An electromagnetic flowmeter is a flow measurement instrument based on Faraday's law of electromagnetic induction. It is mainly used to measure the flow of conductive liquids.
Its working principle is: when a conductive liquid moves in a magnetic field, it cuts the magnetic lines of force, thereby generating an induced electromotive force in the conductive liquid. The magnitude of the induced electromotive force is related to the flow rate of the conductive liquid, the magnetic field strength and the inner diameter of the measuring tube.
The electromagnetic flowmeter consists of an electromagnetic sensor, a converter and a display instrument. Among them, the electromagnetic sensor is the core component of the electromagnetic flowmeter, which includes a measuring tube, a magnetic circuit system, electrodes and other parts. The converter converts the electrical signal output by the sensor into a standard electrical signal output, usually a 4-20mA current signal or a 0-10V voltage signal. The display instrument is used to display parameters such as flow rate and cumulative flow.
Electromagnetic flowmeters have the advantages of high measurement accuracy, wide range, no pressure loss, and a wide range of applications. They are widely used in flow measurement in industries such as petroleum, chemical, metallurgy, papermaking, and food.
When selecting an electromagnetic flowmeter, you need to consider factors such as the corrosiveness, temperature, pressure, and flow rate of the measured medium, and select the appropriate material, caliber, and model according to the actual situation.
How to select an electromagnetic flowmeter
The electromagnetic flowmeter is a commonly used flow measurement instrument that works based on Faraday's law of electromagnetic induction and is mainly used to measure the flow of conductive liquids. When selecting, the following factors need to be considered:
1. Measuring medium: The electromagnetic flowmeter can only measure conductive liquids, so it is necessary to determine the conductivity of the measured medium. Generally speaking, liquids with a conductivity greater than 5μS/cm can be measured using an electromagnetic flowmeter.
2. Measuring range: Select a suitable flowmeter caliber according to the actual flow range. The electromagnetic flowmeter caliber should be slightly larger than the actual pipeline caliber to ensure measurement accuracy and stability.
3. Accuracy requirements: Select the appropriate accuracy level according to the measurement requirements. The accuracy of the electromagnetic flowmeter is usually 0.5%~1.0%, and the high-precision type can reach 0.2%.
4. Pressure level: Select the appropriate flowmeter pressure level according to the working pressure of the pipeline system. Generally, a flowmeter with a pressure higher than the actual working pressure should be selected to ensure safety and reliability.
5. Lining material: The sensor of the electromagnetic flowmeter needs to be in direct contact with the measured medium, so it is necessary to select a suitable lining material to prevent corrosion and wear. Common lining materials include PTFE, PFA, polyurethane, etc.
6. Electrode material: Select a suitable electrode material according to the corrosiveness of the measured medium. Common electrode materials include stainless steel, Hastelloy, titanium, tantalum, etc.
7. Output signal: The electromagnetic flowmeter can output analog signals (4-20mA, 0-10V, etc.) or digital signals (RS485, Modbus, etc.). Select the appropriate output signal type according to actual needs.
8. Protection level: Select the appropriate protection level according to the requirements of the installation environment. Generally, IP65 or higher protection level should be selected to ensure that the electromagnetic flowmeter works normally in harsh environments.
9. Installation method: The electromagnetic flowmeter has a variety of installation methods such as flange connection, threaded connection, and clamp connection. Select the appropriate installation method according to the pipeline connection method.
10. Price and after-sales service: Under the premise of meeting the measurement requirements, choose products with high cost performance and consider the manufacturer's after-sales service capabilities. Understand the product performance and characteristics to ensure that the selected electromagnetic flowmeter can meet the actual application needs.