JPS5934963B2 - Method and device for measuring liquid over time using a pressure measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to liquid measurement, and in particular to a method for measuring liquid over time using a pressure measurement device, and an apparatus for carrying out the method when measuring high temperature corrosive molten metals. Regarding.

The invention can be most advantageously used in metallurgical and foundry processes for the automation of metered pouring of liquid metal into molds.

A wide range of applications have been found with pressure liquid measuring devices,
in that case, the delivery of the metered portion rises in the discharge conduit under the pressure of the liquid being metered;
and subsequent discharge of liquid into a container through an opening provided above the highest level of liquid in the conduit.

Such measurement devices are most useful for measuring hot, aggressive, molten metals, especially liquid metals. Aerodynamic and electromagnetic liquid metal measurement devices are most commonly used.
Methods of measuring liquid metal by weight, by volume and by time (over time) by using pressure measuring devices are known in the prior art.

Temporal measurements have found the widest application, as they are the simplest measurements in some cases, e.g.
．． 1 to 1.0K2) is the only possible method. The movement of the liquid during the course of time-lapse measurements consists of several stages: (1) filling of the discharge conduit up to the discharge opening; (2) controlled discharge (outflow of the liquid under applied pressure); (3) inertial discharge (discharge of liquid after removal of pressure); and (4) return to the initial level of liquid in the discharge conduit. The movement of liquids is characterized by instability, which arises primarily from fluctuations in the applied pressure.

However, even if the pressure is constant over the measurement cycle,
The liquid velocity and rate of liquid ejection from the metering device varies over a significant portion of the cycle due to the substantial influence of inertial forces. In imprinting a small metered portion of liquid, its speed and flow rate vary over the entire metering cycle. Variations in the pressure applied to the liquid are one of the factors that influence the size of the measurement part; other factors include liquid level in the container, hydraulic resistance of the discharge conduit and variations in the physical properties of the liquid. do.

Fluctuations in liquid level generally have the strongest effect.

If the average value of the applied pressure and the time of its action are constant, the mass of the measuring part decreases as the liquid level in the container decreases, ie this occurs because of the following reasons. a) increasing the filling time of the discharge conduit; b) decreasing the liquid velocity at the beginning of the discharge; c) decreasing the overpressure during the course of controlled discharge; d) decreasing the liquid velocity at the beginning of this measurement phase and , a decrease in the mass of the liquid flowing out during the inertial discharge produced by the increase in the pressure difference acting on the liquid during this period and determined by the liquid level in the container.

A measuring method has been proposed in which the liquid level is first maintained constant using one pressurizing means, and then a constant additional pressure is generated by another means during the measuring time (USSR Inventor's Certificate No. 129, (See No. 307).

The above-described metering method and device requires a complex configuration of the metering device due to the considerable extra pressure and pressurization means required to maintain a constant level of liquid in the discharge conduit. Measurement of active molten metals at high temperatures, especially liquid metals, involves the difficulty of maintaining the same level of molten metal, i.e. the discharge conduit is blocked at the metal-air interface by crystallized metal or slag. Ru.

Furthermore, heat losses of the molten metal in the discharge conduit must be compensated for. The pressure on the liquid being metered is increased by the air metering device before the start of the discharge of the metering part, and then a certain amount of compressed air is introduced into the gas-tight container of the metering device.

In this method, the measurement accuracy is affected by the uncertainty in the actual characteristics of the pressure increase before the start of the discharge, and by the decrease in the actual excess pressure as the free space of the vessel increases during the process of discharging the liquid. The reduction in the amount of molten metal released during the third stage of measurement (during inertial release) has the opposite effect. Since the above-mentioned methods do not give the desired measurement accuracy, simpler methods giving the same results have found the most widespread application in the measurement of active molten metals at high temperatures. According to one method of eliminating the influence of the increasing filling time of the discharge conduit on the mass of the measuring part (see Ciekoslovakia Patent No. 115,834), the measuring time is measured not from the beginning of pressurization. The front of the liquid stream is counted from the time it passes through a monitored cross-section of the discharge conduit, which cross-section is generally chosen close to the discharge opening and is provided with an appropriate monitoring device.

This method of measuring liquid over time using a pressure measuring device is a process of lifting the liquid in the discharge conduit by raising the pressure from the initial level of the signal at the start of measurement, until the front of the liquid stream is discharged. detecting when a monitored cross-section of the conduit is passed, ejecting liquid under a pressure varied by the program from which execution of a predetermined program begins, and thereafter reducing the pressure; . However, in order to improve measurement accuracy,
The remaining factors must also be removed, but this cannot be done with the methods described above.

