Customizable electromagnetic flow meter, electronic digital display flow meter, pipeline integrated digital display flow meter

Shenzhen Volcker is mainly engaged in the design/installation and technical development services of instruments and meters in the fields of fluid measurement and process control. At present, the company's main products include flow switches, pressure switches, temperature switches, electromagnetic flow meters, vortex flow meters, turbine flow meters, ultrasonic flow meters, level flow meters, and other instruments. Application industries: petrochemical, natural gas, machinery, electricity, metallurgy, building materials, food and pharmaceutical manufacturing, agriculture, environmental protection, and other fields. Our company can customize instrument specifications according to the special requirements of users and on-site conditions, and provide installation and debugging services

Knowledge extension:

The working principle and composition of electromagnetic flow meters

Electromagnetic flow meter

1. Working principle

The measurement principle of electromagnetic flow meter is shown in Figure 1. According to Faraday's law of induction, the flow of conductive liquid in the magnetic field will produce electromotive force E, which is proportional to Magnetic flux density B and the average flow velocity of conductive liquid v: E=KBDv

In the formula: E - the electromotive force V generated by the conductive fluid in the magnetic field;

K -- proportional coefficient, in the pipeline inner diameter D and Magnetic flux density

When B remains constant, K is a constant of 1;

B -- Magnetic flux density T;

D - inner diameter of the measuring tube m;

V - Average flow velocity of conductive liquid in m/s.

The electromagnetic flowmeter uses the above functional relationship to derive v=E/(KBD). The actual measured liquid flow rate is v, and then the flow rate of the conductive fluid medium is calculated by the volume flow rate QV=π D2 v/4 of the measured medium.

Figure 1

2. Composition of measuring system

The electromagnetic flowmeter mainly consists of two parts: a flow sensor and a signal transmitter, as shown in Figure 2. The excitation coil on the sensor receives the excitation current transmitted by the transmitter to generate a magnetic field and outputs an induced electromotive force signal; The signal transmitter converts the induced electromotive force signal into a flow signal or an analog signal and sends it to the control system. Electromagnetic flow meters are divided into integrated and split types according to their composition.

Another important condition for stable operation of electromagnetic flow meters is grounding. When the fluid flows through a magnetic field, using the conductive fluid itself as a reference potential, a positive potential is generated on one side of the measuring tube electrode and a negative potential is generated on the other side, forming a potential difference. But this electromotive force signal is usually only a few millivolts and is susceptible to external interference. To prevent interference, the reference potential is connected to the ground as the zero potential, ensuring that the sensor outputs a precise and stable signal. The grounding terminal of the sensor and converter must be at the same potential as the measured medium in order to form a symmetrical input and output circuit.

Figure 2

3. System characteristics

The main characteristics of electromagnetic flow meters are as follows: ① Unlike differential pressure and volumetric flow meters, electromagnetic flow meters measure pipes without flow blocking components and have minimal pressure loss, making them suitable for large-diameter pipelines; ② Not affected by changes in temperature, pressure, density, and viscosity parameters of the measuring medium, no correction or compensation is required, only the conductivity of the measuring medium is required σ＞ five μ S/cm; ③ Wide range ratio, linear relationship between output signal and flow rate; ④ High measurement accuracy, up to ± (0.1%~0.5%); ⑤ The installation requirements are low, and the requirements for the front and rear straight pipe sections are low. Generally, it is sufficient to meet the requirements for the front straight pipe diameter D to be ≥ 5D, and the rear straight pipe diameter D to be ≥ 2D; ⑥ High, suitable selection of lining and electrode materials can measure the flow rate of various corrosive media. It should be noted that electromagnetic flow meters cannot measure the flow rate of non-conductive media, nor are they suitable for measuring media containing gases, which can cause significant fluctuations in measurement data.