RU2777291C1 - Ball flow meter for electrically conductive liquid - Google Patents

Abstract

FIELD: flow meters.

SUBSTANCE: ball flow meter of an electrically conductive liquid consists of a cylindrical body, a helical flow guide apparatus, an annular channel and a ball with zero buoyancy in a liquid, made of a dielectric material, four electrodes. Its electronic circuit contains two operational amplifiers, on which two inverting algebraic voltage adders are implemented, the inputs of which are connected to a reference voltage source and the output of an adjacent adder.

EFFECT: extremely wide dynamic range of measurement, ensuring the operability of the flowmeter at very low liquid flow rates with guaranteed suppression of the influence of electrical and electromagnetic interference, high squareness of the pulsed output voltage, reducing the likelihood of electrochemical processes in the flowmeter, two functionally identical circuit outputs with a very low output resistance, the possibility of using differential output signal, extremely low voltages between the electrodes.

1 cl, 3 dwg

Description

The invention relates to measuring technology and can be used in flow measurement of electrically conductive liquids in the chemical, food and pharmaceutical industries, in housing and communal services, heat and power industry, in heat meters with a water heating system.

Especially promising is the use of the claimed spherical flow meter of an electrically conductive liquid (hereinafter referred to as SHREZh) if it is necessary to record extremely low liquid flow rates and in a very wide dynamic range of measurement, when known electromagnetic, turbine, vortex or Coriolis flow meters cannot be used.

All known designs of ball flowmeters are united, firstly, by the use of a tangential or helical flow guide apparatus and a ball made of a ferromagnetic material or a dielectric that can rotate in an annular channel, and secondly, the use of one or another method of converting the angular velocity of rotation of the ball into frequency output pulse voltage.

The technical and operational characteristics of ball flowmeters must comply with the "General Specifications" [Tachometric ball flowmeters GSP, GOST 14012-76, publishing house of standards, 1984].

Known ball primary transducers of the flow of liquids, which use a magnetic induction sensor of the speed of the ball, made of ferromagnetic material [Kremlin P.P. Flowmeters and counters of quantity. Directory. 4th ed. L.: Mashinostroenie, 1989-701 p.].

Known ball flow transducer [patent RU 2253843 C1, IPC G01F 1/06, publ. 06/10/2005], consisting of a body of non-magnetic material, a restrictive sleeve, an open annular cavity with a ball and a signal pickup unit. The open annular cavity is formed by the inner surface of the housing and the outer surface of the limiting sleeve. The transducer housing on the side of the opening of the cavity with the ball placed in it has an annular recess, which stabilizes the rotation of the vortex flow.

Known ball flow meter [and.with. SU 1591618 A1, IPC G01F 1/06, G01F 1/10, publ. 05/27/1988], consisting of a housing with inlet and outlet pipes. Inside the housing, a displacer rod and a limiting annular element are coaxially located, which forms a non-flowing cavity in the housing with a ball placed in it. The latter is connected with the flow part by an annular slot. In the area where the ball is placed on the body, there is a signal pickup unit. To set the ball into rotation, a jet guide is used, made in the form of tangential channels located in an annular protrusion located at the end of the restrictive annular element from the side of the flow part of the housing.

Known ball flow meter [and.with. SU1117448 A, IPC G01F1/06, publ. 10/07/1984], containing a measuring section of the pipeline with a primary converter located in it, consisting of a cylindrical body with an annular channel, a jet guide apparatus, a jet straightener and a ball, a narrowing device installed coaxially in front of the primary converter and a bypass channel for part of the flow, and also an electrical signal pickup unit.