In order to stabilize the measured quantity, according to one refinement of the method, the measuring time is corrected as the liquid level decreases;
The level can be measured directly or determined indirectly, for example as a function of the sequence number of the measured quantity. The method was adapted to measure aluminum alloys. AGAL6OO air measuring device (Otsutoji Anchor Company, FRG)
This will be realized in The relationship between constant mass level fluctuations of the measured quantity and measurement time is non-linear, and such corrections require complex electronic equipment.

Furthermore, for active molten metals (metals, slags, fluxes) at high temperatures, continuous measurement of the liquid level in the vessel is difficult to achieve, and the achieved accuracy of such measurements is low. . On the other hand, indirect measurement methods take into account the changes in the volume of the measuring device's container during the course of operation and the cumulative measurement error of the deviation of the initial liquid level in the container (after filling) from its rated value. Since there is no difference, the accuracy given by the method is similarly low. Other examples of correction have also been proposed that vary the measurement time depending on the time the liquid passes through the measurement length of the conduit. However, upon investigation, it was discovered that this relationship is quite complex and requires special electronic equipment. Moreover, in this case the measurement accuracy is influenced considerably by changes in the conduit cross-sectional area and by other variable factors. The use of the above method for measuring high temperature active molten metals is most conveniently achieved using a channel type induction furnace equipped with a control system.

(“Ulnchshen” by M.R. Twin etc.
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atne, 1975, pp. 113-114). The device has a channel system communicating with each other and with the liquid container and further with the discharge conduit filled with the liquid to be measured.

The current in the liquid is generated by an inductor whose closed magnetic core surrounds one of the channels and whose windings are supplied with an alternating current. The number of inductors is chosen according to special conditions. The connection point of at least one channel with the discharge conduit is surrounded by an electromagnet adapted to generate a magnetic field in the liquid that interacts with the electric current in the liquid. The electromagnet typically generates an oscillating LC with a capacitor connected in parallel.
It has one main winding forming a circuit, which winding is supplied with current via a voltage converter which varies the electromagnetic supply voltage according to the pressure variation pattern set by the control system. The control system has a unit for setting the program for controlling the electromagnetic supply voltage and a unit for controlling the voltage converter.

The electromagnet also has compensation windings, the number of which is equal to the number of inductors and connected in series with the inductor windings.

Apart from the above-mentioned elements, the device has a liquid detector located in the monitoring section of the discharge conduit and operatively coupled to the programming unit.

Advantages of the metrology device described above include low pressure control lag, effective compensation for heat losses in the molten metal, high power factor of the electromagnet and low power resulting from the voltage converter.

However, such measuring devices are characterized by a non-linear dependence of the generated pressure on the electromagnetic supply voltage, which non-linearity is characterized by a progressively decreasing amplitude of the first harmonic of the voltage; A particularly large control angle results from a change in the phase shift angle between the harmonics and the current in the molten metal at low pressures. Due to the linear dependence of the generated pressure on the electromagnetic supply voltage of the measuring device over the entire pressure variation range, the present invention provides a constant pattern of It is an object of the present invention to provide such a method and device for measuring liquid over time using a pressure measuring device which ensures higher measurement accuracy by maintaining liquid velocity changes.

In the present invention, as a specific invention, there is provided a method for measuring liquid over time using a pressure measuring device, which method increases the pressure of liquid in a discharge conduit by increasing the pressure from an initial level in response to a measurement start signal. under the action of a pressure varied by a predetermined program which moves upward and detects the point in time when the front of the liquid stream passes through one monitored cross-section of the discharge conduit, and from the moment of said passage the execution of the program is started. In a method for measuring liquid over time using a pressure measuring device, the increase in pressure is caused by the front of the liquid flow passing through the cross section to be monitored. By changing the pressure at a constant rate such that the velocity of the liquid flow is constant and by a predetermined program, the pressure reached at the point when the front of the liquid flow passes through the monitored cross-section and the reduction in pressure is done at a constant rate until the liquid in the conduit drops below the cross section being monitored, the rate of change in each pressure remaining constant throughout the measurement cycle. Provided is a method for measuring liquid over time using a pressure measuring device characterized by:

The method of the invention ensures the constancy of the measuring section with changing liquid levels in the container.

The pattern of liquid flow rate changes during the measurement process and the overall liquid discharge time are the same for all measurement cycles. Maintaining the rate of pressure increase during a first time interval whose length is determined by the required liquid flow rate, followed by maintaining the pressure constant during a second time interval whose length is determined by the metered volume. Therefore, it is reasonable to vary the pressure according to a predetermined program.

Such improvements in the method allow pressure change programs to be implemented using relatively simple control systems.

In some cases it may be expedient to start from the time when the liquid is lowered below the monitored cross-section of the discharge conduit and the pressure reached at this time is reduced by a predetermined amount.

