1、 Product Overview:

ZW-LDE seriesElectromagnetic FlowmeterIt is an induction instrument that measures the volume flow rate of conductive medium inside a tube based on Faraday's law of electromagnetic induction. It uses embedded microcontroller technology to achieve digital excitation, and adopts CAN fieldbus on the electromagnetic flowmeter, achieving the highest level of technology. While meeting on-site display requirements, it can also output 4-20mA current signals for recording, adjustment, and control purposes. In addition to measuring the flow rate of general conductive liquids, the meter can also measure the volumetric flow rates of liquid-solid two-phase flow, high viscosity liquid flow, and salt, strong acid, and strong alkali liquids.

Integrated electromagnetic excitation utilizes constant current low-frequency ternary rectangular waves or dual frequency rectangular waves, which not only has the advantages of rectangular wave magnetic fields, but also overcomes the disadvantages of sine wave magnetic fields; It can also eliminate errors caused by fluctuations in power supply voltage, changes in power supply frequency, and changes in excitation coil impedance; And it has zero stability and is not affected by fluid noise interference. Therefore, it has the characteristics of high stability and high reliability. An electromagnetic flowmeter consists of a sensor and a converter. The sensor is installed on the measuring pipeline, and the converter can be combined with the sensor to form an integrated flowmeter.

The split type electromagnetic flowmeter adopts a split type design, which is convenient for maintenance and increases the service life of the electromagnetic flowmeter. Wall mounted flow converter effectively protects the sensor conversion circuit and is beneficial for corrosion prevention, moisture resistance, and waterproofing. The product has simple wiring and easy installation. Split electromagnetic consists of sensors and converters. The sensors are installed on the measuring pipeline, while the converters are installed within 30 or 100 meters of the sensors. The two are connected by shielded cables to measure the volumetric flow rate of conductive liquids. The main components of the sensor are: measuring tube, electrode, excitation coil, iron core, and magnetic yoke housing. Mainly used to measure the volumetric flow rate of conductive liquids and slurries in closed pipelines.

2、 Working principle:
ZW-LDE seriesElectromagnetic FlowmeterAccording to Faraday's principle of electromagnetic induction, a pair of detection electrodes are installed on the tube wall perpendicular to the axis of the measuring tube and the magnetic field lines. When the conductive liquid moves along the axis of the measuring tube, it cuts the magnetic field lines and generates an induced potential. This induced potential is detected by the two detection electrodes, and its value is proportional to the flow rate. Its value is E=KBVD equation:
E - Induced potential;
K - coefficient related to magnetic field distribution and axial length;
B - Magnetic induction intensity;
V - average flow velocity of conductive liquid;
D - electrode spacing; (Measuring the inner diameter of the tube)
The sensor uses the induced potential E as a flow signal, which is transmitted to the converter. After amplification, transformation, filtering, and a series of digital processing, the instantaneous and cumulative flow rates are displayed on a backlit dot matrix LCD. The converter has 4-20mA output, alarm output and frequency output, and is equipped with communication interfaces such as RS-485, and supports HART and MODBUS protocols.
3、 Application scenarios:
ZW-LDE seriesElectromagnetic FlowmeterMainly used to measure the volumetric flow rate of conductive liquids and slurries in closed pipelines. Such as water, sewage, mud, pulp, various acids, alkalis, salt solutions, food slurries, etc., are widely used in industries such as petroleum, chemical, metallurgical, textile, food, pharmaceutical, papermaking, as well as environmental protection, municipal management, water conservancy construction and other fields.
4、 Structural form:
1. Sensor:
The sensor mainly consists of a measuring conduit, measuring electrodes, excitation coils, iron cores, magnetic yokes, and a housing.
a、 Measurement catheter: composed of stainless steel catheter, lining, and connecting flange, it is a carrier for measuring the on-site working conditions of the measured liquid.
b、 Measurement electrode: a pair of electrodes installed on the inner wall of the measurement catheter, perpendicular to the axial flow direction, to generate signals for the measured liquid.
c、 Excitation coil: The upper and lower excitation coils that generate a magnetic field inside the measuring conduit.
d、 Iron core and magnetic yoke: Introduce the magnetic field generated by the excitation coil into the liquid and form a magnetic circuit.
e、 Shell: Instrument outer packaging.
2. Converter:
It is an intelligent secondary meter that amplifies and processes the flow signal. After being operated by a microcontroller, it can display the flow rate, cumulative measurement, and output signals such as pulses and analog currents for measuring or controlling fluid flow.
3. Product assembly form:
It is divided into two forms: one-piece and split type.
a、 Integrated: The sensor and converter are installed together.
b、 Split type: Sensors and converters are installed separately, forming a flow metering system through connecting cables.
c、 To meet the requirements of measuring different media, there are multiple choices for the lining and electrode materials of sensors.

