RU2138028C1 - Device measuring level and density - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: device can be used to measure level and density of oil products and other fluids in tanks during their taking in, issue and storage. Device measuring level and density has two floats of different buoyancy with permanent magnets mounted for movement along acoustic line. Acoustic line is manufactured in the form of string from magnetostrictive material. Damper is installed on one end of acoustic line, reading coil is located under it. Immobile permanent magnet is positioned at fixed distance from reading coil. Lower density float has lower part made in the form of cylinder with axial hole and upper part made of bars arranged on cylinder butt at equal spacing along length of its circumference. Upper float is mounted for movement between bars of lower float. Device also includes conversion unit connected to ends of acoustic line and reading coil. All actions of device are initiated through exchange bus by instructions from microcomputer. EFFECT: increased accuracy and simplified design of device. 3 dwg

Description

 The invention relates to the field of measuring technology, automation and computer technology and can be used in systems for measuring the level and density of petroleum products and other liquids in tanks during tempering, reception and storage.

 Many devices are known for measuring the level or density individually. For example, a device for measuring fuel level (see US patent N5076100, G 01 F 23/00, 1991) contains a sound pipe of magnetostrictive material with a damper at one end, a read coil installed in front of the damper, three permanent magnets, one of which are fixed at the end of the sound pipe from the side of the read coil, and the other two are located on the floats, an amplifier-driver, a pulse generator and a counter. This device allows you to measure two levels of liquids with different densities.

 The closest in technical essence to the proposed device for measuring the level and density is a device for measuring the level and density of petroleum products (RF patent N 2047845 G 01 F 23/30 1995).

 The specified device contains a multiprocessor controller, measuring pulleys and pulleys with a counterweight, counters in the form of perforated disks and optical displacement sensors, multi-link articulated block. The float is made with a hole in which the upper part of the displacer is installed with the possibility of movement. The displacer and the float are connected to the corresponding measuring pulley via a moving element, and the microprocessor controller is connected to optical displacement sensors mounted on the corresponding measuring pulley.

 The disadvantages of the known solutions include a rather complex kinematic design, low accuracy and low performance.

 The problem to which the invention is directed, is to increase the accuracy and simplify the design of the device for measuring the level and density of liquids.

 The problem is solved by additional introduction to the known device, which contains a sound duct installed in a protective casing in the form of a string of magnetostrictive material with a damper at its first end, a read coil installed under the damper, and a first permanent magnet located under the read coil, a second float with a second permanent magnet mounted under the first permanent magnet, with the possibility of movement along the sound duct, and the first float contains a third permanent magnet It is located between the second float and the second end of the sound duct with the possibility of moving along the sound duct, the lower part of the first float is made in the form of a cylinder, and the upper one contains n rods located at the end of the cylinder with the same pitch along the circumference of the cylinder, where n ≥ 2, the second float installed with the possibility of free movement between the rods of the first float, the conversion unit includes an amplifier-driver, the inputs of which are connected to the outputs of the read coil, the pulse generator and counter, regis memory, register with parallel input and sequential shift of information, two shapers of start pulses, address decoder, shaper of ready signal, shaper of blocking pulses, two keys, the input of the first of which is connected to the second end of the sound duct and the input of the second to the first end of the sound duct and exchange bus, the output of the amplifier-driver is connected to the clock input of the register with a parallel input and a sequential shift of information, the output of the first driver pulse train is connected to the reset input a counter, the counter input of which is connected to the output of the counter pulse generator, the information output of the counter through the memory register is connected to the exchange bus, which is connected to the input of the address decoder, the first output of which is connected to the enable input of reading the memory register, the second and third outputs of the address decoder are connected respectively to the input of the first trigger pulse shaper and the second input of the ready signal shaper, the first input of which is connected to the recording register enable input and the register output Trace with parallel input and sequential shift of information, the fourth output of the address decoder is connected to the input of the register selection code record with parallel input and serial shift of information, the parallel input of which and the output of the ready signal generator are connected to a common bus, the control inputs of the first and second keys are connected respectively to outputs of the first and second triggering pulsers, and outputs with a common bus, inputs of the second triggering pulser and blocking pulser the ki are connected respectively to the fifth and second outputs of the address decoder, and the output of the blocking pulse shaper is connected to the register blocking input with inputs for parallel input of information, and a sequential shift of the information, the sound duct at a point located between the first magnet fixed at a fixed distance from the read coil, and a read coil connected to a power source.