This ensures that the initial liquid level in the discharge conduit remains constant with respect to the discharge opening in every measurement cycle without directly determining said level, so that contamination of easily oxidized alloys is reduced and the overall measurement Time constancy is achieved.

It is useful to maintain the rate of pressure drop for a predetermined period of time, beginning when the liquid drops below the monitored cross section of the discharge conduit.

When a conductive liquid is measured using an electromagnetic pump having two electromagnetic systems (where one of the two electromagnetic systems operates to generate an electric current in the liquid) under voltage fluctuation conditions of the power supply. (and the other operates to generate a magnetic field in the liquid that interacts with the current in the liquid), keeping the rate of pressure change the same during all measurement cycles is
An electromagnetic system operating to generate a magnetic field in a liquid has a magnitude equal to or less than 2 of the stabilized power supply voltage relative to its actual value.
This is effectively done by supplying a voltage equal to the multiplier value.

Thereby, the installed power capacity of the mains voltage stabilizer is considerably reduced, the accuracy of the measurement is increased, and the stabilized power is reduced by several times relative to the overall power consumed by the measurement device.

In the above case, the electromagnetic voltage control system operates to generate a magnetic field in the liquid, the magnitude of which is equal to the difference between the stabilized double value of the main voltage and its actual value. By supplying a voltage, it can be simplified by keeping the rate of change of pressure the same in all measurement cycles.

The above object is also achieved by an apparatus for carrying out the method when an electrically conductive liquid is to be metered, and according to the invention the apparatus comprises a discharge conduit filled with the liquid being metered, each other and also a system consisting of a channel conduit in communication with a container and a discharge conduit, having at least one inductor operative to produce an electric current in the liquid, the closed magnetic core of the inductor surrounding one of the conduits; The winding is supplied with an alternating current and the connection points of at least two channel conduits with the discharge conduit are connected to a pressure set by a control system having a unit for setting the electromagnetic supply voltage and a program for controlling the voltage converter control unit. having at least one main winding with a capacitor connected in parallel that is supplied with current through an electromagnetic supply voltage converter according to a changing pattern to create a magnetic field in the liquid that interacts with the current in the liquid. It is surrounded by electromagnets operated to generate electricity and further has compensation windings connected in series with the inductor windings, the number of which is equal to the number of inductors, and also a liquid detection device provided in the monitored cross section of the discharge conduit. and the voltage converter is a voltage pulse shaper of an LC circuit composed of an electromagnet and a capacitor, the amplitude of the pulse is controlled according to the pressure fluctuation program, the frequency of the pulse is equal to the frequency of the induced current, The capacitance is selected such that the free oscillation frequency within the LC circuit is within 1 to 1.5 of the frequency of the pulses at the pulse shaper output. This configuration of the device allows for a harmonic configuration of the output voltage over the entire control area giving a linear relationship between voltage and pressure for higher pressures at lower voltages and for lower power consumption. given constancy.

The pulse shaper in the device comprises a T having in its longitudinal circuit a controllable charging thyristor for setting the magnitude of the electromagnetic supply voltage and a capacitor in its transverse circuit.
The control electrode of the charging thyristor, which advantageously has the shape of a quadrupole, is connected to the input of a setting unit of a program which controls the electromagnetic supply voltage via a voltage conversion control unit.

According to the above shaper, with power supply from an AC power source, variable amplitude pulses can be shaped by phase control of the charging thyristor.

Preferably, another four poles identical to the four poles of the T-shape are connected anti-parallel to the four poles of the T-shape.

This improves the shape of the electromagnetic voltage curve and the input current curve. In one embodiment of the invention, the chiyoke is connected in series with the charging thyristor.

This increases the power factor of the transducer as a whole.

In order to increase the maximum pressure, it is appropriate that the discharge thyristor is controllable, since the voltage phase control is independent of the voltage magnitude. In another embodiment of the invention, the pulse shaper is connected to a source of voltage whose magnitude is equal to the difference between the doubled and stabilized mains voltage and its actual value. Thereby, the pressure can be stabilized by the use of standard voltage stabilizers without changing the control system.

In order to increase pressure stabilization and reduce power consumption by eliminating the voltage stabilizer in the power circuit, a value proportional to the regulated voltage squared of the electromagnetic power supply is set by a value proportional to the actual value of the voltage. It is worthwhile to further incorporate into the device a dividing function generator, the output of which is connected to the control electrode of the charging thyristor to a voltage converter control unit and to a unit that sets the program for controlling the electromagnet supply voltage. It is necessary to pass.

The present invention will now be explained in more detail using examples.

