Causes of Measurement Errors in Electromagnetic Flowmeters

Electromagnetic flowmeters, despite their high accuracy and stability. However, there are some errors in the measurement! What is the reason for this? Here's to analyze and analyze for everyone:

The liquid in the electromagnetic flowmeter tube is not full. Due to insufficient back pressure or poor installation position of the flow sensor, the liquid in the measurement tube may not be fully filled, and the phenomenon of failure may be manifested in different degrees of incompleteness and flow conditions. If a small amount of gas is stratified or wavy in the water pipe, the fault phenomenon is manifested as an increase in the error, that is, the flow measurement is inconsistent with the actual value; if the flow is a bubble flow or a plug flow, the fault phenomenon does not match the measured value and the actual value. In addition, output shaking will occur due to the gas phase covering the electrode surface instantaneously; if the gas phase portion of the flow cross-sectional area in the stratified flow of the horizontal pipe increases, that is, the degree of liquid underfill increases, output shaking will also occur if the liquid is not full. The situation is so serious that if the liquid level is below the electrode, an overfull-scale phenomenon will occur.

Electromagnetic flowmeter liquid contains a solid phase, the liquid contains powder, granules or fibers and other solids, possible failures; 1 slurry noise; 2 electrode surface contamination; 3 conductive deposition layer or insulating deposition layer covering the electrode or lining; The lining is worn or covered by sediments and the flow cross-sectional area is reduced.

Electromagnetic flowmeters may crystallize liquids. Electromagnetic flowmeters should be used with caution. Some easy-to-crystallize chemical materials can be normally measured under normal temperature conditions. Because the fluid-carrying conduits have good heat-tracing insulation, they will not work during heat preservation work. Crystallization, but the measurement tube of the electromagnetic flow sensor is difficult to implement thermal insulation, so the fluid is easy to cause a solid layer on the inner wall due to cooling when flowing through the measuring tube. Because the flow meter measurement using other principles also has crystallization problems, in the absence of other better methods, an “oring” electromagnetic flow sensor with a very short measuring tube length can be selected, and the flow meter can be selected. The upstream pipeline heat tracing insulation is strengthened. In the pipe connection method, it is convenient to disassemble and disassemble the flow sensor, and it can be easily removed and maintained once it is crystallized.

Electromagnetic flowmeter electrodes and grounding rings caused by improper material selection problems caused by the material and the measured medium does not match the electromagnetic flowmeter caused by the failure and the media contact parts of the electrode and grounding ring, matching failures in addition to corrosion problems, as long as it is Electrode surface effect. The surface effects should be: 1 chemical reaction (surface film formation, etc.); 2 electrochemical and polarization phenomena (potential generation); 3 catalytic effect (air mist generated on the surface of the electrode). Ground loops also have these effects, but the impact is less.

Electromagnetic Flowmeter