RU2330246C2 - Method for graduating and checking electromagnetic flow meters - Google Patents

Abstract

FIELD: measuring instruments; graduation.

SUBSTANCE: induction coil is placed into the magnetic field of a transmitter in an electromagnetic flow meter. An electrical voltage inducted by the transmitter magnetic field is integrated at the output terminals of the coil. Electric signal values are determined. A voltage is applied to the input of a gauge unit of the electromagnetic flow meter. A variable resistor Rv, being a part of the flow transmitter, sets thereat a unified output signal value, being experimentally determined for every standard size of flow transmitters and proportional to the magnetic induction value. Moreover, the value of said signal is an input signal for a measuring transmitter. Unified graduation factors, being experimentally determined for all the measuring transmitters, are entered into said measuring transmitter using a program. Checking consists in determining the measurement error in respective flow points. In case of a discrepancy between the determined measurement error and the acceptable value, the transmitter or gauge unit is subject to replacement.

EFFECT: extended functional capabilities and simplification of the checking.

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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, their verification by a simulation method.

A known method of calibration and calibration of electromagnetic flowmeters (RU, patent No. 2146042, G01F 25/00, 1999). An induction coil is placed in the magnetic field of the primary converter and the electric voltage is integrated at its output terminals. The ratio of the voltage obtained as a result of integration to the voltage released on the resistance included in the power circuit of the inductor of the primary converter determines the conversion coefficient of the last Kp. The ratio of the signals at the output and input of the flowmeter, when summing the voltage allocated to the resistance included in the inductor power supply to the input of the measuring device, the conversion coefficient of the Kiu measuring device is calculated. The conversion coefficient of the flow meter is defined as the product of the coefficients Kp and Kiu.

This method provides separate verification and interchangeability of primary transducers and measuring devices, however, it excludes the possibility of simultaneously adjusting the results obtained, in addition, for the implementation of this method, a number of calculations are necessary - Kp and Kiu coefficients.

Closest to the proposed method is a method for checking electromagnetic flowmeters (RU, G01F 25/00, 2005), which consists in the following: an induction coil is placed in the magnetic field of the primary transducer of the electromagnetic flowmeter. The magnetic field of the primary converter induces an electric voltage, integrates the electric voltage at the output terminals of the coil. The voltage obtained as a result of integration is compared with the voltage indicated in the nameplate data of the primary converter. If necessary, adjust the voltage to the rated value using a variable resistor. Voltage is input to the input of the measuring device of the electromagnetic converter through a symmetrical resistor voltage divider and voltage values are measured at the points of flow measurement. If necessary, re-adjust the measuring device using variable resistors.

This method provides separate verification and interchangeability of the primary converters and measuring devices, however, the variable resistor is intended only for adjustment during calibration.

The objective of the invention is to expand the functionality of the simulation method of calibration and calibration of flow meters by ensuring the interchangeability of primary converters and electronic units.

This is achieved by the fact that in the proposed method for calibrating and calibrating electromagnetic flowmeters, including placing in the magnetic field of the primary transducer an electromagnetic flowmeter of the induction coil, integrating the electrical voltage at the output terminals of the coil induced by the magnetic field of the primary transducer, and determining the value of the electrical signal, as well as supplying voltage to the input of the measuring device of the electromagnetic flowmeter, a variable resistor Rp, which is part of the first of the flow transducer, set up a unified, experimentally determined for each size of primary flow transducers output signal value proportional to the magnitude of the magnetic induction and being an input signal for the transducer, programmatically calibrate calibration coefficients unified for all transducers, which are experimentally determined, and check consists in determining the measurement error in tvetstvuyuschih flow points, and when not under measurement errors permitted are replaced either primary transducer or measuring device.