It should be noted that the examples are given for the convenience of explanation to achieve the above-mentioned object, and the scope of the present invention defined in the claims is not limited thereby. As mentioned above, the method proposed here for measuring liquids is particularly advantageous for metallurgical and foundry practices where the problem of increasing the accuracy of measuring conductive liquids or liquid metals is most sought after.

However, the method just described increases the accuracy of measurements of both conductive and non-conductive liquids. In view of the main field of application of the invention, an embodiment will be disclosed later for the case where a conductive liquid is measured by a pressure measuring device.

The apparatus implementing the method is first described. Referring to FIG. 1, a preferred improvement of the apparatus for carrying out the method of the invention is as follows:
It has a container 1 filled with the liquid to be measured, the level of the liquid in the container being designated "h".

The container 1 communicates with a discharge conduit 2 having a discharge opening 3 .
A detector is operatively connected to the discharge conduit 2 for detecting the passage of a liquid flow front through the monitored cross-section of the discharge conduit. The location of the monitored cross section may change for different conditions. Therefore, for a discharge conduit rising at a short steep angle, the monitored cross-section is preferably chosen as close as possible to the discharge opening 3, whereas for a long discharge conduit with a horizontal section, the opening is It is located further away from the discharge opening, preferably in a part that rises at a steep angle. The configuration of the detector 4 is selected with respect to the liquid to be measured and its temperature.

For use as such detectors, photoelectric, inductive,
Capacitive type and float type transmitters are known.
For liquid metal conveyed through ceramic tubing, the best accuracy in detecting when the front of the liquid stream passes through the monitored cross section is achieved with the use of electrical contact detectors. The device also has a system of outlet pipes 5, 6, 7 communicating with each other and further with the container 1 and the discharge conduit 2.

The current in the liquid to be measured is generated by two inductors whose magnetic cores 8, 9 are closed and surround the conduits 5, 7, respectively. Inductor windings 10, 11
is supplied with alternating current. The connection points of conduits 5, 6, and 7 are as follows:
It is surrounded by an electromagnetic core 12 of an electromagnet adapted to generate a magnetic field in the liquid that interacts with the electrical current in the liquid.

The electromagnet has one main winding 13 with two coils connected in series. Capacitor 1 in parallel with main winding 13
4 are connected. The capacitor 14 is connected to the electromagnetic winding 13
Together, they form an LC circuit, the purpose of which will be described later.

The electromagnet also has compensation windings 15, 16 connected in series with the inductor windings 10, 11, respectively.

The compensation winding provides compensation for the magnetic flux generated in the magnetic core 12 by the current in the liquid metal and by the absence of a back emf at the output of the voltage converter 17.

The winding 13 is supplied with current via a voltage converter 17 which acts to vary the electromagnetic supply voltage according to a pressure variation pattern set by the control system.

The control system has a unit 18 for setting the program for controlling the electromagnetic supply voltage and a unit 19 for controlling the voltage converter 17.

According to the invention, the voltage converter 17 is a shaper of the voltage pulses of the LC circuit. the amplitude of the pulse is controlled according to a program of pressure fluctuations in the liquid being measured;
The frequency of the pulse is equal to the frequency of the inductor current. The capacitance of capacitor 14 is selected such that the frequency of free oscillation of the LC circuit is within 1 to 1.5 of the pulse frequency of the pulse shaper output. In a preferred embodiment of the invention, the pulse shaper is a T-shaped four pole whose longitudinal circuit is connected to a charging thyristor 20 (FIG. 2) which acts to set the magnitude of the electromagnetic supply voltage. It has a phase-controlled discharge thyristor 21, while its lateral circuit has a storage capacitor 22.

The operation of the charging thyristor 20 is controlled by a unit 18 which sets the program for controlling the electromagnetic supply voltage, so that the control electrode of the charging thyristor 20 is connected to the voltage converter 1.
It is connected to the input of unit 18 via unit 19 which controls 7. The storage capacitor 22 is charged when the positive half-wave of the sinusoidal alternating voltage acts on the input of the converter 17.

The energy stored in the capacitor 22 is transferred as a short pulse through the discharge thyristor 21 to the capacitor 14.
will be transferred to. This causes sustained oscillation within the LC circuit,
Its frequency is adjusted by the parameters of the LC circuit and is required to be within 1 to 1.5 of the pulse frequency at the shaper output. The amplitude of the oscillation depends on the voltage level at which storage capacitor 22 is charged. This change in level results in a change in voltage at the output of converter 17.
According to one refinement, the pulse shaper has another T-shaped quadrupole, similar to that described above, connected to it in antiparallel.

An improved version of this pulse shaper is shown in FIG. 3, where the components of the additional T-shaped quadrupole are as follows. That is, a charging thyristor 23, a discharging thyristor 24, and a storage capacitor 25. A choke 26 is connected in series with the charging thyristor 20 which acts to limit the rate of rise of current through the charging thyristor 20 when charging the storage capacitor 22 .