 Figure 1 - shows a functional diagram of the device.

 The device comprises a sound duct 1 installed in a protective casing 22 made of magnetostrictive material in the form of a string with a damper 3 at the first end, permanent magnets 4, 5 and 6, one of which 6 has a fixed distance B to the read coil 7, and the other two are located on different floats buoyancy (floats of level 20 and density 21), two keys 2 and 9, amplifier former 8, two former 14 and 15 start pulses, register 10 with parallel input and sequential shift of information, generator 11 counting pulses, counter 12, register 13 p memory, address decoder 16, ready signal shaper 17, exchange bus 18 and blocking pulse shaper 19. Moreover, one end of the sound pipe 1 is connected to the input of the key 2, and the second through the damper 3 with the input of the key 9, the outputs of the keys 2 and 9 are connected to the common bus, and the control input of the key 2 is connected to the reset input of the counter 12 and the output of the first driver 14 of the start pulses the input of which is connected to the second output of the address decoder 16 and the input of the blocking pulse generator 19, the output of which is connected to the blocking input of the register 10 with parallel input and serial shift of information, an input for parallel input of information, the input of which is dinan with exchange bus 18, and the input of the selection code record with the fourth output of address decoder 16, the output of register 10 with parallel input and sequential shift of information is connected to the write enable input of memory register 13 and the first input of the ready signal generator 17, the output of the counting pulse generator 11 connected to the counting input of the counter 12, and the information output of the counter 12 through the memory register 13 is connected to the exchange bus 18, the first output of the address decoder 16 is connected to the write enable input of the memory register 13, the third output is sec m the input of the ready signal generator 17, the input of the address decoder 16 and the output of the ready signal generator 17 are connected to the exchange bus 18, the fifth output of the address decoder 16 is connected to the input of the second trigger pulse generator 15, the output of which is connected to the control input of the key 9, the outputs of the read coil 7 connected to the inputs of the amplifier-driver 8, the output of which is connected to the clock input of the register 10 with parallel input and sequential shift of information.

 A device for measuring level and density works as follows. All actions of the device are initiated via the bus 18 exchange by commands of the microcomputer. Two operating modes are distinguished: a mode for determining the position of magnets (4, 5 - movable floats and 6 - a fixed magnet), which is launched through the second output of the address decoder 16 by the first driver 14 of the start pulses and key 2, and the second mode is the magnetization of the read coil 7, which is triggered through the fifth output of address decoder 16 by the second driver 15 of start pulses and key 9. As can be seen from the diagram, the bias current in the second mode flows along the circuit: +12 V power supply, end of sound duct 1 from damper 3, key input 9, common bus. This circuit has a minimum and constant length of the sound duct, which allows you to have the maximum possible bias current. In the first mode, the excitation current of the ultrasonic wave flows through the circuit: +12 V power supply, the end of the sound pipe 1 opposite from the damper 3, key 2 input, common bus. In this case, the length of the sound duct is variable and depends on the size of the tanks.

 Consider the operation of the device in the first mode in more detail. On command from the microcomputer, the signal from the fourth output of the address decoder 16 to the register 10 records the selection code for the exchange bus 18, which determines the measured interval proportional to one of the segments XI, X2, (2A-B). A is the distance from the read coil to the second end of the sound duct. From the magnet 6, fixed next to the reading coil 7 at a distance B from it, an ultrasonic signal reflected from the second end of the sound duct is passed, the distance (2A-B). And from magnets 4 and 5 located on floats of different buoyancy, direct ultrasonic signals that have passed the distances X2 and XI, respectively, are received. According to another command from the microcomputer, the signal from the second output of the address decoder 16 is used to start the first operation mode of the device. The first driver 14 of the start pulses resets the counter 12 to zero and opens the key 2, thus creating a current pulse in the sound pipe 1, as a result of which a circular magnetic field is formed around it, which interacts with the longitudinal fields of the permanent magnets 4, 5 and 6. As a result the interaction of these magnetic fields, due to the direct magnetostrictive effect, in the sound duct 1 at three points of the location of the permanent magnets, ultrasonic waves arise, which propagate in both directions. Ultrasonic waves directed to the opposite end of the sound pipe 1 from the damper 3 are reflected from it and move to the other end. The waves passing through the reading coil 7, due to the inverse magnetostrictive effect, are converted into electric pulses spaced in time. Thus, on the read coil 7, 6 pulses from three magnets arise: 3 — direct and 3 — reflected from the first end of the sound duct 1. Further, all ultrasonic waves are absorbed by the damper 3. The first direct pulse from magnet 6 falls into the blocking zone and is not used, and the remaining 5 pulses can be received in the register 10. The blocking zone is formed by the shaper 19 by applying a pulse to the clock input of the register 10 to exclude its false operation from the noise created by the excitation current pulse in the sound pipe 1. The start pulse and the driving duration shorter lock pulse. Five electrical pulses from the amplifier-driver 8 are sequentially fed to the clock input of register 10, from which selection code was recorded in register 10, the signal will appear at its output after the arrival of the first, second, or fifth clock pulse. Consider these pulses corresponding to direct ultrasonic waves from 5 and 4 magnets of the floats, as well as the pulse reflected from the end of the sound duct 1 of the ultrasonic wave of magnet 6.