At present, primary flow transducers and measuring transducers that make up the kit of an electromagnetic flow meter (or heat meter) are graduated and verified individually. In the event of failure of one of the components of the kit, re-equipment is performed, calibration and verification are repeated with the recording in the electronic unit of (software) individual calibration coefficients inherent only to a specific set of flowmeter (or heat meter). This is largely due to the non-identical technological parameters of the primary flow transducers, such as the inner diameter of the pipeline (lining), the distance between the electrodes, the magnitude of the magnetic induction in the cross section of the pipeline, the distance between the excitation coils (located on the pipeline), the winding data of the field windings, and the parameters of the magnetic system , etc. The problems with ensuring the guaranteed dimensions of the inner diameter of the lining and the distance between the electrodes are largely resolved by purely technological methods. Ensuring the identity of the magnitude of the magnetic induction is a rather complex and expensive problem requiring complicated design and significant material costs.

The proposed method does not require complex design decisions and material costs.

It is known from theory that the useful signal on the electrodes of the primary flow transducer is determined by the formula:

E = B · D · V, where

E is the emf on the electrodes;

B - magnetic induction in the cross section of the pipeline;

V is the flow rate of water.

The magnetomotive force required to excite the magnetic field is determined by the expression:

, где

where

J is the excitation current;

ω is the number of turns of the field winding;

B - magnetic induction in the cross section of the pipeline;

l _in - the distance between the field windings;

M _in - magnetic permeability of air;

K is a coefficient taking into account the magnetic resistance of the core of the magnetic circuit.

From an analysis of the above formulas, we can conclude that by changing the current through the field windings, it is possible to provide such a value of magnetic induction that the useful signal on the electrodes and, as a result, the input signal for the measuring transducer (electronic unit) will be almost the same.

The invention is illustrated in the drawing. The drawing shows a diagram of a device for calibration and calibration of primary converters.

Calibration of instruments in a simulation way consists in determining the value of the control volume (determination of the volume measured by the flowmeter for a certain period of time) and comparing it with the value of the control volume determined during the initial calibration.

The proposed method for calibrating electromagnetic flow meters provides for separate verification of the primary transducer and the measuring device and is carried out as follows.

The drawing shows an electromagnetic primary converter, consisting of two magnetic field excitation coils, an induction coil 2 is installed in the duct channel 1 of the primary converter, which is connected to an integrating converter 3. The excitation coils are supplied from a stable alternating current source 4. When connecting the excitation coils to a source power supply in the channel of the primary converter there is an alternating magnetic field, which induces in the induction coil placed in the channel e primary converter, electrical signal. This signal is integrated using an integrating transducer 3 and fed to the measuring device 5 (voltmeter). The measuring device 5 measures a signal equivalent to the magnitude of the magnetic induction.

In parallel with the field winding, a variable resistor Rp is installed, which is part of the primary flow transducer and allows you to change the pulse current (and, as a consequence, 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 is proportional to the magnitude of the magnetic induction, which is unified for all primary transducers of the same size (conditional pass diameter Du).

On measuring transducers (electronic units), 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, for some reason, the measurement error does not comply, a simple replacement is made either on the primary transducer or on the measuring device and verification (calibration is not performed) of the volume measurement error.

In the proposed method, the variable resistor Rp serves not only to adjust, but also to exhibit a specific value of the output signal, the same for each size of electromagnetic flowmeters.

Thus, the use of the proposed technical solution provides for the assembly of electromagnetic flowmeters with constituent parts — a primary flow transducer and a measuring transducer with programmed calibration coefficients and verification (without calibration of the flowmeter set) for compliance with the measurement error on the flowmeter installation, thereby expanding the functionality and simplifying verification electromagnetic flow meters.

Claims (1)

A method for calibrating and calibrating electromagnetic flowmeters, including placing an induction coil electromagnetic flowmeter in a magnetic field of a primary transducer, integrating an electrical voltage at the output terminals of a coil induced by a magnetic field of a primary transducer, and determining an electric signal value, as well as supplying voltage to an input of an electromagnetic flowmeter measuring device, characterized in that the variable resistor Rp included in the primary transform For flow, a unified, experimentally determined for each size of primary flow transducers type is established, the value of the output signal proportional to the magnitude of the magnetic induction, which is an input signal to the measuring transducer, programmed calibration coefficients unified for all measuring transducers are experimentally determined, and verification is carried out in determining the measurement error at the corresponding points x flow and not under measurement errors permitted are replaced either primary transducer or measuring device.