In this case, the waveform of the current drawn from the power supply approaches more closely a sinusoidal waveform, which makes it possible to increase the power factor of the pulse-shaped tube. Correct the phase of the electromagnet current,
The discharge thyristor 21 is controllable in terms of controlling the phase of the output voltage across the load with respect to the phase of the supply voltage, thereby making it possible to increase the pressure generated by the measuring device by 10 to 15%. .

Voltage fluctuations in the power supply distort the normal operating conditions of the device and thus lead to undesirable deviations in the mass of the measuring part, which are caused primarily by perturbing the pressure fluctuation program.

According to the invention, in order to increase the accuracy of the measurements, especially in the measurement of small weights (approximately 0.5 Kf), the pulse shaper has a magnitude equal to the difference between the doubled stabilized supply voltage and the continuous supply voltage. It is connected to the output of a voltage source 27 (FIG. 4). A structure having such a structure is shown in FIG. The power supply 27 has a voltage stabilizing device 28 whose input terminals 29 and 30 receive the supply voltage and whose output terminal 31
At and 32, a stabilized voltage having twice the magnitude of the supply voltage is generated. Terminals 29 and 31 are connected to each other, while terminals 30 and 32 are outputs of power supply 27. Since the power introduced by the electromagnet is of the order of 10 KW and the voltage converter is a power amplifier with an amplification factor of more than 100, correction for supply voltage fluctuations is applied to the system controlling the voltage converter 17. It is even more advantageous to be For this purpose, and in order to ensure the constancy of the pressure variation program with varying supply voltages, one of the improvements of the proposed device is to reduce the electromagnetic supply voltage by a value proportional to the actual value of the voltage. It has a function generator 33 (FIG. 5) for dividing a value proportional to the stabilized voltage. Devices that make it possible to obtain input signals for such function generators are well known in the art. The output of the function generator 33 is connected to the control electrodes of the charging thyristors 20 and 23 via a unit 18 for setting the control program of the electromagnet supply voltage and a unit 19 for controlling the voltage converter 17.

The method of the invention can take into account different production requirements for the metering process as determined by the volume of the metering portion, the liquid being metered, etc.

FIG. 6 shows a graph of pressure variation versus time illustrating one of the improvements of the proposed method.

Before the measurement is started, the liquid in the discharge conduit 2 is maintained at an initial level determined by the conditions of the production process.
The electromagnet is then supplied with a voltage which ensures a preset value of the pressure PO and an initial liquid level corresponding to this pressure. Often the initial level of liquid is equal to the level in the container, so that the liquid in the discharge conduit is
It is in hydrostatic equilibrium with the liquid in the container and the electromagnet is supplied with a voltage that produces an applied voltage of zero. At time t1, with the measurement start signal from time t1 arriving at unit 18, said unit port 8 generates signals, according to which the supply voltage of the electromagnet is increased at a constant rate. The configuration of the device implementing the method of the invention provides a correspondence between pressure fluctuations and changes in the supply voltage of the electromagnet predetermined by the program, which will be explained in detail later. This increase in pressure causes the liquid to be metered to flow along the discharge conduit 2 towards the discharge opening 3 .

In the above-described process of pressure increase, the rate of pressure change is chosen constant equal to 0.05-0.1 m/s;
This ensures the completion of the hydraulic transition process associated with the acceleration of the liquid and the change in the level of the measured liquid in the discharge conduit and the electromagnet until the front of the liquid flow passes through the monitored cross-section. provides synchronization between changes in the supply voltage of the conduit so that the metal velocity across the monitored cross-section of the conduit is independent of the metal level in the vessel. The liquid detector 4 is activated at t1 when the front surface of the liquid flow being measured passes through the cross section to be monitored, following which execution of the pressure fluctuation program is started.

According to the invention, the pressure is varied with respect to the pressure P1 reached when the liquid flow front passes through the monitored cross section. According to the modification of the program just described, increasing the pressure at rate 1 is continued for a preset time interval τ1 until time t2, during which time the liquid continues to rise in the discharge conduit 2.

In the time arc, at pressure P2, the liquid reaches the discharge opening 3 and metal discharge from the measuring device begins. As the pressure increases further until P1, which corresponds to time t1, the metal flow rate Q increases to the magnitude Qmax required by the production process.
Increasing the flow rate Qmax is achieved by increasing τ1 and V1. After the end of the time interval τ1, the pressure remains unchanged over the time interval τ2 until time t1. time interval τ
2, the discharge of liquid proceeds under the action of an overpressure equal to the difference P21P2.

