SU836526A1 - Contact-free electromagnetic rate-of-flow meter - Google Patents

Description

(54) CONTACTLESS ELECTROMAGNETIC FLOWMETER

signals, for example, due to uneven oxidation of the inner and outer surface of the pipeline.

The reliability of the meter is low. The operation depends on the wetting of the pipeline wall with metal, the oxidation of the wetted surface, the state of the magnetic contact sensor CO in the pipeline wall.

The aim of the invention is to improve the accuracy and reliability of measurements.

This goal is achieved in that a contactless electromagnetic flowmeter comprising an excitation current generator, an overhead sensor with an W-shaped core and magnetizing and receiving windings, each of the two receiving windings through an AC signal amplifier and the detector connected to the ratio circuit inputs, the output of which is connected with indicator device; and the excitation current generator is connected to the magnetizing windings and the control inputs of the detectors, two controllable key switching elements, two low-pass filters, a sign analyzer, two linearly controlled time delay elements and a difference integrator are added. The ratio circuit is designed as an inverse conversion circuit; the sensor with the W-shaped core is made with two windings only on the extreme teeth of the core. The detectors are in the form of peak detectors, the outputs of the field current generator associated with peak detectors and the beginnings of the sensor windings.

A common junction of series-connected windings is connected to the device case, the output of the first peak detector is connected through the first low-pass filter and the first variable signal amplifier to the signal inputs of both controlled key switching elements, the outputs of which are connected to the inputs of the difference integrator. The output of the differential integrator is connected to the inputs of the indicator device and the ratio circuit, the output of which is connected to the control inputs of both controlled delay elements. The output of the second peak detector through the second low-pass filter and the second variable signal amplifier is connected to the input of the sign analyzer, the output of which is connected to the input of the second controlled delay element and the control path of the first controlled key switching element through the first controlled decay element, the output of the second controllable delay element is connected to the control input of the second control key switching element;

FIG. 1 shows a block diagram of the device; in fig. 2 - diagrams / in FIG. 2, and shows the form of the generator signal, the y axis represents the current value in time plotted along the X axis on an arbitrary scale; in fig. 2.6 shows the signal view on one of the sensor windings, on the other it is similar and shifted by the time of transport delay t. This is an amplitude modulated signal, the voltage amplitude is plotted along the y axis, and the time is along the X axis; in fig. 2, an amplified signal highlighted by a peak detector, a filter and a variable component amplifier is shown, the current voltage is plotted along the Y axis, the time scale is the same for the X axis and the time scale is the same as for diagram 26 / in FIG. 2, r - the same signal allocated by another channel. This signal has the form of a signal of diagram 2, c, and is shifted by t the transport time for the flow of the magnetic sounding zones of the sensor; in fig. 2, d shows the type of signal at the output of the analyzer sign. The signal of a logical impulse corresponds to one sign of the signal, and the pause to another. The voltage axis of the logical signal is plotted along the y axis, time is plotted along the X axis (on the scale of Fig. 2, bd); in fig. 2, e shows the relationship between the transport lag time tg and the delay time t of the first element and t of the second delay element. The line of drift (dotted line) shows the location of the equal-phase signals for the area of the area in the center of the delay time interval of the second delay element, which is set automatically in the operation of the device; in fig. 2, the dependence of the output voltage value on the flow velocity is shown; the flow velocity is plotted along the x axis, and the output voltage is plotted along the y axis.

The elements of the device are interconnected as follows.

The two winding sections of the sensor 1 are connected in series and connected to the output of the excitation current generator 2 to which the inputs of peak detectors 3 and 4 are connected at the same points. The outputs of the detectors are connected via two multi-link low-pass filters 5 and 6 to the inputs of the AC signal amplifiers 7 and 8, and the output of amplifier 7 is connected to the signal inputs of two controlled key switching elements 9 and 10, the outputs of which, in turn, are connected to the inputs of the ratio circuit 11. The output of the variable signal amplifier 8 is connected via analysis the torus of the sign 12 to the input of the first controllable delay element 13, the output of which is connected with the input of the second delay element 14 and with the control input of the first control key switching element 9, and the output of the second controllable delay element 14 is connected with the control input of the second controlled key switching element 10. The output of the differential integrator 11 is connected to the indicator device 15 and through the inverse conversion circuit 16 to the control inputs of both delay elements 13 and 14. The average point of the sections is The sensor current is connected to the body of the amplifiers of the measuring device.