In order for the signal after the first clock pulse to appear at the output of register 10, you must enter the selection code 011111 in register 10, after the second clock-001111 and after the fifth - 000001. As a result of the appearance of the signal at the output of register 10, the digital code from counter 12 corresponding to the distance
K _x1 = FX ₁ / V; K _x2 = FX ₂ / V, K _(2A-B) = F • (2A-B) / V,
where V is the velocity of propagation of the ultrasonic wave;
F is the frequency of the generator 11 counting pulses;
X1, X2, (2A-B) are the distances to the read coil 7 traveled by ultrasonic waves from magnets 4, 5, 6.

 According to the signal from the third output of the decoder 16 and the presence of a signal at the output of the register 10, the driver 17 issues a readiness signal for the device data to the exchange bus 18. At the command of the microcomputer, a signal from the first output of the address decoder 16 is allowed to read data from the memory register 13. Thus, in one operation cycle, one of the distances X1, X2, or (2A-B) is measured, and their interrogation frequency is determined by the microcomputer algorithm.

The calibration value of the reference point code K _{(2A-B) is} proportional to the distance (2A-B) and changes slightly over time. The polling frequency of this point can be quite low, and the polling frequency of the other two points will depend on the selected algorithm of the statistical method for processing code values.

After receiving the codes K _x1 , K _x2 and K _{(2A-B), the} microcomputer calculates the values of X1 and X2 according to the formulas:
X1 = (2A-B) • K _x1 / K _(2A-B) and
X2 = (2A-B) • K _x2 / K _(2A-B)
(2A-B) -scale factor.

где m - масса поплавка плотности, определяется взвешиванием;
V - объем вытесненной эталонной жидкости, вычисляется при измерении ρ_эт ареометром, где

S - площадь сечения верхней (погруженной) части поплавка плотности, определяется обмером поплавка;
Δh -h_эт -h_изм - изменение расстояния между двумя поплавками в жидкостях с эталонной и измеряемой плотностью.The presence of the calibration value K _(2A-B) in the formula allows automatic compensation of the influence of destabilizing factors. The difference (X1 - X2) - should be a constant with a constant liquid density. When the density of the liquid changes, the distance X1 (float level 20) does not change, and X2 (float density 21) is proportional to the density. Thus, by measuring with a hydrometer the density of the reference liquid ρ _et and using a device for measuring the level and density, the distance between the two floats:
h _et = X _1et -X _2et ,
where X _1et and X _2et are the distances to the floats in the reference fluid, it will be possible to determine the density of another fluid by the formula:

where m is the mass of the density float, determined by weighing;
V - volume of liquid displaced by reference, is calculated by measuring ρ _fl hydrometer, wherein

S - sectional area of the upper (immersed) part of the density float, determined by measuring the float;
Dh -h -h _{fl ism} - the change in distance between the two floats in the fluids of the reference and the measured density.

The distance between the two floats is calculated by the formula:
h = _ism X1izm - X2izm.

 The product S • Δh can be positive or negative depending on the increase or decrease in the measured density compared to the reference.

 A necessary requirement for a density float is to maintain a constant mass throughout the entire operating time. To maintain a constant mass of the density float, it is necessary to use materials for their manufacture with a minimum percentage of liquid suction, for example spheroplasts.

