SU557271A1 - Method of measuring flow (velocity) of electrically conductive media - Google Patents

Description

one

The invention relates to the field of contactless measurement of the flow rate (velocity) of electrically conductive media using inductive-ion flowmeters.

A known method of contactless measurement of the velocity of electrically conductive media by creating a pulsating field of excitation measures the amplitudes of the electromagnet field at the points corresponding to the nodes and antinodes of the field of excitation and the controlled speed is judged by the ratio of these amplitudes. However, the measurement results depend on the magnitude of the magnetic field in the gap, which varies with the mutual shifts of the inductors. Since it is almost impossible to ensure the absolute identity of both groups of cutters that measure the amplitudes of the magnetic field at the points of the nodes and the field properties of the excitation field, this method of measuring the flow requires calibration of at least one point of its metrological characteristics.

There is a known method for measuring the flow rate, according to which, using inductors with short pole divisions, in space simultaneously create two opposite-betting magnetic fields with multiple speeds of motion. The difference in the magnitudes of the secondary magnetic fields of the currents from both primary magnetic fields in a stationary medium placed in the gap by the inductors is proportional to the difference in the speeds of movement of these fields. When moving conductive

The difference between the magnitudes of the secondary fields of the currents of both primary fields is proportional to the difference between the relative velocities of these fields and the medium. From the measured difference in the values of the secondary fields, the velocity of the medium is judged. The known method does not require pouring calibration, however, firstly, the dependence of the magnitude of the secondary fields of currents created by the primary magnetic fields excited by windings with multiple pole divisions in the medium is the same for small values of the relative gap (where d - the gap between the inductors; t pole division of the winding) and dimensionless

frequencies fjJ yUodwb (where yUgO b is, respectively, magnetic permeability, conductivity, and medium half-thickness;

SLR - circular frequency current supply), for example, for such an electrically conductive medium as mercury at small thicknesses of the pipeline. For a wide range of these parameters, which are often found in practice, for example for alkali metals, the above dependences are different for fields with different wavelengths. This brings additional errors into the dimension. Secondly, in the case of measuring the flow rate of high-temperature media in the indicating roll of a flow meter that implements a known method, in addition to the signal from the secondary fields of currents induced in the medium by the primary magnetic fields, the parasitic emf is also induced. This is due to the fact that a change in the linear dimensions of the inductors when they are heated B, of varying degrees, affects the windings with different pole divisions and, therefore, the fields excited by them. As a result, additional measurement error is observed.

The purpose of the invention is to improve the accuracy of measuring the speed of movement of electrically conductive media. This is achieved by measuring the flow rate of electrically conductive media using oppositely moving magnetic fields with multiple speeds, first alternately creating each of the running magnetic fields and determining the signals from currents induced in the medium by each of the fields when stationary and two-dimensional the speed of the medium, then they create both counter-running fields, adjust the calibration point of the characteristic according to the ratio of the difference of the signals with the fixed and moving medium of each of the fields. When measuring the flow rates of electrically conductive media at high temperature, the signal from the currents induced in a stationary medium simultaneously by both counter-traveling fields is corrected accordingly to signals in the stationary medium from each of the fields.

In the method described, the magnitudes of the secondary magnetic fields of the currents in a stationary medium induced by each field are measured. These values are proportional to the speeds of field movement. The medium is then set in motion and an arbitrary speed is set. At the same time, the signals from currents arising in the moving medium are measured for each 1X1 of the fields. For each of the fields, the difference of the signals from the current is determined with the motionless and moving, with the medium. The ratio of these differences determines the difference in the dependences on the velocity of the medium on the magnitudes of the secondary magnetic fields of the currents induced in the medium by each of the primary fields.

The method takes into account the non-identity dependencies on the velocity of the medium; the magnitude of the signals from the currents in the medium.

each of the magnetic fields. The velocity of the medium is determined by the formula

V Vo (2 / i-H Jf), VQ is the speed of the medium at which the magnitudes of the secondary magnetic fields from both primary

the counter-running fields are equal to 0 in the case of the identity of their dependence on the velocity of the medium.