The mass of the measurement part is generally determined by a value τ2 set by a program. In a special case, τ2 becomes zero when a smaller measurement portion is spilled. time interval τ
2, a constant rate variation of the voltage of the electromagnet is started, which causes the pressure to decrease at a constant rate V2.

At time t:, the pressure reaches a value of P↓, but since the liquid has a certain inertia, its release continues until the pressure drops to the value of P1 at time t2.

After this, the pressure is reduced to the initial level. The pattern of pressure fluctuations at this stage does not have any effect on the mass of the measuring part, so that after the liquid flow drops below the monitored cross-section of the discharge conduit, the pressure fluctuations follow the same pattern as before. , or executed suddenly. In the refinement of the method just described, the pressure drop continues at a constant rate V2. At time t+, liquid at pressure P1 passes through the monitored cross section. At time t1, the applied pressure becomes zero, after which the hydrostatic equilibrium between the liquid in the discharge conduit 2 and the liquid in the container is established again. At this time, the initial liquid level in the discharge conduit 2 is reduced by a value equal to the drop in the liquid level in the container 1 after discharging the metering part.
lower than the initial level before discharging the measured portion.

From the above description of the method, it can be seen that the speed V2 should be selected such that the liquid discharge ends before the pressure is reduced to the initial level.

In one of the following measurement cycles, due to the drop in the liquid level in the container 1, lifting the liquid to the monitored cross-section requires applying a correspondingly higher pressure P2, which is achieved at time t1. . Therefore, the liquid discharge starts at time T2 at pressure P2 and the pressure rise is P
Proceed to the value of 2 and end in the time bow. The ejection at pressure P: is completed by time T2, followed by the start of pressure reduction at a constant rate V2 to the initial level, and the liquid ejection ends at time T2 at pressure P2. The difference between the level of the cross-section to be monitored and the level of the discharge opening, the soil rise rate of pressure V,,
and the time interval for liquid rise from the monitored cross-section to the discharge opening ( T2-t1) is the same for all measurement cycles, ie t1-t1=T2.

Therefore, the value of the maximum overpressure (P3-P2) is also the same for all cycles. Therefore, the average pressure is also constant during the controlled release stage, defined as the ratio of the area S of the trapezoid 1-2-3-4 to the time interval (T4-T2) during the controlled release stage, which is also constant. It is.

Obviously, the above equation has only the initial metal level and time-independent quantities (the time interval (T2-t1) is
is shown above to be constant for a given value V1).

The constancy of the overpressure and its rate of fall provides a constancy of the liquid velocity when the overpressure is zero for all measurement cycles.

This rate is initial for the phase of inertial release, and since the pressure decreases at the same rate, the inertial release will occur over the same time at a pressure difference (P2-P4) that is constant with respect to pressure P2. It should end for (T6-T5), ie the average pressure acting on the metal during the phase of inertial ejection is likewise constant for every cycle.
This point is obvious, but as before it can be proven by solving the differential equations of the appropriate system. The constancy of the pattern of change in the pressure difference acting on the metal over every measurement cycle, and the constancy of the initial metal velocity as it passes through the monitored cross-section, dictates the constancy of the mass of the metal release during the cycle, i.e. It gives an independence of the discharge time τ3 of the metal from the metal level in the vessel and the conduit and the measured partial mass. At the same time, the magnitude of the initial metal level in the discharge conduit can substantially influence the production conditions of the metrology process.

Therefore, when measuring alloys that are easily oxidized (such as magnesium), in every cycle,
The return of metal in the discharge conduit 2 to the level within the vessel increases the risk of contamination of the metal by oxidation products that remain on the walls of the conduit after any descent of the metal. Cross section to be monitored (t1-
The varying duration of metal rise from the initial level to TO) lengthens the overall counting cycle time as the metal is released from the container, which in some cases hinders process automation and also reduces its output. decrease. In such cases, it is practical to maintain the metal in the discharge conduit 2 at a constant level with respect to the discharge aperture 3, albeit with some additional power consumption.

This problem is solved by reducing the pressure P5 reached when the liquid drops below the monitored cross-section by a predetermined value.

The same result is achieved when the rate of pressure drop V2 is maintained for a preset time after passing the monitored cross-section (FIG. 7).

ΔPOp5-P62v2(T7-T6) where P6 is the initial pressure for all measurement cycles except the first, T7-T6-CONst. and therefore Δp=CONst. It is.

