Views: 4 Author: Site Editor Publish Time: 2020-05-29 Origin: Site
The electromagnetic flowmeter is mainly composed of two parts: flow sensor and signal transmitter. 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. Send it to the control system. Electromagnetic flowmeter is divided into one type and split type according to the composition.
Another important condition for the stable operation of the electromagnetic flowmeter is grounding. When a fluid flows through a magnetic field, the conductive fluid itself serves as a reference potential. A positive potential is generated on one side of the measuring tube, and a negative potential is generated on the other side, forming a potential difference. However, the electromotive force signal is usually only a few millivolts, which is susceptible to external interference. To prevent interference, the reference potential is grounded as a zero potential to ensure that the sensor outputs an accurate and stable signal. The ground terminals of the sensor and converter must have the same potential as the measured medium to form a symmetrical input and output circuit.
The main characteristics of the electromagnetic flowmeter are as follows: ① Unlike the differential pressure flowmeter and the volumetric flowmeter, the electromagnetic flowmeter has no obstacles in the measuring tube and the pressure loss is very small. Suitable for large diameter pipes. ②Not affected by the temperature, pressure and pressure of the measuring medium. The effect of changes in density and viscosity parameters does not need to be corrected and compensated, only the conductivity of the measurement medium σ> 5μS / cm. ③The range ratio is large, and the output signal has a linear relationship with the flow rate. ④High measurement accuracy, can reach ± (0.1% ~ 0.5%). ⑤ Low installation requirements, low requirements for front and rear straight pipe sections, generally meet the diameter D of the front straight pipe section ≥ 5D, and the diameter D of the rear straight pipe section ≥ 2D is sufficient. ⑥High cost performance and wide application range. The reasonable choice of lining material and electrode material can measure the flow of various corrosive media. It should be noted that the electromagnetic flowmeter cannot measure the flow rate of non-conductive media, nor is it suitable for measuring gas-containing media, which will cause large fluctuations in the measurement data.