5、 Main features:
1. The instrument structure is simple, reliable, without movable parts, and has a long working life;
2. No flow blocking components, no pressure loss or fluid blockage phenomenon;
3. No mechanical inertia, fast response, good stability, can be applied to automatic detection, adjustment, and program control systems;
4. The measurement accuracy is not affected by the type of measured medium and its physical parameters such as temperature, viscosity, density, pressure, etc;
5. Different combinations of PTFE or rubber lining materials and electrode materials such as Hc, Hb, 316L, Ti can adapt to the needs of different media;
6. There are various flow meter models available, including pipeline type and plug-in type;
7. Using EEPROM memory, the measurement and operation data storage protection is safe and reliable;
8. It has two types: integrated and separated;
9. High definition LCD backlit display.
6、 Technical parameters:
1. Instrument accuracy: pipeline type 0.5 level, 1.0 level; Insertion type 2.5 level.
2. Measurement medium: various liquid and liquid-solid two-phase fluids with conductivity greater than 5 μ S/cm.
3. Flow velocity range: 0.2-8m/s.
4. Work pressure: 1.6MPa.
5. Environmental temperature: -40 ℃ to+50 ℃.
6. Medium temperature: PTFE lining ≤ 180 ℃; Rubber material lining ≤ 65 ℃.
7. Explosion proof mark: Exmibd Ⅱ BT4.
8. Explosion proof certificate number: GYB01349.
9. External magnetic interference: ≤ 400A/m.
10. Shell protection: integrated type: IP65;
Detached type: Sensor IP68 (5 meters underwater, with rubber lining); Converter IP65.
11. Output signal: 4-20mA.DC, load resistance 0-750 Ω.
12. Communication output: RS485 or CAN bus.
13. Electrical connection: M20 × 1.5 internal thread, φ 10 cable hole.
14. Power supply voltage: 90-220V.AC, 24 ± 10% V.DC.
15. Power consumption: ≤ 10VA.

7、 Classified by excitation method:
To generate a uniform and constant magnetic field, it is necessary to choose a suitable excitation method. According to the excitation current method, there are DC excitation, AC (power frequency or other frequencies) excitation, low-frequency rectangular wave excitation, and dual frequency rectangular wave excitation.
1. DC excitation
The direct current excitation method uses direct current or magnets to generate a constant and uniform magnetic field. This type of DC excitation transmitter is minimally affected by AC electromagnetic field interference, thus the effect of self inductance in the liquid can be ignored. However, using a direct current magnetic field can easily polarize the electrolyte liquid passing through the measurement pipeline, that is, the electrolyte is electrolyzed in an electric field, producing positive and negative ions. Under the action of the electric field force, negative ions run towards the positive electrode and positive ions run towards the negative electrode, which will cause the positive and negative electrodes to be surrounded by ions of opposite polarity, seriously affecting the normal operation of the instrument. Therefore, DC excitation is generally only used to measure non electrolyte liquids, such as liquid metal flow rates (at room temperature and at high temperatures for liquid steel, lithium, potassium), etc.
2. Communication excitation
In industry, most of them use power frequency (50Hz) AC excitation to generate alternating magnetic fields, avoiding polarization interference on the surface of DC excitation electrodes. However, using AC excitation can bring a series of electromagnetic interference problems (such as orthogonal interference, in-phase interference, zero drift, etc.). Nowadays, AC excitation is being replaced by low-frequency square wave excitation.
3. Low frequency square wave excitation
There are two types of low-frequency square wave excitation waveforms: binary (positive negative) and ternary (positive zero negative zero), with frequencies typically ranging from 1/2 to 1/32 of the power frequency. Low frequency square wave excitation can avoid orthogonal electromagnetic interference caused by AC magnetic fields, eliminate power frequency interference caused by distributed capacitance, suppress eddy currents caused by AC magnetic fields on pipe walls and inside fluids, and eliminate polarization phenomena caused by DC excitation.