In all designs of the above ball converters of the liquid flow rate into a pulsed electrical output signal, there are disadvantages due to the use of a ferromagnetic ball and a magnetic induction sensor:

- when a ferromagnetic ball passes near the magnetic circuit of the magnetic induction sensor, it becomes magnetized (attracted) and, with a small flow rate of liquid, it sticks, which causes a non-linearity of the static characteristic and a significant threshold of sensitivity in the region of low flow rates;

- in the horizontal position of the transducer, since the ferromagnetic ball is heavy relative to the weight of the displaced liquid, that is, it has negative buoyancy, there is an inconsistency in the speed of rotation of the ball within one revolution, which increases with a decrease in the rotation speed, which ultimately distorts the static characteristic of the primary transducer even more;

- very strong dependence of the output signal of the magnetic induction sensor on the speed of the ball;

и увеличивает погрешность измерения расхода жидкости

. В частности, серийно выпускаемые шариковые первичные преобразователи «Шторм-8А» и «Шторм-32М», внесённые в Государственный реестр средств измерений под №5706-08, имеют узкий рабочий диапазон (4÷6) и большую погрешность измерения (1,5-2,5%), согласно ТУ 4213-865-00225555-2007.- the use of a heavy ferromagnetic ball and the use of a magnetic induction method for generating an output pulse signal sharply reduces the dynamic range of liquid flow measurement

and increases the measurement error of liquid flow

. In particular, mass-produced ball primary transducers "Storm-8A" and "Storm-32M", entered in the State Register of Measuring Instruments under No. 5706-08, have a narrow operating range (4÷6) and a large measurement error (1.5- 2.5%), according to TU 4213-865-00225555-2007.

Known electro-optical ball primary fluid flow transducer [patent RU 2548055 C1, IPC G01F 1/06, publ. 04/10/2015] in two design versions, consisting of a body with an annular channel in which the ball can freely rotate, a jet guide and a unit for generating an output electrical signal, and a light emitter is used to generate an output electrical (frequency or number-pulse) signal and a photodetector interconnected by direct optical and reverse positive electronic bonds. But this type of ball flow sensor is only suitable for measuring the flow of transparent liquids.

Known radio ball primary fluid flow transducer [patent RU 2685798 C1, IPC G01F 1/05, publ. 04/23/2019], characterized in that the ball is made hollow, in the inner cavity of which there is an inductance in the form of several spatially located turns of an electric wire and a capacitor connected in series and in a ring with a resonant frequency equal to the frequency of self-oscillations of an inductive-capacitive generator with an inductance, located close to the annular channel, the voltage on which, after being detected by the amplitude detector, is the output electrical signal.

Known ball primary transducer flow conductive fluid [patent RU No. 2471154 C1, IPC G01F 1/05, 27.12.2012,], consisting of a cylindrical body with an annular channel in which the ball can freely rotate, a fixed jet guiding apparatus and an electrical signal pickup unit , which differs from a ball primary fluid flow transducer with a magnetic induction sensor and a ferromagnetic ball in that the ball is made of a dielectric material with zero buoyancy in the liquid, and in the area of the annular channel, perpendicular to the ball rolling trajectory, through bushings and flush with the channel surface, two electrodes are located , due to which the converter is operable at low fluid flow rates and in a horizontal position of the housing. However, this design of the transducer does not take into account the influence of the angular velocity of liquid rotation in the annular channel on the mobility of positive and negative ions of the liquid, which reduces the dynamic range of measurement and increases the error in converting the liquid flow rate into the output signal.

Known ball primary transducer flow conductive fluid [patent RU 2566428 C1, IPC G01F 1/06, publ. October 27, 2015, bul. No. 30], consisting of a body made of a dialectical material with an annular channel, a jet guide apparatus and an output electrical signal generation unit, in which a dielectric ball with zero buoyancy in a liquid is used, three electrodes are installed in the annular channel and in the rolling plane of the ball, from in which the middle electrode is connected to the output of the operational amplifier, and the other two electrodes are connected to the inverting and non-inverting inputs of the same operational amplifier, so that the electrical resistances of the liquid between the middle and other two electrodes, together with two auxiliary resistors, form a negative and positive feedback covering the operational amplifier and driven by a rotating ball.