If the above dependences are identical, i.e. at 1, we get V.

When measuring the flow rate of high-temperature media to eliminate the influence on the measurement results of parasitic emf, the signals from the currents induced in the medium by each of the fields with a fixed

the environment, the proportionality of each of these motion signals of the corresponding field is checked. If the proportionality is violated, then when creating a superposition of both fields, the signal from currents induced in a stationary medium by both oppositely running fields simultaneously is corrected accordingly to signals in a stationary medium from each of the running fields. The method can be implemented in a flow meter (Fig. 1) containing an inductor 4 with two groups of 2 and 3 windings with multiple pole divisions. Electroconductive medium 4 is placed between the inductors 1. The flow meter includes a power source 5 to which are connected through the three-position switch 6: in position I of switch 6 - group 2 of windings, in position II - group 3 of windings, and in position 111 - both groups 2 and

3 connected in series. In addition, the flow meter contains receiving coils 7 connected through an amplifier 8 to a phase detector 9. The reference voltage to the phase detector 9 is supplied through the phase shifter 10 from the power source 5. The output of the detector 9 is connected to the indicator 11, through the sensitivity regulator 12. The detector 9 detects the signal in accordance with the phase supplied to it from the phase shifter 10, which regulates the phase of the voltage supplied to it from source 5.

In the case of measuring the flow rate of high-temperature 60% conductive electrically conducting media, the output

The detector E is connected to the sensitivity controller 12 through the compensation unit 13, which can be used as a differential amplifier connected to the compensation source 14. The latter is a source of stabilized constant voltage (Fig. 2). The compensation unit 13 subtracts the signals fed to it from the detector 9 and the source 14.

On this flow meter, the method is implemented as follows.

In the absence of the controlled medium 4 in the gap of the inductors 1, the switch 6 is set to position III, wherein both groups 2 and 3 of the windings are connected in series and connected to the power source 5 and zero is set on the indicator 11. Then, in the gap of the inductors 1, a fixed controlled medium 4 is placed. Setting switch 6 alternately to position I, in which only group 2 of windings of inductors 1 is connected to the power source, and then to position II, in which only group 3 of windings is connected to the power source The fact that the induced emf in the receiving coils is proportional to the corresponding field speeds created by the winding groups connected in this case. When setting switch 6 to position P1 emf induced in the receiving coils, equal respectively to the difference in emf at the positions of the switch I and II. After recording the output device with the stationary medium at the positions I and 11 of the switch 6, the medium is set in motion and at an arbitrary speed of movement of the medium again the indicator 11 is fixed at the positions of the I and P switch 6. Then The difference between the readings of the indicator 11 when the medium is stationary and when it moves for the position of the switches I and II. And they find the ratio of these quantities, which determines the difference in the dependences of the values of the secondary magnetic fields of the currents induced by each of the primary fields in the medium, as the medium moves. Then, the corrected calibration characteristic point corresponding to the zero output 4y signal V - VQ (2 /: if 5) is calculated. If the above dependences are identical: i and V Oud - Then, using the sensitivity adjuster 12 in position III of the switch 6, the indicator is corrected eleven,

In the case of measuring the flow rates of high-temperature media to eliminate the influence on the measurement results of the parasitic emf. J at a fixed environment fix

the indicator 11 when alternately turning on the positions I and II of the switch 6. If it is found that the signals received in this case are not proportional to the pole divisions of the connected windings, then when setting the switch 6 in half-clock III, the indicator 11 is corrected by supplying a compensating signal from source 14 to the input of the compensation block 13.

Claims (1)

Invention Formula A method for measuring the flow rate (velocity) of electrically conductive media, based on the use of two variable magnetic fields running in opposite directions, characterized in that, in order to improve the measurement accuracy, the ratio of the penetration difference of each of the fields in a stationary and moving medium is determined and this ratio is in the form of an amendment to the measurement result.