The drop in the liquid level in the conduit for all cycles proceeds under the influence of the same pressure difference ΔP=V2(t-T6), where t is the running time. Therefore, the liquid during all cycles reaches the monitored cross section with the same pressure difference (P2-P5); when the metal passes through the monitored cross section, the pressure reached decreases by some constant value. When the liquid is in equilibrium at approximately the same level with respect to the monitored cross-section (i.e. a pressure P6 similar to pressure P1 increases as the container empties, but the pressure difference (
P1-P6) remains constant. Since, with respect to the monitored cross-section, the liquid level in the discharge conduit 2 remains constant, the time to fill the discharge conduit up to the monitored cross-section (t1-TO) also remains constant and thus the overall The measurement cycle time T8-t1 is also constant. In implementing the above method, a first counting cycle is started as in the example described above, ie at a metal level in the discharge conduit 2 equal to its level in the container 1.

a predetermined constant level of metal in the discharge conduit 2 with respect to the discharge opening 3 begins automatically at the end of the first counting cycle and is automatically maintained constant until discharge from the container 1 is completed; Thereafter, the metal level in the container 1 must be reduced. This reduces overall power consumption and also reduces clogging of the discharge conduit by metal oxidation products. In the measuring device now being described, the relationship between the supply voltage of the electromagnetic system and the generated pressure is given by the following equation.

P=KlUlU2 where k1 is a constant proportionality factor, U1 is the voltage of the current induction system and U2 is the voltage of the flux generation system.

On the other hand, U1=K2U3 U2-K3fU3 where U3 is the main voltage, K2, k3 are the proportional factors, and f is the time function of the electromagnet voltage change over the cycle.

From the above, P=Klk2k3fU: (9).

Variations in the mains voltage cause variations in the actual pressure produced by the pump, which affects measurement accuracy.

It is clear that with an additional correction in the form of U3 (where U3N is the stabilized value of the mains voltage) then crystal-b-UIゞ3N'-'.

For relatively small pressure fluctuations, correction is made in the form of a simplified approximation function;

Since the voltage deviation is small (less than 10%), the pressure deviation with such a correction does not exceed 1%.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a device constructed according to the present invention, FIG. 2 is a diagram showing a circuit of a modified voltage converter, and FIG. 3 is a diagram showing a circuit of another modified voltage converter. , FIG. 4 shows a modification of the voltage converter connection, FIG. 5 shows a modification of the control system connection to the voltage converter constructed according to the invention, and FIG. 6 shows one of the methods of the invention. FIG. 7 is a pressure versus time curve illustrating a variation of the method of the invention; FIG. 1... Container, 2... Release conduit, 3...
...Liquid detector, 5, 6, 7... Channel conduit system, 8, 9... Inductor magnetic core, 10
, 11... Inductor winding, 13...
Electromagnet main winding, 14... Capacitor, 15, 1
6...Compensation winding, 17...Voltage converter, 18...Unit for electromagnet voltage control program setting, 19...For voltage converter control Unit, 20... Charging thyristor, 21...
・Discharge thyristor, 22...Storage capacitor, 26...Charge, 27...Power supply, 33...Function generator.

Claims (1)