The closest in design and achieved technical result is a ball flow meter conductive liquid [patent RU 2762946 C1, IPC G01F 1/05, publ. December 24, 2021, bul. No. 36], consisting of a cylindrical body, a helical jet guide apparatus with a hub coaxially installed in it, an annular channel between the hub and the inner surface of the body, a ball that can rotate in the annular channel, made of a dielectric material and having zero buoyancy in a liquid, four electrodes , installed at the vertices of the square, two of which, located along the direction of movement of the fluid with the ball, are connected to a common circuit bus, the other two electrodes are connected to the inverting and non-inverting inputs of the single-threshold comparator.

In this design of the flow meter at high liquid flow rates and, consequently, high speeds of the ball relative to the electrodes, suppression of the influence of changes in the mobility of the ions of the electrically conductive liquid on the selected mode of operation of the electronic circuit is achieved. This effect allows you to increase the dynamic range of liquid flow measurement and reduce the error in converting liquid flow into a pulsed output signal.

The disadvantage of this flow meter is the impossibility of maintaining its performance at extremely low fluid flow rates, at which the rotational speed of the ball in the annular channel does not exceed one Hertz. For example, at a ball rotation frequency of 1 Hz, the comparator (or an operational amplifier functioning as a comparator of input common-mode voltages) will be in a linear operating mode for a long time, which indicates, firstly, the non-pulse form of the output voltage of the flowmeter, and secondly, the sensitivity of the electronic parts of the flow meter to electrical and electromagnetic interference, since there are high-resistance liquid resistances in the input circuits of the comparator. In actual operating conditions of ball flowmeters, the main source of electrical and electromagnetic interference is the power supply network 220 (380) V, 50 Hz, the output voltage will be a continuous flow of quasi-pulse voltage with a frequency of 50 Hz. The choice of a comparator (or operational amplifier) with a very high voltage gain in order to reduce the duration of the output voltage edges leads to even greater noise susceptibility of the flowmeter electronics.

The objective of the invention is to expand the areas of use of ball flow meters for electrically conductive liquids.

EFFECT: extremely wide dynamic measurement range, ensuring the operability of the flow meter at very low liquid flow rates with guaranteed suppression of the influence of electrical and electromagnetic interference, high squareness of the pulsed output voltage, reducing the likelihood of electrochemical processes in the flow meter, two functionally identical circuit outputs with a very low output resistance , the possibility of using a differential output signal, extremely low voltages between the electrodes.

The task and the technical result are achieved in a ball flow meter of an electrically conductive liquid, consisting of a cylindrical body, a helical flow guide apparatus, a ball with zero buoyancy in a liquid, made of a dielectric material, four electrodes, the electronic circuit of which, unlike the prototype, contains two operational amplifiers, on which two inverting algebraic voltage adders are implemented, the inputs of which are connected to a reference voltage source and the output of an adjacent adder.

The essence of the invention is illustrated by drawings: Fig. 1 shows the electronic circuit of the flow meter, Fig. 2 shows the design of the hydromechanical part of a ball flow meter for an electrically conductive liquid.

и

, четырех постоянных сопротивлений

,

,

и

, сопротивлений электропроводной жидкости

и

между электродами соответственно

,

и

,

, возникающими при эксплуатации расходомера, источника опорного напряжения

. Электропитание схемы обеспечивается двумя источниками напряжения постоянного тока

.The SHREZH electronic circuit consists of operational amplifiers (hereinafter - OU)

and

, four constant resistances

,

,

and

, resistance of conductive liquid

and

between the electrodes respectively

,

and

,

arising during the operation of the flowmeter, reference voltage source

. The circuit is powered by two DC voltage sources.

.

,

,

и

расположены заподлицо с внутренней поверхностью кольцевого канала, расположенного между корпусом расходомера 1 и ступицей 3. Винтообразный струенаправляющий аппарат 2 преобразует линейный поток жидкости во вращающийся поток, который приводит во вращение шар 4, имеющий нулевую плавучесть в жидкости и изготовленный из диэлектрического материала.Electrodes (Fig. 2)

,

,

and

located flush with the inner surface of the annular channel located between the body of the flowmeter 1 and the hub 3. The helical jet guide 2 converts the linear fluid flow into a rotating flow, which drives the ball 4, which has zero buoyancy in the liquid and is made of a dielectric material.

