Thread Content
Electromagnetic flowmeters have some specific requirements for their components, as follows: ① Measurement tube The magnetic field must pass through the wall of the tube to reach the fluid. Here, the measurement pipeline is only allowed to be made of non-magnetic materials. The voltage induced in the fluid being measured must not allow for a short circuit with the conductive pipe walls; therefore, the pipeline must be made of insulating material, or an insulating lining must be applied to the inner wall of the non-magnetic metal pipe (the part of the pipe wall that comes into contact with the fluid). The lining material must possess sufficient corrosion resistance. ②Measurement electrodes: The measurement electrodes of electromagnetic flowmeters come into direct contact with the fluid being measured. Therefore, the materials used must also have sufficient corrosion resistance and ensure good electrical conductivity when in contact with the fluid being measured. The most commonly used electrode materials are stainless steel and chromium-nickel alloys; followed by platinum, aluminum, titanium, and zirconium metals. In electromagnetic flowmeters with ceramic measurement tubes, electrodes made from a mixture of ceramic and metal materials are used. Additionally, the new electrode structure is easy to replace. The choice of the measuring electrode material determines the measurement performance of the electromagnetic flowmeter. For fluids with extremely low electrical conductivity or insulating deposits on the pipe walls that impair electrical conduction, this can affect the proper progress of measurements. In such cases, an electromagnetic flowmeter that uses capacitive coupling to generate induced voltage signals can be employed; this type of meter features a set of large-area capacitive plates installed inside a lined or non-conductive pipe. ③Excitation coil: The excitation coil is installed on the pipeline perpendicular to the electrode shaft; it is powered by a current supplied by the transmitter, and generates a square-wave magnetic field. The magnetic field pattern (the distribution of magnetic field strength and space within the measurement pipeline) is affected by the linearity of the electromagnetic flowmeter’s display and the velocity profile; the excitation coil is protected by the electromagnetic flowmeter’s housing. ④Conversion transmitter: The main task of the conversion transmitter for electromagnetic flowmeters is to convert the induced voltage signal E into a standard current signal of 4–20 mA. The induced voltage signal is only in the microvolt to millivolt range; therefore, the main functions of the converter/transmitter in an electromagnetic flowmeter include amplification, conversion, filtering, calibration, etc. ·Voltage signal amplification. The input amplifier of the transmitter must have a very high input impedance to prevent the internal resistance of the electrodes from affecting the measurement accuracy. ·Convert the amplified voltage signal into a digital value. ·Voltage signal filtering to eliminate interference voltages greater than 1/10 of the flow signal. ·Calibrate the corresponding operating parameters, including the nominal value of the measuring sensor, the upper limit of the measurement range, and the voltage output range in millivolts. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content! http://www.yb1518.com/UploadFiles/2012717174126829.jpg