RU2384823C1 - Calibration method of electromagnetic flow metres, and flow simulator for implementation thereof - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: in measuring channel of primary flow converter 2 there installed is simulator 1 in the form of cylindrical container made from non-magnetic and non-conductive material and filled with measured medium and equipped with sealed electrodes located diametrally opposite in one line with electrodes E1 and E2 of primary converter 2. Throughout the length of simulator 1, in electrodes installation place there made are slots in which porous current-conducting material is laid. Primary converter 2 is powered with constant current from the measuring device of electromagnetic flow metre. To the measuring device there introduced are calibration coefficients which are constant for all measuring devices with primary converters of one and the same standard size. In order to simulate the liquid flow rate, back-and-forth movement is transmitted to simulator 1, during which the simulator electrodes contact primary converter 2 electrodes. Signal proportional to flow is picked up from electrodes E1 and E2, and obtained signal is fed to the measuring device input, converted and represented in the form of measured liquid volume.

EFFECT: invention provides separate calibration of primary converter and measuring device of electromagnetic flow metres in conditions close to actual environment as much as possible at simultaneous simplification of calibration.

2 cl, 2 dwg

Description

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

A known method of calibration and calibration of electromagnetic flowmeters (USSR Author's Certificate No. 165910, G01F, 1964), which provides for the conversion of the magnetic field of the primary transducer into an electrical signal, is equivalent in its parameters to the signal excited between the electrodes when a given flow rate of conductive fluid flows through the channel. This method includes measuring the parameters of the channel of the primary Converter; the conversion of the magnetic field of the primary Converter into electrical voltage using an induction coil placed in the channel; integrating the electrical voltage obtained at the output terminals of the induction coil using an electronic converter, dividing in a certain ratio using a resistive divider, and summing the received signal, which as a result of these transformations becomes equivalent to the signal excited between the electrodes during a given fluid flow, to an electromagnetic measuring device flow meter.

The disadvantage of this method is the inability to separately verify the primary transducer and the measuring device of the electromagnetic flow meter.

A device for calibrating and calibrating electromagnetic speed converters is known, comprising a magnetic field transducer in the form of an induction coil, the turns of which are located at the levels of the surface weight function (USSR Author's Certificate No. 1467399 A1, 03/23/1989).

With respect to liquid velocity transducers, the magnetic field transducer should substantially repeat the entire working surface of the velocity transducer in contact with the medium to be measured, which usually has a complex cylinder shape with an end surface.

A disadvantage of the known device is the low-tech manufacturing and the difficulty of placing coil turns in accordance with the difficult working surface of the speed Converter; there is no possibility of producing such a complex configuration of the surface of the induction coil by an automated and printing method, therefore, there is no possibility of multiple replication of it with high accuracy and low cost.

A known method of calibration of electromagnetic flowmeters (patent RU No. 23232651, G01F 25/00, 2005), comprising converting the magnetic field of the primary transducer into electrical voltage using an induction coil placed in the flowmeter channel, integrating the electrical voltage obtained at the output terminals of the induction coil , division in a certain ratio using a divider and summing the received signal to the measuring device of the electromagnetic flowmeter, free space in the working volume of the channel An electromagnetic flow meter designed to measure flow is filled with a measured medium placed in sections of a container made of non-magnetic and non-conductive material.

In the known device according to patent No. 23232651, the free space in the working volume of the channel of an electromagnetic flowmeter designed to measure the flow rate of a measured medium is filled with a measured medium placed in sections of a container made of non-magnetic and non-conductive material. If the induction coil is a flat printed circuit board placed in the channel in the plane of the axis of the channel and the line connecting the electrodes, then a corresponding narrow slot is provided in the container into which the induction coil is inserted. If the induction coil is made in the form of a cylindrical surface and is installed in the channel along the channel surface, the outer diameter of the container is made smaller than the inner diameter of the induction coil. During calibration and verification, the container is inserted into the flowmeter channel along with the induction coil.

The disadvantages of the known method and device are the inability to separately calibrate the primary transducer and the measuring device of the electromagnetic flow meter, as well as the fact that the important element of the construction of the primary transducer, electrodes, is not involved in the calibration and calibration method. The device for calibration and verification also includes such additional devices as a device for integrating and converting signals from an inductor, resistive dividers, which complicates and increases the cost of the calibration and verification process.

Closest to the proposed method is a method for calibrating and calibrating electromagnetic flowmeters (patent RU, No. 2330246, G01F 25/00, 2008), in which, when calibrating primary flow transducers, a variable resistor Rp sets a standard for all primary transducers of the same size (conditional diameter pass DN) value of the output signal proportional to the magnitude of the magnetic induction.

On the measuring devices (electronic blocks), calibration coefficients that are the same for all measuring transducers are determined by software, which are determined experimentally for each size of the primary flow transducer (corresponding to the nominal diameter of the DN).

The verification method of electromagnetic flowmeters consists in completing the flowmeter with a primary flow transducer and an electronic unit, performing verification in any known manner and determining the error at the corresponding flow points. If the measurement error does not correspond for any reason, a simple replacement is made either on the primary transducer or on the measuring device and verification (calibration is not performed) of the measurement error.

This method allows separate verification of the primary transducer and the measuring device of the electromagnetic flow meter, but this method of calibration and verification does not involve an important element of the construction of the primary transducer - electrodes. The device for calibration and verification, as in the previous device, includes such additional devices as a device for integrating and converting signals from the inductor, resistive dividers, which complicates and increases the cost of the calibration and verification process.

These disadvantages are eliminated in the present invention.

The objective of the invention is to expand the functionality of a simulation method of verification by providing separate verification of primary transducers and measuring devices of electromagnetic flowmeters, approximation of calibration and verification conditions to the actual operating conditions of flowmeters, reducing the number of instruments and measuring instruments during calibration.

