One-piece electromagnetic flowmeter

Products overview:
ZW series - LDE one-piece electromagnetic flowmeter using the constant current low-frequency rectangular wave three values or dual-bａnd rectangular wave excitation, the advantages of both the rectangular wave field, and overcomes the drawback of sinusoidal magnetic field;Can also eliminate the power supply voltage fluctuation, power frequency and the excitation coil impedance changes caused by the error;And has excellent stability of zero point and is not affected by fluid noise interference.Which has the characteristics of high stability, high reliability.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 a body flowmeter.
Second, the working principle:
ZW - LDE seriesOne-piece electromagnetic flowmeter based on 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.
Applications:
ZW - LDE seriesOne-piece electromagnetic flowmeter is mainly used to measure volume flow of conducting liquid and slurry in the closed pipeline.Such as water, sewage, slurry, pulp, all kinds of acid, alkali, salt solution slurry, food and so on, the electromagnetic flowmeter is widely used in petrochemical, steel, metallurgy, water supply and drainage, irrigation, water treatment, environmental protection sewage total amount control, paper making, medicine, food and other industrial and agricultural sector of the production process flow measurement and control;Apply to the amount of conductive liquid measurement.
Four, flowmeter structure:
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.

Five, the main features:
1, the amount of full digital processing, strong anti-interference ability, reliable measurement, high accuracy, the flow measurement range of up to 150:1;
2, low EMI switching power supply, it is suitable for the power supply voltage variation range is big, EMI resistance performance is good;
3, USES the 16-bit embedded microcontroller processor, a fast calculation speed, high precision, programmable frequency low-frequency rectangular wave excitation, improve the stability of the flow measurement, low power consumption.
4, the SMD components and surface mount technology (SMT), circuit of high reliability;
Have no moving parts, 5, and the pipe unimpeded flow components, almost no additional pressure loss in the measurement;
6, in the field can be on-line modification range according to user's actual needs;
7, measurement results and the velocity distribution, the fluid pressure, temperature, density, viscosity and other physical parameters has nothing to do;
8, high-definition backlit LCD display, full Chinese menu operation, easy to use, simple operation, easy to understand;
9, with RS485 and RS232, Hart and Modbus digital communication signal output.(optional).
10, with functions of self-check and since the argument;
11, total hours recording function, total hours for the unit to record the flow rate, is suitable for the time-sharing measurement system (optional);
12, inside has three integrator can reverse the cumulative amount respectively show positive cumulative integrating quantity and difference, it has not always, can record 16 times time when power supply drop.(optional).
13, infrared carrying manipulator, 115 KHZ communication rate, long distance non-contact operation converter all function (optional).
Six, the technical parameters:
Instrument accuracy: pipeline magnitude 0.5, 1.0;Plug in 2.5 on the Richter scale;
Measuring medium: conductivity is greater than 5 mu S/cm of various liquid and liquid-solid two-phase fluid;
Velocity range: 0.2 ~ 8 m/s;
Working pressure: 1.6 MPa;
Ambient temperature: - 40 ℃ ~ + 50 ℃;
Medium temperature: ptfe lining 180 ℃ or less;
Rubber lining 65 ℃ or less;
Explosion-proof marks: Exmibd Ⅱ BT4;
Explosion-proof number: GYB01349;
Outside magnetic interference: 400 a/m or less;
Enclosure protection: integration type: IP65;
In mold: sensor IP68 (5 meters underwater, rubber lining only);
Converter IP65;
Output signals: 4 ~ 20 ma DC, 0 ~ 750 Ω load resistance;
Communication output: RS485 or CAN bus;
Electrical connections: M20 x 1.5 internal thread, phi 10 cable hole;
Power supply voltage: 90 ~ 220 v AC, 24 V.D C + / - 10%;
Power consumption: 10 or less va.
Seven, 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.
Eight, main advantages and disadvantages are as follows:
1, the sensor structure is simple, the measuring tube has no moving parts, no obstacles to fluid flow throttling components.So when the fluid flow through timing does not cause any additional pressure loss, flow meter is running in one of the flowmeters zui low energy consumption.
2, measurable smudges medium, corrosive medium and clouding the liquid-solid two phase flow of traffic.This is due to internal unimpeded flow meter tube parts, and the measurement of body contact is sounding pipe lining and electrode, the materials can choose according to the nature of the current body.For example, made from poly three fluoride or ptfe lining, can measure all kinds of acid, alkali, salt and other corrosive medium.Adopt wear-resisting rubber lining, is especially suitable for measuring with solid particle slurry, water slurry, wear a large liquid-solid two phase flow and various liquid with fiber and pulp suspension.
3, is a kind of volume flow measuring instrument, in the process of measurement, it is not affected by the temperature of the measured medium, viscosity and density with conductivity (in a certain range.Therefore, electromagnetic flowmeter only after water calibration, it can used to measure the conductivity of liquid flow.
