pipe section should be not less than 5 d.
Upstream of four, if the sensor installed on the same plane has two 90 ° elbow, sensor should not be less than 25 d upstream straight pipe sections, such as the downstream straight pipe section should be not less than 5 d.
Upstream of 5, if the sensor installed in different plane has two 90 ° elbow, sensors upstream should be not less than 40 d straight pipe sections, such as the downstream straight pipe section should be not less than 5 d.
6, flow control valve or pressure regulating valve installed on the downstream side of the sensor 5 d as far as possible, if must be installed in the upstream of the sensor, the sensor should not be less than 50 d upstream straight pipe sections, such as the downstream straight pipe section should be not less than 5 d.
Pay special attention to
1, sensors installed upstream of point relatively close if equipped with valve, switch valve and affect the service life of the sensor is great, very easy to cause damage to sensor.
2, sensors to avoid the overhead of very long pipe installed on the sensor, so that over time, as the drop sensor is very easy to cause between the sensor and the flange seal leakage, if necessary when installation, must be set separately in the upstream and downstream of sensor 2 d pipe clamp device.

11 and the matters needing attention during installation.
1, the axis of the measuring electrode must be similar to horizontal direction;
2, measuring the pipe must be completely filled with liquid.
3, less flowmeter zui ahead to have 5 * D for flow meter diameter (D) the length of the straight pipe, the rear zui to have less 3 * D for flow meter diameter (D) the length of the straight pipe;
4, the direction of fluid flow and the direction of arrow flowmeter;
Five should have can be damaged by vacuum meter, the pipe lining, special attention should be paid;
6, near the flow meter should be no strong electromagnetic field;
7, shall have plenty of space, near the flowmeter to installation and maintenance;
8, if measuring pipeline vibration, the flowmeter should be fixed on both sides of bearing when measuring the mixed liquid of different medium hybrid point and the distance between the flowmeter zui to have less 30 x D for flow meter diameter (D) the length of the cleaning and maintenance for the convenience of the flowmeter, should install bypass pipe.
Twelve, grounding protection, must pay attention to the following: 
1, sensor, converter should be separate grounding, never even on the motor, process piping, grounding resistance should be less than 10 ohms. 
2, sensor measurement of tube and shell, shielded wire, converter and secondary instrument must be grounded. 
3, sensors, converters, grounding on the scene, to the shield in the control room side of the secondary instrument grounding, not multiterminal grounding, lest introduced due to different potential interference. 
4, sensors installed in a metal tube, the sensor can be grounding wire connected to the pipe flange according to the requirement of the factory, the formation of reliable grounding instrument ground should be an independent site, can not share other electrical equipment grounding.

13, the main technical data:

1, the whole machine and the technology of sensor data:

2, converter technology data:

3, the choice of the lining:

4, import protection flange and the choice of grounding flange ring (or ground) :

5, the choice of electrode:

14, correct selection:

Instrument selection is very important work in instrumentation, relevant data show that the instrument in two-thirds of faults in the practical application is instrument error caused by selection or wrong installation, please pay special attention to.

1, collect data:

By measurement of body composition;
Large flow, small flow;
Z high work pressure;
, z z high temperature low temperature;

2, range scope confirmation:

General industrial use measured medium velocity of electromagnetic flowmeter with 2 ~ 4 m/s advisable, under special circumstances, z low velocity should not be less than 0.2 m/s, high z should be not more than 8 m/s.If the medium containing solid particles, commonly used flow rate should be less than 3 m/s, prevent excessive friction lining and electrode;For viscous flow, the velocity can choose more than 2 m/s, larger velocity help eliminate electrode automatic on the effect of viscous material, to improve accuracy of measurement.

Under the condition of the range of Q have been identified, according to the velocity V can be decided to the size of the flow meter diameter D, the range of the values calculated by the next type:

Q = PI D2V / 4
Q: flow (㎡ / h) D: pipe diameter V: velocity (m/h)

Electromagnetic flow meter range of Q zui flow value should be greater than expected, the flow of the normal value in a full scale slightly greater than the flowmeter calibration 50 is advisable.

3And the reference flow range:

4, selection of code:

15, design selection and ordering information:

1, the measured medium: name, composition, status, electrical conductivity and electrical conductivity;

2, working temperature (℃);

3, work pressure (Mpa);

4, the pipe diameter (DN), the smallest, normal, scope of quantity (m3 / h);

5, corrosion resistance, wear resistance, whether there is a negative pressure;

6, installation requirements and the environment: a body or fission, signal output, communications, power supply;

7, installation environment: protection grade and explosion-proof requirements.

After-sales service commitment:

1, from the date of signing of the contract, I in the way provided for products of the company offers free maintenance and maintenance service, commitment to lifelong maintenance service;

2, jiangsu wei measurement and control instrument co., LTD. Sales manager will be in regular contact with customers, understand the usage of products, and solve the problems of the customers to use in the process of produce, free of charge to provide technical support;

3 the man-made damage is found, the warranty period, our company is responsible for the maintenance, and the resulting maintenance fee;

4, product quality problems or are not satisfied with product, the user can choose unconditional return, wei tt&c don't charge any fees, appear quality problem, bear the freight back and forth.