[Claims] 1. A method for measuring liquid over time using a pressure measuring device, the method comprising: raising the liquid in a discharge conduit by increasing the pressure from an initial level at a measurement start signal; , detecting the point at which the front surface of the liquid stream passes through one monitored cross-section of the discharge conduit, and directing the liquid under the action of a pressure varied by a predetermined program, from which point the execution of the program is started. A method for measuring liquid over time using a pressure measuring device, comprising steps of releasing and then decreasing the pressure, the increase in pressure increasing until the front of the liquid stream passes through the monitored cross section. is carried out at a constant rate such that the velocity of the liquid stream is constant, and varying said pressure by a predetermined program is done with respect to the pressure reached at the point when the front of the liquid stream passes through the monitored cross section. and the reduction in pressure is performed at a constant rate until the liquid in the conduit drops below the monitored cross section, the rate of each pressure change remaining constant throughout the measurement cycle. A method for measuring liquid over time using a pressure measuring device characterized by the following. 2 Varying the pressure according to the predetermined program maintains a rate of increase in pressure during a first time interval whose length is determined by the required liquid flow rate and thereafter whose length is determined by the volume of the metering part. 2. A method according to claim 1, characterized in that the pressure is maintained constant during the second time interval in which the pressure is determined. 3. Starting from the point of descent of the liquid below the monitored cross-section of the discharge conduit, the pressure reached at this point is reduced by a predetermined amount. The method described in Section 2. 4. A method according to claim 3, characterized in that starting from the point at which the liquid falls below the monitored cross-section of the discharge conduit, the rate of pressure reduction is maintained for a predetermined period of time. . 5 Under conditions of voltage fluctuations in the power supply, one system serves to generate an electric current in the liquid, and the other system serves to generate a magnetic field in the liquid that interacts with the current in the liquid. If conductive liquids are to be measured by an electromagnetic pump with an electromagnetic system, it is important to maintain the same rate of pressure change throughout the measurement cycle at a power supply voltage of the square of the power supply voltage. 2. A method according to claim 1, characterized in that it is carried out by supplying a voltage having a magnitude equal to the ratio to the value to an electromagnetic system serving to generate a magnetic field in the liquid. 6 Equipped with two electromagnetic systems, one serving to generate a current in the liquid and the other serving to generate a magnetic field in the liquid that interacts with the current in the liquid, under conditions of voltage fluctuations of the power supply. When conducting liquids are being measured by electromagnetic pumps, it is important to keep the rate of pressure change constant throughout the measurement cycle, which is equal to twice the stabilizing voltage of the power supply and the actual power supply. 2. A method according to claim 1, characterized in that it is carried out by supplying a voltage with a magnitude equal to the difference in value to an electromagnetic system serving to generate a magnetic field in the liquid. 7 Raising the liquid in the discharge conduit by increasing the pressure from the initial level at the start signal of the measurement, detecting the point in time when the front of the liquid flow passes through one monitored cross-section of the discharge conduit, and determining the point of said passage. A device for measuring liquid over time using a pressure measuring device, comprising steps of ejecting liquid under the action of a pressure varied by a predetermined program whose execution starts from , and then decreasing said pressure. and the pressure is increased at a constant rate such that the velocity of the liquid stream is constant by the time the front of the liquid stream passes through the monitored cross section, and the pressure is increased by a predetermined program. The varying is done with respect to the pressure reached at the point at which the liquid flow front passes the monitored cross section, and the reduction in pressure is such that the liquid in the conduit falls below the monitored cross section. A device for measuring liquid over time, in which the rate of change in each pressure is maintained constant throughout the measuring cycle, in which a discharge conduit 2 filled with the liquid to be measured, channel conduits 5, 6 in communication and with the container 1 and the discharge conduit 2;
, 7, whose closed magnetic core 8, 9 surrounds one of the conduits 5, 7, serving to generate an electric current in the liquid;
The windings 10, 11 also have at least one inductor to which alternating current is supplied, and the connection points of at least two conduits control a unit 18 for setting a program for controlling the electromagnetic supply voltage and a voltage converter 17. At least one capacitor 14 connected in parallel is supplied with current through a voltage converter 17 adapted to vary the electromagnetic supply voltage according to a pressure variation pattern set by a control system with a unit 19 for 1 main winding 1
3 and compensation windings 15, 16 whose number is equal to the number of inductors and connected in series with the inductor windings 10, 11.
an electrically conductive liquid detector 4, having a liquid detector 4, surrounded by electromagnets serving to generate a magnetic field in the liquid that interacts with the electric current in the liquid, and further comprising a liquid detector 4 mounted on the monitored cross-section of the discharge conduit 2. In the device for the case where liquids are measured, the voltage converter 17 is a pulse shaper of the voltage of the LC circuit formed by the electromagnet and the capacitor 14, the amplitude of the pulses being controlled according to the pressure fluctuation program, the pulse is equal to the frequency of the inductor current, and the capacitance of the capacitor 14 is such that the free oscillation frequency of the LC circuit is 1 to 1.5 times the pulse frequency at the pulse shaper output.
Apparatus for measuring fluid over time, characterized in that the device is selected to be within the range of: 8. The pulse shaper has a longitudinal circuit having a controllable charging thyristor 20 for setting the magnitude of the electromagnet supply voltage and a discharging thyristor 21 for controlling the phase of the voltage, while its lateral circuit has a storage capacitor 22. The control electrode of the charging thyristor 20 has a T-shaped four-pole shape.
Claim 7, characterized in that it is connected via a unit 19 for controlling a voltage converter to the input of a unit 18 for setting a program for controlling the electromagnet supply voltage.
The equipment described in section. 9 Another 4 poles identical to the 4 poles of the T-shape are connected to the 4 poles of the T-shape.
9. Device according to claim 8, characterized in that it is connected anti-parallel to the poles. 10. Device according to claim 8 or 9, characterized in that the choke 26 is connected in series with the charging thyristor 20. 11. The device according to claim 8, 9 or 10, characterized in that the discharge thyristor is controllable. 12. Any one of claims 7 to 11, characterized in that the pulse shaper is connected to a voltage source 27 whose magnitude is equal to the difference between twice the supply voltage and the actual supply voltage. The device described in. 13 further comprising a function generator 33 for dividing the value proportional to the stabilized voltage of the square of the electromagnet's power supply by a value proportional to the actual value of the voltage, the output of the function generator 33 being the electromagnet's supply voltage. Claim 8, characterized in that it is connected to the control electrode of the charging thyristor 20 through a unit 18 for setting a program for controlling the voltage and a unit 19 for controlling the voltage converter 17. equipment.