1. When the direction, diameter and opening of the valve change, eddy current and flow field distortion will be generated, which will affect the measurement of the sensor electrode and thus affect the accuracy of the instrument. So as far as possible to leave the elbow, hand valve, regulating valve and other parts of a certain distance.
2. Ensure the verticality between the fluid and the sensor magnetic field. Pay attention to the vertical direction of the pressure tube when welding the pressure tube when installing the pressure tube in the pipeline. And the extension line connected by the flange short pipe passes vertically through the center of the cross section of the pipe, which can ensure that the fluid is perpendicular to the magnetic field.
3. Avoid interference sources. To ensure measurement accuracy, avoid installing sensors in places where vacuum, gas, and eddy currents are likely to occur. The communication cable between the sensor and the intelligent transmitter should avoid the motor and other strong electric equipment.
The measuring principle of the plug-in electromagnetic flowmeter is based on Faraday's law of electromagnetic induction. The measuring tube of the flowmeter is a short tube of non - conductive alloy lined with insulating material. Two electrodes are fixed on the measuring tube through the wall along the diameter of the tube. The electrode head is basically flush with the inner surface of the lining. When the excitation coil is pulsed by two waves, a working magnetic field with flux density of B will be generated in the direction perpendicular to the axis of the measuring tube. At this point, if a fluid with a certain conductivity passes through the measuring tube. The cut magnetic line of force is induced into the electromotive force E. The electromotive force E is proportional to the product of the magnetic flux density B, the inner diameter of the measuring tube d, and the average velocity v. The electromotive force E(flow signal) is detected by the electrode and sent to the converter through the cable. Converter will flow signal amplification processing, can display fluid flow, and output pulse, analog current signal, for flow control and regulation. Although the plug-in electromagnetic flowmeter is simple to operate and less maintenance, it will still make the electrode dirty or worn for a long time. Therefore, in order to ensure the accuracy of measurement, it is very necessary to overhaul the plug-in electromagnetic flowmeter regularly. For plug-in electromagnetic flowmeters, the system must be shut down for each maintenance to drain the fluid in the pipe before it can be dismantled. If a fault occurs during abnormal maintenance, the disassembly and installation of the plug-in electromagnetic flowmeter can greatly affect the efficiency of continuous production. Therefore, an isolated ball valve can be installed on the mounting seat to realize on-line insertion and removal when the system is not shut down to ensure the continuous and stable operation of the system.