This is achieved by the fact that in the method of calibration of electromagnetic flowmeters, which consists in the fact that a variable resistor Rp, which is part of the primary flow transducer, sets a unified experimental value for each size of the primary flow transducers of the output signal, proportional to the magnitude of the magnetic induction, and the output signal is an input signal to the measuring device, is introduced programmatically into the measuring device unified for all measuring transducers, calibration coefficients determined experimentally, place a flow simulator in the measuring channel of the primary transducer, convert the received signal of the primary transducer to electrical voltage and supply the received signal to the measuring device of the electromagnetic flow meter, flow simulator filled with the measured liquid and equipped with electrodes, report reciprocating motion while the electrodes of the simulator are in contact with the electrodes of the primary a flow transducer, from which a signal proportional to the flow rate is taken, the received signal is fed to the input of the measuring device, converted and displayed as a measured volume of liquid.

A flow simulator, which is a cylindrical hollow container filled with a measured liquid, with thin walls made of non-magnetic and non-conductive material, along the entire length of the cylindrical surface of which grooves are made in the place of installation of the electrodes of the primary flow transducer, filled with a porous conductive composition designed to provide diametrical contact between the grooves - opposite of the sealed electrodes of the simulator with the electrodes of the primary converter gathering, while the outer diameter of the simulator with the necessary accuracy corresponds to the inner diameter of the measuring channel of the primary Converter.

Using the proposed method and device, the real conditions of calibration, operation of flowmeters are simulated, the real principle of operation of electromagnetic flowmeters (the law of electromagnetic induction) is implemented.

The invention is illustrated by drawings.

Figure 1 shows the device with which the proposed method for calibration and calibration of electromagnetic flowmeters is carried out. Figure 2 - flow simulator. The simulator is a cylindrical container 1 made of non-magnetic and non-conductive material, filled with a measured medium. The outer diameter of the simulator 1 is made with a certain accuracy and is equal to the inner diameter of the channel of the primary flow transducer 2. The simulator 1 has sealed diametrically opposite electrodes 3 (one is conventionally shown in FIG. 2) located in line with the electrodes E1 and E2 of the primary flow transducer 2. The entire length of the simulator 1 in the installation area of the electrodes 3 has grooves 4 in which a porous conductive material is laid.

The method is as follows.

The simulator 1 is installed in the measuring channel of the primary flow transducer 2 so that the electrodes 3 of the simulator 1 and the electrodes E1 and E2 of the primary flow transducer 2 are in electrical contact.

To simulate the flow rate of the fluid (simulating flow) using a special device (not shown in the drawing), the simulator 1 is given a reciprocating movement in the cavity of the measuring channel of the primary flow transducer 2.

Parallel to the field winding, a variable resistor Rп is installed (Fig. 1), which is part of the primary flow transducer and allows you to change the pulse current (and, consequently, the magnitude of the magnetic induction) flowing through the field windings without changing the total current from the current source.

When calibrating the primary flow transducers with a variable resistor Rп, a value of the output signal proportional to the magnitude of the magnetic induction is set that is unified for all primary transducers of the same size (nominal pass diameter Du).

On the measuring devices (electronic blocks), calibration coefficients that are the same for all measuring transducers are determined by software, which are determined experimentally for each size of the primary flow transducer (corresponding to the nominal diameter of the DN).

The magnitude of the magnetic induction of the magnetic field of the primary transducer 2 is set by the method described above, and is the same for all primary flow transducers of the same size.

The primary flow transducer 2 is powered by a bipolar stabilized current from a measuring device of an electromagnetic flow meter. Calibration coefficients are introduced into the measuring device, which are determined experimentally and are constant for all measuring devices with primary transducers of the same size.

When the simulator 1 moves inside the measuring channel of the primary transducer 2 in the magnetic field of the inductor, the emf is induced on the electrodes 3 of the simulator 1:

e = -B · D · V

where is the magnetic induction;

D is the distance between the electrodes;

V is the speed of movement of the simulator.

By changing the speed of the simulator (simulating a change in fluid flow in the flowmeter installation), we change the value of the input signal proportional to the flow rate supplied to the measuring device.

Using a simulator, the real nature of the signal from the electrodes is achieved. The signal from the electrodes is fed directly to the measuring device without intermediate devices (integrators, dividers), the primary converters and measuring devices are interchangeable.

Claims (2)

1. The method of calibration of electromagnetic flowmeters, which consists in the fact that a variable resistor Rp, which is part of the primary flow transducer, sets a unified experimental value for each size of primary flow transducers of the output signal proportional to the magnitude of the magnetic induction, and the output signal is an input signal for measuring device, programmatically injected into the measuring device unified for all measuring transformations experimentally determined calibration coefficients are placed in the measuring channel of the primary transducer a flow simulator, converting the received signal of the primary transducer to electrical voltage and feeding the received signal to the measuring device of the electromagnetic flow meter, characterized in that the flow simulator filled with the measured liquid and provided with electrodes is returned - translational motion, while the electrodes of the simulator are in contact with the electrodes of the primary a flow generator, from which a signal is proportional to the flow, the received signal is fed to the input of the measuring device, converted and displayed in the form of a measured liquid volume. 2. A flow simulator, which is a cylindrical hollow container filled with a measured liquid with thin walls made of non-magnetic and non-conductive material, along the entire length of the cylindrical surface of which grooves are made in the place where the electrodes of the primary flow transducer are installed, filled with a porous conductive composition designed to provide electrical contact located in grooves of diametrically oppositely sealed electrodes of the simulator with electrodes of the primary transducer Flow rate, the outer diameter of the simulator corresponds to the required accuracy of the measuring channel to the inner diameter of the primary device.

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