RU2303767C2 - Method of calibration and inspection of electromagnet flow meters - Google Patents

Abstract

FIELD: method is based upon imitation modeling of process of measurement of electromagnet flow meter.

SUBSTANCE: method of inspection provides for placement of multiple similar small-sized induction coils onto working area of flow meter's channel; coils are disposed uniformly to have one pitch. Voltage in any coil, which voltage is induced by magnetic field of primary converter, is subject to integration, and parameter λ1 is calculated, which parameter characterizes intensity of magnetic field onto any local surface of channel, onto which surface the corresponding small-sized induction coil is disposed. Coefficient of conversion of primary converter of electromagnet flow meter is calculated for all (n) local areas of channels on base of received values λ1 for preset distribution of flow speed in channel.

EFFECT: improved precision of calibration of electromagnet flow meters at any specified cinematic structures of flow.

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Description

The invention relates to the field of instrumentation, and in particular to a technique for measuring flow using electromagnetic flow meters, to their calibration and verification by a simulation method.

It is known that electromagnetic flowmeters are slightly sensitive to changes in the distribution of flow velocity in the channel [1]. To verify electromagnetic flowmeters with various kinematic flow structures (i.e., with different distributions of the flow velocity in the channel), a method is used based on simulation of the measurement process of an electromagnetic flowmeter.

A known imitation method of checking electromagnetic flowmeters, which provides for the conversion of the magnetic field of the primary Converter into electrical voltage using an induction coil placed in the channel; the integration of the electrical voltage obtained at the output terminals of the induction coil, and the determination of the conversion coefficient of the flow meter To _p [2].

To verify electromagnetic flowmeters with various kinematic flow structures, induction coils are used as a magnetic field transducer, the distribution of turns of which is performed according to the laws of surface weight functions corresponding to various distributions of the flow velocity in the flowmeter channel [3].

The disadvantage of the method used for checking the electromagnetic flowmeter for various distributions of the flow rate is the need to replace induction coils, because each coil corresponds to one specific distribution of flow velocity in the flowmeter channel. In addition, for large diameter flowmeters (DN 200-1000 mm or more), induction coils are bulky and complex products.

The present invention eliminates these disadvantages.

A method for checking electromagnetic flowmeters with various distributions of the flow rate involves placing in the working area on the channel surface of the electromagnetic flowmeter a plurality of (n) identical small-sized induction coils located uniformly on the channel surface with the same pitch; integration of the primary voltage transducer induced by the magnetic field in each coil and the calculation of the parameter λ _i characterizing the intensity of the magnetic field on each local surface of the channel on which the corresponding small-sized induction coil is placed, and the parameter λ _{i is} calculated by the formula:

where C _i is the integration time constant of the i-th induction coil, k _i is the ratio of the voltage obtained by integrating the output voltage of the i-th induction coil to the voltage across the resistance r included in the inductor power circuit, N _i is the total area of turns i that coil.

Based on the obtained values of the magnetic field intensity parameters for all (n) local areas of the channel surface, the conversion coefficient of the primary converter of the electromagnetic flow meter is calculated for a given distribution of the flow velocity in the channel according to the formula:

where w _i is the value of the surface weight function calculated for the i-th local surface of the channel for a given shape of the distribution of flow velocity, D is the diameter of the pipeline. Depending on the given form of the flow velocity distribution, the values of w _i change and the coefficient K _p corresponding to it is calculated.

Schemes of the device for implementing the proposed method for checking electromagnetic flowmeters with various flow structures are shown in figures 1-3. Figure 1 shows the induction coil used to implement the considered method of calibration and calibration of the electromagnetic flowmeter for various distributions of the flow rate. The coil has a flat shape, the coil turns are a spiral, the beginning and end of which are output to the output terminals. To increase its sensitivity, the turns of the coil are tightly wound (with a minimum inter-turn distance), the coil can be printed and can be multi-layered. The coil has small dimensions, its diameter is more than 1/10 of the inner diameter of the channel. Figure 2 shows the frame with many small flat induction coils 2, shows an approximate diagram of their location on the inner surface of the channel of the flow meter. For the convenience of placing coils in the channel, they are located on a cylindrical frame that is inserted into the flowmeter channel so that each coil touches its own section of the channel’s inner surface, and the axis 3 around which each coil is wound is directed perpendicular to the channel surface section on which the corresponding coil is located. The frame with coils is oriented relative to the axis of the flowmeter channel as follows: the x axis is directed along the line connecting the electrodes, the y axis is directed perpendicular to the line connecting the electrodes and the channel axis z. All axes intersect in the center of the working volume of the channel. On the frame there are two marks 1, which should coincide with the electrodes when installing the frame in the channel. Figure 3 shows a block diagram with which the proposed method is implemented. The diagram shows the primary transducer of an electromagnetic flowmeter 1, consisting of a pipe 2 with two electrodes 3 and two inductor coils for exciting a magnetic field 4. Small-sized coils in the diagram are indicated by K ₁ , K ₂ ... K _n , their outputs are connected to switch 5, programmatically controlled from a computing device 6. The low-frequency current of the inductor coils 4 is supplied from a source 7, also controlled by a calculator 6.

The operation of the device is as follows. The voltages of small coils K ₁ , K ₂ ... K _n and the voltage removed from the resistance g alternately, using switch 5 are connected to the computing device. In the computing device, all input voltages are digitized. Moreover, the voltages removed from the coils K ₁ , K ₂ ... K _n are further integrated, the parameters λ _{i of} the magnetic field intensity of the local sections of the channel surface are calculated by formula (1), and then the coefficients K _p corresponding to formula (2) are calculated different preset flow velocity distributions in the channel. The distribution of the flow velocity is set programmatically, for example, in the form of tables of coefficients of the surface weight function w _i for various distributions of the flow velocity. Using the obtained coefficients K _p , then the devices are calibrated in a known manner according to [2].

Thus, the proposed solution allows you to verify the electromagnetic flowmeter for any given flow patterns of the measured medium in the channel and thereby extends the functionality of the simulation method of calibration and calibration of electromagnetic flowmeters.

Sources of invention

1. Kremlin P.P. Flow meters and quantity counters. L., Engineering, 1989

2. Patent RU 2146042 C1, 7 G01F 25/00, BI No. 6, 2000.

3. The invention of the USSR N 627343, G01F, BI No. 37, 1978

Claims (1)

A method for checking electromagnetic flowmeters, including placing an induction coil electromagnetic flowmeter in the channel’s working area, integrating the voltage at the output terminals of the coil induced by the magnetic field of the primary transducer, measuring the ratio k _{i of the} integrated voltage of the induction coil to the voltage released on the resistance r included in the power circuit induction coil, and determination of the conversion coefficient of the primary converter of the electromagnetic race odomera, characterized in that in the working area of the channel surface, a plurality (n) of the induction coils operate alternately integrate the output voltage of each coil, the induced magnetic field of the primary device, then calculates the parameters λ _i of the magnetic field intensity at the local surface, on which the corresponding induction coils are placed, and the parameter λ _{i is} calculated by the formula

where C _i is the integration time constant, N _i is the total area of the turns of the i-th coil, and from the obtained values of the parameters λ _{i of} the magnetic field intensity, for all local areas of the channel surface, the conversion coefficient K _{p of the} primary transducer of the electromagnetic flowmeter is calculated by the formula

where W _i is the value of the surface weight function calculated for the i-th local surface of the channel for a given shape of the distribution of flow velocity, D is the diameter of the pipeline.

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