Abstract: the optimization of plug-in electromagnetic flowmeter
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In recent years, with the development of flow metering industry, electromagnetic flow meter with no moving parts, no pressure loss, the advantages of wide measuring range is applied to various occasions, and in the use process encountered a big traffic problem is how to improve the large diameter.
More flow meter manufacturers choose model price quote you are welcome to inquire, here is to optimize plug-in electromagnetic flowmeter research paper details the linearity of the scale.
In recent years, with the development of flow metering industry, electromagnetic flow meter with no moving parts, no pressure loss, the advantages of wide measuring range is applied to various occasions, and in the use process encountered a difficult problem is how to improve the accuracy of big caliber flow metering.
If you use the pipeline electromagnetic flowmeter measurement of large diameter pipeline flow, is their large size and high processing cost and calibration and installation and maintenance are very difficult, caused a lot of inconvenience for the engineering application.
So in this case, the general use plug-in electromagnetic flowmeter instead of electromagnetic flow meter used to measure large diameter pipeline pipe flow.
But plug-in electromagnetic flowmeter can produce nonlinear phenomenon, affect the accuracy of measurement.
Now many scholars to solve this problem more USES is more linear compensation method, the inside of the scope of the whole range flow into multiple flow section, and to solve the flow coefficient of different stages respectively, which can be concluded that paragraphs flow value.
But this method is to use more complex, and also is limited by the precision.
So this article embarks from the structure of electromagnetic flowmeter itself, find out the causes of nonlinear phenomena, and find out from the source method to improve linearity plug-in electromagnetic flowmeter.
Working principle of the 2 plug-in electromagnetic flowmeter plug-in electromagnetic flowmeter measurement principle is based on Faraday's law of electromagnetic induction (
Among them, the E to produce inductive electromotive force between two electrodes, B for the magnetic induction intensity, L is the length of cutting magnetic induction line, 珋 v as the average flow velocity, liquid as conductive medium, schematic diagram is shown in figure 1.
Figure 1 plug-in electromagnetic flowmeter principle diagram and (
The transformation can be represented as (
When B and L is constant, as long as the measured induction electromotive force E get average flow velocity, due to the cross-sectional area of the measured pipe is known, so that you can easily get a conductive liquid volume flow (
Among them, the measured pipe diameter, D for Qv for volume flow.
Type, when must be inserted into the pipe structure, volume flow Qv is proportional to the ratio of E/B, and the temperature of the fluid pressure, density, tube, etc.
When the magnetic induction intensity B is constant, the volume flow rate Qv is proportional to the induced electromotive force E, namely the volume flow and has a linear relation between the induction electromotive force is completely.
3 sensor linearity to assess linearity is one of the main static performance index, defined as the output of the test system and input system can maintain normal proportion relations as ideal system (
Linearity reflects the degree of the straight line with a certain rules of calibration curve, the line is in a certain way to determine the ideal straight line.
Called linearity and nonlinearity, reference GB/T18459-2001 in the main static performance indicators calculation method, the sensor linearity definition: positive, revesal actual average characteristic curve relative to the reference line (
Zui large deviation, expressed as a percentage with full range of output.
This metric is usually expressed as a linear error (
Among them, & Delta;
Max residual, yF.
S for the theory of full scale output.
This article zui small squares method is adopted to improve the linearity, namely the zui small squares linear fitting line.
Zui small squares line to ensure the sensor actual output the average of the sum of the squares of the deviation of it for the small zui, fitting line could be the result and the deviation between the measured results is, more reliability.
Linearity of calibration curve is, by definition, this article zui small degree of deviation squares fitting line.
4 plug-in electromagnetic flowmeter nonlinear phenomenon causes plug-in electromagnetic flowmeter in the pipeline to be tested when using appropriate location punch insert to measure conductive fluid flow, and can in the case of continuous flow out for cleaning and maintenance, the operation is very convenient.
But probe insert pipe for pipeline flow field, the equivalent of introduced a choke devices, probe for the fluid motion, as shown in figure 2.
Figure 2 fluid flow around the probe around the probe of fluid flow, but because of the viscous force, will form the boundary layer on the probe surface.
Along with the fluid flow around up and down the surface, boundary layer thickness increasing.
The more close to the wall, the change of the flow field in the more complex.
And the change of the flow field distribution can expand the measured average flow velocity and the error between the actual flow velocity.
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