8、 Troubleshooting:
During operation, various faults may cause inaccurate measurements. Generally, faults that occur during operation can be divided into two categories. One type is caused by the malfunction of the flowmeter itself or damage to its components; One type of fault is caused by changes in external conditions, such as unstable output, countless flows, excessive errors, etc. Here are several simple troubleshooting methods:
a、 Unstable output: 1. Unstable flow field; 2. The liquid detected by the sensor contains gas and large solid blocks; 3. Electrical connection virtual connection; 4. Poor grounding; 5. Solution to electrode leakage: 1. Modify the pipeline or install fake sensors; 2. Normal phenomena; 3. Check the wiring and connect the wires properly; 4. Connect the ground wire properly; 5. Repair the sensor.
b、 Liquid flow without output: 1. Reverse the two core wires of the signal transmission cable between the converter and the liquid flow; 2. The power supply is not connected or has poor contact; 3. There is leakage in the sensor instrument pipeline, housing, and end face. Solution: 1. Reverse the wire head; 2. Connect the power supply and maintain good contact; 3. Repair the sensor.
c、 Liquid does not flow but has output: 1. There is a broken circuit in the signal transmission cable connection between the converter and the liquid; 2. The signal cable is disconnected from the electrode connection; 3. Surface contamination or deposition of insulation layer on the electrode; 4. Poor grounding or open circuit. Solution: 1. Connect the cable properly; 2. Open the sensor and reconnect it; 3. Clean the surface of the electrode; 4. Connect the ground wire properly.
d、 Excessive error: 1. Zero point too high; 2. Not filled with liquid; 3. Excessive distortion of the power supply; 4. Poor grounding. Solution: 1. Adjust the zero point again; 2. Improve pipeline conditions, with sensors always filled with liquid; 3. Improve the power supply conditions to meet normal working conditions; 4. Connect the ground wire properly.

9Installation requirements:
Selection of installation environment
1. Try to stay away from equipment with strong electromagnetic fields as much as possible. Such as large motors, large transformers, etc.
2. The installation site should not have strong vibrations and the ambient temperature should not change significantly.
3. A place that is convenient for installation and maintenance.
Selection of installation location
1. The flow direction indicator on the sensor must be consistent with the direction of the measured medium flow in the pipeline.
2. The installation position must ensure that the measuring tube is filled with the measured medium.
3. Choose a location with smaller fluid flow impulse, which should be away from the pump and local resistance components (valves, elbows, etc.)
4. When measuring two-phase fluids, a location that is not prone to phase separation should be selected.
5. Installation in areas with negative pressure inside the pipe should be avoided as much as possible.
6. When the measured medium easily causes adhesion and scaling on the inner wall of the electrode and measuring tube, it is recommended that the flow velocity inside the measuring tube should not be less than 2m/s.
At this point, a tapered pipe slightly smaller than the process diameter can be used. To clean electrodes and measuring tubes without interrupting flow in the process pipeline, sensors can be installed in parallel with cleaning ports.
Selection of installation location
In order to ensure stable operation of the transmitter, the following requirements should be noted when selecting the installation location:
1. Try to avoid ferromagnetic objects and specific equipment with strong electromagnetic fields (such as large motors, transformers, etc.) to prevent the magnetic field from affecting the working magnetic field and flow information of the sensor.
2. It should be installed in a dry and ventilated place as much as possible, and should not be installed in damp or water prone areas.
3. Avoid direct sunlight and rain as much as possible, and avoid environments with temperatures above 45 ℃ and relative humidity above 95.9%.
4. Choose a place that is easy to maintain and has convenient activities.
5. The flowmeter should be installed at the rear end of the water pump and must not be installed on the suction side; The valve should be installed on the downstream side of the flowmeter.