и

с частотой, пропорциональной расходу жидкости, с такой же частотой изменяет сопротивления жидкости

или

. Если шар 4 в данный момент времени находится между электродами

или

, то электрическое сопротивление жидкости

или

становится больше: соответственно

или

, где

- безразмерный коэффициент относительного изменения сопротивления жидкости,

- электрическое сопротивление жидкости между электродами

и

, когда между ними нет неэлектропроводного шара.Ball 4 moving between electrodes

and

with a frequency proportional to the flow rate of the liquid, with the same frequency changes the resistance of the liquid

or

. If ball 4 is currently between the electrodes

or

, then the electrical resistance of the liquid

or

gets bigger: accordingly

or

, where

- dimensionless coefficient of relative change in fluid resistance,

- electrical resistance of the liquid between the electrodes

and

when there is no non-conductive ball between them.

и

с коэффициентом модуляции

и частотой, пропорциональной величине расхода жидкости. Когда

, то

, если

, то

.Thus, ball 4 rotating in the annular channel SHREZH modulates the resistance

and

with modulation factor

and a frequency proportional to the fluid flow rate. When

, then

, if

, then

.

и

реализованы два алгебраических инвертирующих сумматора напряжений с резисторами отрицательных обратных связей соответственно

и

. Сумматор на ОУ

выполняет суммирование опорного напряжения

и выходного напряжения ОУ

, сумматор на ОУ

осуществляет суммирование также опорного напряжения

и выходного напряжения

, в результате чего в схеме действует положительная обратная связь.From the diagram in Fig. 1 shows that on the OS

and

implemented two algebraic inverting voltage adders with negative feedback resistors, respectively

and

. Op-amp adder

performs the summation of the reference voltage

and output voltage of the op-amp

, adder on the OU

also sums the reference voltage

and output voltage

, resulting in positive feedback in the circuit.

и

ОУ

и

, ограничиваемую параметром выбранного типа ОУ - скоростью нарастания выходного напряжения [В/сек].Positive feedback provides a very high rate of change in output voltages

and

OU

and

, limited by the parameter of the selected type of op-amp - the slew rate of the output voltage [V / s].

и

, то есть пренебречь такими их параметрами, как входной ток, разность входных токов, приведенное к входу напряжение смещения, их дрейф по температуре и некоторыми эксплуатационными ограничениями (максимально допустимые входные дифференциальное и синфазное напряжения, максимально допустимый выходной ток, скорость изменения выходного напряжения).When analyzing the process of generating the output voltage of the SHREZH in order to obtain convenient and visual mathematical functions and relationships, it is necessary to idealize the op-amp

and

, that is, to neglect such parameters as the input current, the difference in input currents, the bias voltage reduced to the input, their temperature drift and some operational limitations (maximum permissible input differential and common mode voltages, maximum permissible output current, rate of change of output voltage).

The output voltages of inverting algebraic adders, mutually connected in series, are determined by the relations:

и

. Тогда, рассматривая соотношения (1) и (2) как систему двух линейных уравнений с неизвестными

и

можно вычислить выходные напряжения ОУ

и

:When implementing the circuit in Fig. 1 it is necessary to accept the equalities of the resistances of the resistors:

and

. Then, considering relations (1) and (2) as a system of two linear equations with unknowns

and

you can calculate the output voltage of the op-amp

and

:

между электродами

и

, если шар находится за пределами зоны этих электродов, коэффициенте относительного измерения сопротивления жидкости

, если шар в данный момент времени располагается между электродами

и

, функции преобразования (3) и (4) примут вид:With known fluid resistance

between electrodes

and

, if the ball is outside the zone of these electrodes, the coefficient of the relative measurement of the resistance of the liquid

, if the ball is currently located between the electrodes

and

, transformation functions (3) and (4) will take the form:

;when the ball is between the electrodes

;

.if the ball is between the electrodes

.