Consider the operation of the device in the dynamics. Turbulence and inhomogeneities carried by the liquid metal medium circulating inside the pipeline alternately intersect two probing magnetic fluxes created by two windings of sensor 1 placed on the extreme teeth of the U-shaped magnetic circuit fed from the source of the excitation current 2. The alternating current generator with very large internal resistance. The output of the generator is isolated. A variable voltage is generated on the inductive resistances of the x / windings. Transported liquid metal flows, inhomogeneities and turbulence, create fluctuations in the amplitude of the alternating voltage on the sensor windings separated by the transport time of inhomogeneities transferred by the flow of liquid metal between the two zones of magnetic sounding. The frequency and amplitude of the excitation generator current are chosen sufficient for deep penetration through the pipe wall into the stream of liquid metal (for example, 30 Hz - 1 kHz, 0, 1 a).

Peak detectors 3 and 4 cut off the signal of a constant amplitude, and multi-link low-pass filters smooth out carrier pulsations, the constant component is not perceived by variable signal amplifiers 7 and 8, which amplify the fluctuation of the passage of non-dododes carried by the flow of liquid metal. The relative temporal displacement of the selected fluctuations is inversely proportional to the speed of the controlled flow. The delay signal is fed to the signal inputs of the key switching elements 9 and 10, and the primary signal to the analyzer, the sign 12, the logical output of which passes the steps of both elements of the linearly controlled delay elements 13 and 14 and is fed to the control of the key switching elements 9 and 10 The outputs of the key switching elements 9 and 10 are connected to the inputs of the summation and subtraction of the ratio circuit 11. Depending on the magnitude of the phase shift of the delayed signal and.

the signal passed through the various delay stages 13 and 14 at the output of the circuit, the voltage ratio changes so that this signal, passing through the inverse value circuit 16, controls both delay circuits, approximating, differently the delayed signal with one and both delay circuits to (positive and negative) phase shift relative to the delayed signal. This sets the compensation

i

where t is the relative offset time of the signals;

t is the delay time of the first element;

t - time ssshderzhki the second element.

The delay time of the second element for a better time resolution is chosen less than the delay time of the first delay element, which is achieved by choosing different control conversion factors. At the same time, the voltage is set at the output of the differential integrator

V. - ".

t l 2

where.i ,,,, „- output voltage inPbiX

Tegrator;

K - correspondence coefficient, S - distance between zones

5 magnetic sounding; . t, -time delay first

an item; tx2 - delay time of the second

delay element; 0 V - speed.

This voltage is applied to the indicator with the Scale of Reference of the flow rate of the liquid metal during non-stationary use of the proposed device, or directly at the flow rate for stationary use on the pipeline, of a certain diameter.

50

Claims (2)

Invention Formula  A non-contact electromagnetic flowmeter comprising an excitation current generator, an overhead sensor with 55 W-shaped core and magnetizing and receiving windings, each of the two receiving windings through an AC signal amplifier and detector. Connected to the circuit inputs 60 ratios, the output of which is central to the indicator device, and the exciter current generator is connected to the magnetizing windings and control inputs of the detectors, about 65 and 65 so that, in order to improve accuracy and reliability, two controllable key elements are added to the flow meter circuit switching elements, two low-pass filters, a sign analyzer, two linearly controlled time delay elements, and a difference integrator; the ratio circuit is ELECTED in the form of an inverse-value conversion circuit; the sensor with the W-core of the core is made with two windings only on the extreme teeth of the core, the detectors are made in the form of peak detectors, the outputs of the excitation current generator are connected with the peak detectors and the beginning of the sensor windings, the common point of the series-connected windings is connected to the device body, the output of the first peak detector through the first low-pass filter and the first variable signal amplifier is connected to the signal inputs of both controlled key switching elements, the outputs of which are connected with the inputs of the differential integrator, the output of the differential integrator is connected to the inputs of the indicator device and the ratio circuit whose output is connected to the control inputs of both controllable delay elements / output of the second peak detector via a second low-pass filter and the second variable signal amplifier the input of the sign analyzer, the output of which through the first controllable delay element is connected to the input of the second controllable delay element and the control input of the first controllable key switch the control element, and the output of the second controllable delay element is connected to the control input of the second control key switching element. Sources of information taken into account in the examination 1. N. Tsirkunov. ZheygurB.D., Simone G.Ya. and Kalnin R.K. Contactless control of the flow of liquid metals, Riga, Knowledge, 1973, p. 22 2. Tsirkunov V.E., Zheigur B.D., Simone G.Ya. and Kilnin R.K. Contactless control of the flow of liquid metals. Riga, Knowledge, 1973, p. 236 (prototype). 1g. / / D / A "/ A" ll / IJPP P P PPG e / xA / Vv Xr, well "Y-