The most important point is the design of the density float, which provides not only operability, but also the necessary accuracy. The design of the density float is influenced by both the design of the level measuring device (the diameter of the pipe in which the sound pipe is pulled, the diameter of the level float) and the required working stroke of the density float. In FIG. 2 shows floats of density 21 and level 20, and in FIG. 3 - constructive placement of the elements of the device. The density float 21, as it were, consists of two parts: the lower one, which determines the main volume and weight of the float, and the upper one, for example, consisting of 4 rods and which determines the increment of the volume ΔV relative to the reference volume of the float immersion. The operating state of the float is a completely submerged lower part and partially submerged rods depending on the density of the product (according to the principle of a hydrometer). The more rods are immersed, the lower the density and, conversely, the less immersed - the higher the density. The internal distance between the rods should be such that the level 20 float can freely, without touching the rods, move along them and the pipe along with the level, forming the distance between the two floats h _et and h _meas . The floats are made with axial holes in which the sound duct is installed in the protective casing.

The distance between the minimum and maximum locations of the two floats forms the working stroke of the density float. The stroke is selected from the condition of the measuring range. So, if it is necessary to measure the density of an oil product in the range of 700 - 800 kg / m ³ (i.e., Δρ _meas = 100 kg / m ³ ), then with a weight of a density float of 0.6 kg, the volume change is ΔV = 100 cm ³ . Or, in other words, when the density of the product changes by 1 kg / m ^{3, the} volume will change by 1 cm ³ with the corresponding sign. If we take the cross-sectional area of four rods equal to 1000 mm ² (each rod with D = 17.84 mm), then h _meas = 1 mm. It follows that, with a measuring range of 700 - 800 kg / m ^{3, the} stroke of the density float will be 100 mm. The density measurement range for the respective petroleum products can be selected by changing the mass of the float using interchangeable weights, which are installed in its lower part.

With the introduction of weights, the stability of density floats also improves. At the same time, varying the diameter of the rods and their number, you can change the sensitivity of the float or, in other words, the price of the division of the stroke. Taking into account the practically achieved accuracy of measuring the difference h _meas ± 1 mm, it is possible to obtain a density measurement accuracy of ± 1 kg / m ^{3 for the} float embodiment described above.

Claims (1)

 A device for measuring the level and density of a liquid, comprising a first float mounted for movement, and a conversion unit with an indicator, characterized in that it contains a sound pipe installed in a protective casing in the form of a string of magnetostrictive material with a damper at its first end, a read coil installed under the damper, and a first permanent magnet located under the read coil, a second float with a second permanent magnet mounted under the first permanent magnet, with the possibility movement along the sound duct, the first float containing a third permanent magnet and located between the second float and the second end of the sound duct with the ability to move along the sound duct, the lower part of the first float is made in the form of a cylinder, and the upper one is located at the end of the cylinder with the same pitch along the circumference of the cylinder n rods, where n ≥ 2, the second float is installed with the possibility of free movement between the rods of the first float, the conversion unit includes an amplifier-driver, input which are connected to the outputs of the read coil, a pulse generator, a counter, a memory register, a register with parallel input and sequential shift of information, two shapers of start pulses, address decoders, a shaper of a ready signal, a shaper of locks, two keys, the input of the first of which is connected to the second the end of the sound duct, and the input of the second is connected to the first end of the sound duct, and the exchange bus, the output of the amplifier-former is connected to the clock input of the register with a parallel input and sequential shift m of information, the output of the first trigger pulse generator is connected to the counter reset input, the counter input of which is connected to the output of the counter pulse generator, the counter information output through the memory register is connected to the exchange bus, which is connected to the input of the address decoder, the first output of which is connected to the read permission input the memory register, the second and third outputs of the address decoder are connected respectively to the input of the first trigger pulse shaper and the second input of the ready signal shaper, trans the output of which is connected to the enable input of the register of the memory register and the output of the register with parallel input and sequential shift of information, the fourth output of the address decoder is connected to the input of the write code of the register selection with parallel input and serial shift of information, parallel inputs for input of which information and the output of the signal shaper readiness connected to a common bus, the control inputs of the first and second keys are connected respectively to the outputs of the first and second pulse shapers start and the outputs are with a common bus, the inputs of the second trigger pulse generator and the blocking pulse generator are connected respectively to the fifth and second outputs of the address decoder, and the output of the blocking pulse generator is connected to the register blocking input with parallel input and serial shift of information, the sound pipe at the point located between the first magnet, fixed at a fixed distance from the read coil, and the read coil, connected to a power source.

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