,

,

и

и

,

, выходные напряжения

и

ОУ

и

в соответствии с (3) и (4) одинаковы:In the initial state of SHREZh, when the ball is at the maximum distance from the electrode zone at a given time

,

,

and

and

,

, output voltages

and

OU

and

in accordance with (3) and (4) are the same:

From formulas (3), (4), (5) and (6) two very important conclusions follow:

и

не должны быть одинаковыми (

), так как при их равенстве ОУ

и

окажутся в неактивном режиме работы (за пределами линейной зоны своей статической характеристики

, где

- коэффициент усиления по напряжению входного дифференциального напряжения

) и схема на Фиг. 1 не будет реагировать на изменения сопротивлений жидкости

и

при вращении шара в кольцевом канале, на выходах ОУ

и

установятся максимально возможные напряжения

и

или

и

, зависящие от типа интегрального ОУ и величины напряжений электропитания

и

.First, the resistances of the resistors

and

should not be the same

), since when they are equal, the OC

and

will find themselves in an inactive mode of operation (outside the linear zone of their static characteristic

, where

- voltage gain of the input differential voltage

) and the diagram in Fig. 1 will not respond to changes in fluid resistance

and

during rotation of the ball in the annular channel, at the outputs of the OS

and

maximum possible voltages are set

and

or

and

, depending on the type of integrated op amp and the magnitude of the power supply voltages

and

.

и

в электрические напряжения

и

следует, что они по величине и полярности сильно зависят от величины и соотношения сопротивлений

и

и опорного напряжения

.Secondly, from the functions of transformation of liquid resistances

and

into electrical voltages

and

it follows that in magnitude and polarity they strongly depend on the magnitude and ratio of the resistances

and

and reference voltage

.

или

. В схеме на Фиг. 1 выходным напряжением ШРЭЖ принято выходное напряжение

ОУ

SHREZH output voltage can accept voltage

or

. In the diagram in Fig. 1 output voltage SHREZH adopted the output voltage

OU

ОУ

характеризуется выражениями (6) и (7), но сдвинуто по фазе относительно выходного напряжения

ОУ

на угол, который определяется угловым расстоянием между электродами

или

.Output voltage

OU

characterized by expressions (6) and (7), but phase-shifted relative to the output voltage

OU

by an angle, which is determined by the angular distance between the electrodes

or

.

и

при известных сопротивлении жидкости

, коэффициенте относительного изменения этого сопротивления

и неограниченных по величине напряжений питания

и

. Пусть

,

, выбираем

и

из стандартных рядов E48 и E24 соответственно. Амплитудная величина выходного напряжения ШРЭЖ согласно формуле (5)

. Выходное напряжение, когда шар находится на максимальном удалении от зоны электродов,

. Если опорное напряжение

, то

и

. Если требуется однополярное, положительное выходное импульсное напряжение

, то последовательно с выходом ОУ

необходимо включить в прямом направлении импульсный или маломощный выпрямительный диод. Для ограничения амплитуды выходного напряжения ШРЭЖ достаточно установить напряжения питания схемы

и

величиной

, где

- падение напряжения на прямосмещенном диоде (примерно 0.5 В).Consider an example of calculating the expected mode of operation of the SHREZH and choosing the resistance of resistors

and

with known fluid resistance

, coefficient of relative change of this resistance

and unlimited supply voltages

and

. Let

,

, choose

and

from the standard series E48 and E24 respectively. The amplitude value of the output voltage SHREZH according to the formula (5)

. The output voltage when the ball is at the maximum distance from the electrode zone,

. If the reference voltage

, then

and

. If a unipolar, positive output pulse voltage is required

, then in series with the output of the op-amp

it is necessary to turn on in the forward direction a pulse or low-power rectifier diode. To limit the amplitude of the output voltage of the SHREZH, it is enough to set the supply voltage of the circuit

and

magnitude

, where

- voltage drop across the forward biased diode (approximately 0.5 V).