10、 Installation precautions:
1. When transporting and lifting sensors, the sling should be placed at the neck position next to the flanges at both ends of the sensor. Do not insert the pipe support into the measuring or pipe for lifting to avoid damaging the lining.
2. Before installation, carefully wipe the electrode surface inside the sensor with alcohol cotton to remove any oily contaminants caused by hand touch or other reasons.
3. The inner diameter of the sealing gasket during installation should be consistent with the inner diameter of the measuring tube lining.
4. It is necessary to ensure that the junction box is dry, otherwise the instrument may produce measurement errors. 9、 Installation precautions.
1. The axis of the non measuring electrode must be approximately horizontal;
2. The measuring pipeline must be filled with liquid;
3. There should be a straight pipe section with a length of 5 * D (D is the inner diameter of the flow meter) in front of the flow meter, and at least a straight pipe section with a length of 3 * D (D is the inner diameter of the flow meter) behind it;
4. The flow direction of the fluid is consistent with the arrow direction of the flowmeter;
5. Vacuum inside the pipeline can damage the lining of the flowmeter, so special attention should be paid;
6. There should be no strong electromagnetic field near the flowmeter;
7. There should be ample space near the flowmeter for installation and maintenance;
8. If there is vibration in the measuring pipeline, there should be fixed supports on both sides of the flowmeter. When measuring mixed liquids of different media, the distance between the mixing point and the flowmeter should be at least 30 × D (D is the inner diameter of the flowmeter). To facilitate the cleaning and maintenance of the flowmeter in the future, a bypass pipeline should be installed.
11、 When grounding protection, the following points should be noted:
1. Sensors and converters should be grounded separately and not connected to motors or process pipelines. The grounding resistance should be less than 10 ohms.
2. The measuring tube, housing, shielding wire, converter, and secondary instrument of the sensor must be grounded.
3. The grounding of sensors and converters should be done on site, and the shielding layer of secondary instruments should be grounded on the control room side. Do not connect multiple terminals to avoid interference caused by different potentials.
4. The sensor is installed on a metal pipeline, and the grounding wire of the sensor can be connected to the pipeline flange according to the manufacturer's requirements to form a reliable grounding circuit. The grounding point of the instrument should be an independent grounding point and cannot be shared with other electrical equipment.

12、 Preparation before operation:
1. Before officially putting into operation after installing the wiring, the installation and wiring should be checked again for correctness. (For split body types)
2. Open the valve before the bed dries up and close the valve after the sensor, allowing the sensor to be filled with the measured medium.
3. After the preparation work is completed, first open the upstream valve of the sensor, then slowly open the downstream valve, and observe that the instantaneous flow display of the converter should change towards the large direction, indicating that the direction of the signal line is correct. Otherwise, swap the wiring positions of signal lines A and B. (For split body types)
4. Open the front and rear valves of the sensor, drain the liquid for a few minutes, and release the gas inside the pipe.
5. Close the downstream valve of the sensor and then close the upstream valve to fill the sensor with the measured medium. Then make matching adjustments. Please refer to the converter manual for the zero adjustment and instrument coefficient setting of the sensor and converter.

13、 Main technical data:

1. Technical data of the whole machine and sensors:

2. Converter technology data:

3. Selection of lining:

4. Selection of imported protective flanges and grounding flanges (or grounding rings):

5. Selection of electrodes:

14、 Correct selection:

The selection of instruments is a very important task in instrument applications. Relevant data shows that 2/3 of instrument failures in practical applications are caused by incorrect selection or installation of instruments. Please pay special attention.

1. Collect data:

The composition of the fluid being tested;
High traffic, low traffic;
High work pressure;
Z high temperature, Z low temperature;

2. Range confirmation:

The flow rate of the measured medium in general industrial flow meters should be between 2-4m/s. In special cases, the low flow rate should not be less than 0.2m/s, and the high flow rate should not exceed 8m/s. If the medium contains solid particles, the commonly used flow rate should be less than 3m/s to prevent excessive friction between the lining and the electrode; For viscous fluids, the flow velocity can be chosen to be greater than 2m/s. A higher flow velocity helps to automatically eliminate the effect of viscous substances attached to the electrode, which is beneficial for improving measurement accuracy.

Under the condition that the range Q has been determined, the size of the flowmeter diameter D can be determined based on the range of flow velocity V mentioned above, and its value can be calculated by the following formula:

Q=πD2V/4
Q: Flow rate (㎡/h) D: Inner diameter of pipeline V: Flow rate (m/h)

The range Q of the flowmeter should be greater than the expected flow rate value, and the normal flow rate value should be slightly greater than 50 of the flowmeter's full range scale.

3Reference flow range:

4. Selection code: