Introduction of electromagnetic flowmeter

Electromagnetic flowmeter is a flow measurement instrument based on Faraday's electromagnetic induction principle, which is widely used in flow measurement of liquid and conductive fluids. Its working principle can be briefly summarized as the following steps:

1. Faraday electromagnetic induction principle
The working principle of electromagnetic flowmeter is based on Faraday's law of electromagnetic induction, which describes that when a conductive fluid flows through a magnetic field, an electromotive force (i.e., voltage) is generated in the fluid. The magnitude of this electromotive force is proportional to the flow rate.

Specifically, when the fluid passes through the magnetic field located in the flowmeter pipeline, the charged particles in the fluid (such as ions in water) will move under the action of the magnetic field and generate an electromotive force (voltage) in a direction perpendicular to the magnetic field and the flow rate. This electromotive force is proportional to the flow rate of the fluid.

2. Structural composition
The electromagnetic flowmeter is mainly composed of the following parts:

- **Sensor**: It includes a measuring tube and a magnet. The fluid passing through the measuring tube generates an electromotive force by interacting with the magnetic field.

- **Electrode**: The electrode picks up the electromotive force signal by contacting the fluid. Usually, the electrode is installed on the inner wall of the measuring tube, perpendicular to the direction of fluid flow.
- **Signal converter**: Convert the electromotive force signal received by the electrode into a flow signal, and display and process it.

3. Flow measurement process
- **Magnetic field effect**: When the fluid passes through the measuring tube of the electromagnetic flowmeter, the built-in magnet generates a magnetic field perpendicular to the flow direction.
- **Electromotive force generation**: When charged particles (such as ions) in the fluid move in the magnetic field, an electromotive force is induced in the fluid according to Faraday's law. The magnitude of the electromotive force is proportional to the flow rate.
- **Signal acquisition**: The electromotive force of the fluid in the magnetic field is captured by the electrode, and the voltage difference between the electrode and the fluid reflects the flow rate.
- **Signal processing and flow calculation**: By processing the electromotive force signal, the converter can calculate the actual flow value of the fluid.

4. Advantages and applications
- **No mechanical parts**: The electromagnetic flowmeter has no mechanical parts, so there is no wear and tear, and the maintenance cost is low.
- **Applicable to conductive fluids**: The electromagnetic flowmeter is suitable for flow measurement of various conductive fluids, such as water, sewage, acid and alkali solutions, slurry, etc.
- **Not affected by factors such as fluid density, viscosity, temperature, etc.**: The measurement results are independent of the physical properties of the fluid and have high accuracy.

5. Application scenarios
- Water treatment, chemical processes, food and beverages, medicine, slurry, oil and gas, etc., especially when measuring corrosive or viscous fluids.

It should be noted that electromagnetic flowmeters cannot be used for non-conductive fluids (such as gas, oil fluids) or liquids without charged particles in the fluid.

Selection knowledge of electromagnetic flowmeter
The selection of electromagnetic flowmeter needs to be comprehensively considered based on multiple factors to ensure that the instrument can accurately and stably measure the flow rate. The following are several key factors to consider when selecting an electromagnetic flowmeter:

1. **Fluid type**
- **Conductivity requirements**: Electromagnetic flowmeters can only be used to measure conductive fluids, such as water, sewage, acid and alkali solutions, slurries, etc. When selecting, it is necessary to confirm whether the fluid has sufficient conductivity. For low-conductivity fluids, it may be necessary to consider improving the electrode material or installing an enhanced sensor.
- **Fluid properties**: The corrosiveness, viscosity, temperature, pressure and other physical and chemical properties of the fluid directly affect the service life and accuracy of the electromagnetic flowmeter. Therefore, when selecting, special attention should be paid to the pH of the fluid, whether it contains particulate matter, whether it is highly corrosive, etc.

2. **Pipeline size and flow range**
- **Pipeline diameter**: The measurement pipeline size of the electromagnetic flowmeter is usually selected based on the actual pipeline diameter. Common pipeline sizes range from a few millimeters to a few meters. The appropriate flowmeter model should be selected based on the inner diameter and flow range of the pipeline.
- **Flow range**: The range of the electromagnetic flowmeter is usually between its maximum flow rate and minimum flow rate, which needs to be determined according to the actual working conditions. When selecting, make sure that the range of the flowmeter covers the expected flow fluctuation range.

3. **Electrode material**
- The electrode material needs to be selected according to the corrosiveness, temperature, pressure and other conditions of the fluid. Common electrode materials include:
- **Stainless steel**: Suitable for most liquids, but not suitable for highly corrosive fluids such as strong acids and alkalis.
- **Titanium alloy**: Suitable for highly corrosive liquids, but the cost is relatively high.
- **Hastelloy**: Suitable for corrosive liquids such as strong acids and alkalis.
- **Platinum**: Commonly used for flow measurement with high precision requirements or special requirements.
- **Electrode surface treatment**: When there are particles in the fluid, the surface treatment of the electrode is also very important. You can choose an anti-wear surface treatment method, such as tungsten alloy coating.

4. **Signal output and communication method**
- **Analog output**: Common analog output methods of electromagnetic flowmeters include 4-20mA, voltage output, etc. 4-20mA is the most common output form, which can be easily connected to DCS and PLC systems.
- **Digital communication**: Such as HART protocol, Modbus, Profibus, etc., suitable for occasions requiring remote data transmission, monitoring and automatic control.
- **Output accuracy**: When selecting, you need to pay attention to the accuracy and resolution of the signal to ensure that the accuracy requirements of the flow control system are met.

5. **Working pressure and temperature**
- The working pressure and temperature range of the electromagnetic flowmeter are important considerations when selecting. Different flowmeter designs withstand different pressure and temperature ranges, so it is necessary to ensure that the selected flowmeter can be used normally under actual working conditions.
- Especially when working under extreme conditions such as high temperature, high pressure or low temperature, it may be necessary to select a special flowmeter.

6. **Installation environment**
- **Pipeline installation**: The electromagnetic flowmeter can be installed horizontally, vertically or diagonally, but the flow of the fluid must be smooth. Gas blockage or flow dead corners should be avoided during installation.
- **Environmental factors**: If the flowmeter is installed outdoors or in a harsh environment, you may need to select a model with a higher protection level (such as IP65 or IP68) to prevent the external environment from affecting the equipment.
7. **Is there gas or solid particles in the pipeline**
- The electromagnetic flowmeter requires that the fluid must be a continuous conductive fluid, so there must be no gas or solid particles in the pipeline. If there are bubbles or solid particles in the fluid, it may affect the measurement accuracy of the electromagnetic flowmeter.
- If the fluid contains gas, you may need to install a bubble separation device, or select a flowmeter suitable for measuring gas-containing fluids.
8. **Explosion-proof requirements**
- For flammable and explosive environments, it is necessary to confirm whether the electromagnetic flowmeter meets the relevant explosion-proof standards (such as Ex certification) when selecting. When used in such environments, explosion-proof electromagnetic flowmeters are essential.
9. **Fluid flow rate and stability**
- The accuracy of the electromagnetic flowmeter is most reliable under conditions of stable flow rate. If the flow rate of the fluid fluctuates greatly, you may need to select a flowmeter with higher accuracy and a wider measurement range, or improve the flow state by adding a straight pipe section.
10. **Accuracy requirements**
- Electromagnetic flowmeters are usually more accurate, usually ranging from ±0.5% to ±1%. Depending on actual needs, the required accuracy requirements should be determined when selecting. For applications with higher accuracy requirements (such as metering, batching, etc.), you may need to choose a high-precision model.
11. **Price and budget**
- The price of electromagnetic flowmeters is relatively high, and you need to make a reasonable choice based on the project budget when selecting. For simpler applications, you can choose a basic model; for applications that require high accuracy, high pressure resistance, or use in special environments, you may need to choose a high-end model.
12. **Brand and after-sales service**
- Different brands of electromagnetic flowmeters differ in performance, quality, and after-sales service. Choosing a brand with a good reputation and perfect after-sales service can ensure the long-term and stable operation of the equipment.
Selection summary
In summary, the selection of electromagnetic flowmeters should take into account multiple factors such as fluid characteristics, pipe size, flow range, electrode material, working conditions, and signal output method. Through accurate demand analysis, the most suitable electromagnetic flowmeter model can be selected to ensure the accuracy and reliability of flow measurement.

Pulse Output
Two types of pulse output are available to choose from: frequency output mode and pulse output mode. The meter outputs continuous square wave pulse under frequency mode, while pulse series under pulse mode. Frequency output is usually used for flow rate measurement and short period of time totalization. Pulse output can be connected to an external counter directly and is often used for long period of time totalization.
As mentioned hereinbefore, transistor open collector circuit is used for frequency and pulse output. Therefore, the external DC power supply and load are necessary.

Features
1. Measurement is not affected by the variation of flow density, viscosity, temperature, pressure and conductivity. High accuracy measurement is guaranteed according to the linear measurement principle.
2. No obstacle in the pipe, no pressure-loss and lower requirement for straight pipeline.
3. DN 6 to DN2000 covers a wide range of pipe size. A variety of liners and electrodes are available to satisfy different flow characteristic.
4. Programmable low frequency square wave field excitation, improving measurement stability and reducing power consumption.
5. Implementing 16 bits MCU, providing high integration and accuracy; Full-digital processing, high noise resistance and reliable measurement; Flow measurement range up to 1500:1.
6. High definition LCD display with backlight.
7. RS485 or RS232 interface supports digital communication.
8. Intelligent empty pipe detection and electrodes resistance measurement diagnosing empty pipe and electrodes contamination accurately.
9. SMD component and surface mount technology (SMT) are implemented to improve the reliability.

Main Applications

TQMF electromagnetic flowmeter can be used to measure the volume flow of conductive fluid in a closed pipeline. It is widely applied in the flow measurement and control in the fields of chemical and petroleum industry, metallurgy industry, water and waste water, agriculture and irrigation, paper making, food and beverage industry and pharmaceutical industry. 1.3Ambient Conditions Ambient temperature: sensor: -25℃ to + 60℃; converter: -25℃ to + 60℃. Relative humidity: 5% to 90%; 1.4Working Conditions Maximum fluid temperature: Compact type: 60℃ Remote type: Teflon 150℃ Neoprene 80℃; 120℃ Polyurethane 70℃ Fluid conductivity: ≥ 5S/cm

Converter Circuit Schematic

The converters supplies a stable exciting current to the coil in the sensor of electronetic flowmeters to get B constant and amplifies the electromotive force and convert it into standard signals of current or frequency so that the signals can be used for displaying, controlling and processing. The schematic of converter circuit is shown in Fig. 2.1.

Table of Parameter Setting Menu

The converter setting menu consists of 45 items. Many of them are set up by manufacturer before shipping. It is not necessary to change them when applying. There are only a few of them to be set by user according to the application. The menu items are listed in the table below:

Scenario application:

FAQ
1. Q: What information need to be provided to choose the suitable model?
A: Application field, Nominal pressure ,Medium & medium temperture , Power supply , Output,
Flow range, Accuracy, Connection and other parameters.
2. Q: Are you a trade company or a manufacturer?
A: We are an ISO approved manufacturer specialized in level and flow measuring instruments.
OEM & ODM service are available. Welcome to visit us in China.
3. Q: What is your MOQ?
A: To start our cooperation, sample order is acceptable.
4. Q: What is your delivery date for the Intelligent Mini Micro Turbine Fuel Oil Diesel Flow Meter?
A: The delivery date is about 3-15 working days after receipt of payment.
5. Q: What is your payment terms?
A: We support T/T, PayPal ,Western Union.
For mass production order, it is 30% deposit in advance and 70% balance before shipment.
6. Q: Do you have a warranty for the Flow Meter?
A: Yes, we have the warranty of 12 months.