и

(пунктирная линия) и при напряжении питания

и с последовательно включённым диодом, иллюстрирующие выше рассмотренный пример расчета.On FIG. 3 shows the timing diagram of the output voltage of the SHREZh without limitation on the magnitude of the supply voltages

and

(dotted line) and at supply voltage

and with a diode connected in series, illustrating the above calculation example.

и

, при известных сопротивлении жидкости

и коэффициенте его относительного изменения

, установить амплитуду

согласно формуле (5) значительно большую, чем напряжение электропитания

. Это обеспечивает высокую (требуемую по техническим условиям на ШРЭЖ) прямоугольность выходного импульсного напряжения и его независимость от электропроводности жидкости (сопротивления

) и коэффициента

.In the process of preparing SREZH for mass production, it is recommended by the resistances

and

, with known fluid resistance

and the coefficient of its relative change

, set amplitude

according to formula (5) significantly higher than the power supply voltage

. This provides a high (required by the technical specifications for SHREZh) squareness of the output pulse voltage and its independence from the electrical conductivity of the liquid (resistance

) and coefficient

.

и

всегда практически равны нулю, так как интегральные ОУ

и

имеют очень большой коэффициент усиления по напряжению, включены в инвертирующие схемы с отрицательными обратными связями, их неинвертирующие входы присоединены к общей шине электропитания (

,

). Напряжения на электродах

и

присоединены к источнику опорного напряжения

, не превышающему, как было показано в выше рассмотренном примере, сотые доли Вольта. В прототипе на электродах, присоединенных ко входам компаратора, для оптимального режима работы схемы требуются напряжения на уровне половины напряжения электропитания схемы.Moreover, a significant technical achievement of the invention is the low electric voltages on the SREZH electrodes that do not change during the rotation of the ball in the annular channel. Electrode voltages

and

are always practically equal to zero, since the integrated op amps

and

have a very high voltage gain, are included in inverting circuits with negative feedback, their non-inverting inputs are connected to a common power bus (

,

). Electrode voltages

and

connected to a reference voltage source

, not exceeding, as shown in the above example, hundredths of a Volt. In the prototype, on the electrodes connected to the inputs of the comparator, for the optimal operation of the circuit, voltages are required at the level of half the voltage of the power supply to the circuit.

Very low and constant voltages on the electrodes of the proposed SREZH indicate a low probability of occurrence of undesirable electrochemical reactions on the electrodes.

и

:

. Вычитая (6) из (5), получим формулу:If in the automatic control system of any technological process a differential output voltage is required, then it can be the difference in the output voltages of the op-amp

and

:

. Subtracting (6) from (5), we obtain the formula:

,

,

,

, как в выше рассмотренном примере, то

. Желаемая величина и полярность выходного дифференциального напряжения устанавливается опорным напряжением

.If we take the same values

,

,

,

, as in the above example, then

. The desired value and polarity of the output differential voltage is set by the reference voltage

.

So, in the claimed spherical flow meter of a conductive liquid, high protection against the effects of electrical and electromagnetic interference is achieved, primarily at extremely low liquid flow rates, high steepness of the fronts of the output pulse voltage and very low output resistance, reducing the likelihood of electrochemical processes occurring on the electrodes of the flow meter, in general, an increase in the dynamic range, a decrease in the error in converting the liquid flow rate to the output pulse voltage, as well as an increase in the operational life of the device, which is realized by including two operational amplifiers in the electrical circuit, on which two inverting algebraic adders are implemented that add the reference voltage to the output voltage of an adjacent adder .

Claims (1)

A ball flow meter of an electrically conductive liquid, consisting of a cylindrical body, a helical flow guide apparatus, an annular channel and a ball with zero buoyancy in a liquid, made of a dielectric material, four electrodes, characterized in that its electronic circuit contains two operational amplifiers, on which two inverting algebraic voltage adder, the inputs of which are connected to a reference voltage source and the output of an adjacent adder.

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