4, output is proportional to the average flow velocity of the measured medium, and under the symmetric distribution of flow (laminar flow and turbulent flow).So the electromagnetic flowmeter range very wide range, the measurement range can be up to 100:1, some even up to 1000:1 working flow range.
5, no mechanical inertia, responsive, can measure the instantaneous pulse flow, also can measure the rate of flow of positive and negative two directions.
6, caliber, very wide range from a few millimeters to a few meters, and the domestic existing diameter up to 3 m's real flow calibration equipment, laid the groundwork for the application and development of electromagnetic flowmeter.
There is still the main deficiencies are as follows:
1, cannot be used for measuring gas, steam and liquid contains a lot of gas.
2, low cannot be used to measure the conductivity of liquid medium, such as the petroleum products or organic solvent such as medium, the electromagnetic flowmeter is powerless.
3, ordinary electromagnetic flow meter used in industry due to the measuring tube lined with the limitation of materials and electrical insulation materials, can not be used in measuring high temperature medium;If without special treatment, also cannot be used for the measurement of low temperature medium, in order to prevent the measuring tube condensation (frost) destruction of insulation.
4, the influence of electromagnetic flowmeter vulnerable to external electromagnetic interference.
Nine,The installation of the flowmeter requirements:
The choice of installation environment
1, should as far as possible away from strong electromagnetic field equipment.Such as big motor, transformer, etc.
2, the installation place should not have a strong vibration, environmental temperature change is not big.
3, easy to install and maintenance.
The choice of the installation position
1, sensors, flow mark on the direction of the measured medium flow and the pipe must be consistent.
2, installation location must ensure that the measuring tube in the book is full of measured medium.
3, and the choice of fluid flow pulse smaller places, which should be far away from the pump and local resistance (valve, elbow, etc.)
4, the measurement of two-phase fluid, should choose is not easy to cause the location of the phase separation.
A negative pressure, avoid installed in a tube of five places.
6, when makes the electrode measured medium, measure the tube inner surface adhesion, scaling, suggest the measuring tube flow velocity of no less than 2 m/s.
At this time can use reducing pipe diameter slightly smaller than the process.For uninterrupted flow in the process piping cleaning electrode and the measuring tube, sensor can be used parallel installations, and cleaning.
The choice of the installation site
In order to make the transmitter work stability, when choosing the location should be paid attention to the following requirements:
1, try to avoid strong ferromagnetic objects and concrete equipment of electromagnetic field (such as a big motor, transformer, etc.), so as to avoid the magnetic field of magnetic field effect sensor and traffic information.
2, should be installed in a dry and ventilated place, should not be in damp, easy seeper place of installation.
3, should try to avoid weathered, avoid environmental temperature is higher than 45 ℃ and relative humidity is more than 95.9%.
4, choose to facilitate maintenance and convenient place.
5, flow meter should be installed in the pump back end, never on the suction side of the installation;Valve should be installed in the downstream flow meters.
Ten, notable matters of installation:
1, the electromagnetic flowmeter sensor should be installed vertically, and fluid flows from bottom to top, in order to meet the solid and liquid two is in a state of mixed.The reason is that if there is solid in the medium (sand, gravel particles, etc.) are prone to precipitation.Have fish and weeds in another line of fish swimming in the pipeline, will cause the flowmeter output swing;Hang back and forth near the electrode weeds can also cause the output of the meter is not stable.Set at the entrance of upstream flow meter metal screen blocking fish and weeds into the measuring tube.
2, the electromagnetic flowmeter to prevent negative pressure pipe set improper operation will cause negative pressure sensor inside.When closed, downstream of the valve in the flow meter at the same time, if the temperature is higher than the temperature of the fluid.Contraction after cooling, the pipe pressure is in danger of forming negative pressure.The negative pressure caused by the lining and metal vessel, cause leakage electrode.
3, near the electromagnetic flowmeter with negative pressure to prevent valve, open the valve on atmospheric pressure, in order to prevent to produce negative pressure in the sensor.Electromagnetic flowmeter downstream by a vertical line, if use flow upstream of the valve to close or adjust the flow sensor, the sensor will form a negative pressure measuring tube.In order to prevent negative pressure, need to add back pressure or use downstream to adjust and close the flow valve.
4, proper maintenance space, large diameter flowmeter are often installed in instrument well, for pipe installation, wiring, inspection and maintenance convenience, need to have the appropriate space.For observation, connection and maintenance convenience, instrument installation should have a certain height from ground, in order to facilitate cleaning, installation.

11, 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:

Twelve, 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:

13, 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.