SU1267166A1

SU1267166A1 - Method for calibration of liquid flowmeters with analogue electric output signal

Info

Publication number: SU1267166A1
Application number: SU843772501A
Authority: SU
Inventors: Михаил Наумович Левин; Виктор Павлович Ефимов; Геннадий Николаевич Миронов; Александр Михайлович Пергамент; Дмитрий Павлович Прунов; Николай Николаевич Тимошенко
Original assignee: Предприятие П/Я В-2572
Priority date: 1984-07-13
Filing date: 1984-07-13
Publication date: 1986-10-30

Description

Изобретение относится к измерительной технике, а именно к измерению расходов жидкости, и может быть использовано для градуировки жидкостных расходомеров с аналоговыми электрическим выходным сигналом, например для электромагнитных индукционных расходомеров, в широком интервале значений расхода и температур жидкости.The invention relates to measuring technique, namely to measuring liquid flow rates, and can be used for graduation of liquid flow meters with an analog electrical output signal, for example for electromagnetic induction flow meters, in a wide range of flow rates and liquid temperatures.

Целью изобретения является уменьшение погрешности задания расхода и увеличения производительности процесса градуировки.The aim of the invention is to reduce the error of the task flow and increase the performance of the calibration process.

На фиг. I представлена блок-схема устройства для осуществления предлагаемого способа градуировки жидкостных расходомеров с аналоговым электрическим выходным сигналом; на фиг.2 и 3 - временные диаграммы работы иммерсионного измерителя массы с подключенным, к нему измерителем периода и работы аналого-цифрового преобразователя.In FIG. I presents a block diagram of a device for implementing the proposed method for calibrating liquid flow meters with an analog electrical output signal; Figures 2 and 3 are timing diagrams of the operation of an immersion mass meter with a period meter and an analog-to-digital converter connected to it.

Устройство для осуществления способа содержит (фиг. 1) мерный резервуар 1 с измерителем 2 количества жидкости 3 в резервуаре, выполненном в виде иммерсионного’измерителя массы жидкости с частотно-модулированным выходным сигналом, получаемым от струнного датчика 4, преобразующего момент выталкивающей силы, действующей на погружаемый элемент 5, в частоту колебаний механического резонатора, технологический трубопровод 6, соединенный с мерным резервуаром 1 и используемый для размещения проверяемого расходомера 7, сливной резервуар 8, насос 9 с трубопроводами 10 и 11, первый из которых - напорный и соединен с другим концом технологического трубопровода 6, а второй всасывающий и соединен со сливным резервуаром, электронный блок 12 формирования команд, выполненный в виде формирователя прямоугольных импульсов по переднему фронту частотномодулированного сигнала с датчика 4, клапан 13 с трубопроводом 14, соединенный с мерным резервуаром I, источник 15 давления сжатого газа, выполненный в виде емкости, соединенный с трубопроводом 14 клапана 13, измеритель 16 периода следования импульсов, вход которого соединен с выходом блока 12, аналого-цифровой преобразователь 17, управляющий вход которого также соединен с выходом блока 12, а измерительный - с выходом расходомера 7, и цифровой регистратор 18, входы которого соединены 5 с выходами измерителя 16 периода и аналого-цифрового преобразователяThe device for implementing the method comprises (Fig. 1) a measuring tank 1 with a liquid quantity meter 3 in the tank, made in the form of an immersion liquid mass meter with a frequency-modulated output signal received from a string sensor 4, which converts the moment of the buoyant force acting on immersed element 5, in the frequency of oscillations of the mechanical resonator, the process pipe 6 connected to the measuring tank 1 and used to accommodate the tested flowmeter 7, drain tank 8, pump 9 s pipelines 10 and 11, the first of which is pressure head and connected to the other end of the process pipe 6, and the second suction and connected to the drain tank, an electronic command generation unit 12, made in the form of a square-wave pulse generator along the leading edge of the frequency-modulated signal from sensor 4, the valve 13 with a pipe 14 connected to the measuring tank I, a source of compressed gas pressure 15, made in the form of a container, connected to the pipe 14 of the valve 13, a meter 16 of the pulse repetition period, the input otorrhea connected to the output unit 12, an analog-digital converter 17, a control input of which is also connected to the output unit 12 and the measuring - in a yield meter 7, and the digital recorder 18, whose inputs are connected 5 to the outputs of the meter 16 period and the analog-to-digital converter

17. Кроме того, для удобства заполнения системы жидкостью и ускорения возврата ее в исходное положение 10 устройство снабжено вентилями 19 и 20, установленными на мерном резервуаре 1 и сливном резервуаре 8, а также вентилем 21 с трубопроводом 22, соединенными с источником 15 давления сжатого газа и сливным резервуаром 8.17. In addition, for the convenience of filling the system with liquid and accelerating its return to the initial position 10, the device is equipped with valves 19 and 20 installed on the measuring tank 1 and drain tank 8, as well as valve 21 with a pipe 22 connected to a source of compressed gas pressure 15 and drain tank 8.

Способ осуществляют следующим образом. .The method is as follows. .

Устройство, с помощью которого осуществляют способ, подготавливают к работе, для чего жидкость 3 насосом 9 закачивают в мерный резервуар 1 из сливного резервуара 8. Клапан 13 при этом закрыт, а в источнике ²⁵ 15 имеется давление сжатого газа, достаточное для создания максимальной скорости потока жидкости в трубопроводе 6. Уровень жидкости 3 в мерном резервуаре I контролируется 30 по показаниям измерителя 16 периода.The device with which the method is carried out is prepared for operation, for which purpose the liquid 3 is pumped into the measuring tank 1 from the drain tank 8. The valve 13 is closed, and the source ²⁵ has a pressure of compressed gas sufficient to create a maximum flow rate liquid in the pipeline 6. The liquid level 3 in the measuring tank I is controlled 30 according to the readings of the meter 16 period.

В момент пуска установки в действие насос 9 выключается, клапан 13 открывается и над жидкостью 3 в ре-, зервуаре 1 создается давление, близкое к исходному давлению в источнике 15. Это давление вынуждает жидкость 1 течь по трубопроводу 6 и далее через трубопроводы 10 и 11 и ₄₀ выключенный насос 9 в сливной резервуар. Таким образом, формируют и пропускают через проверяемый расходомер и образцовый измеритель количества жидкости в резервуаре поток жидкости с монотонно убывающим расходом. На выходе расходомера 7 при этом появляется аналоговый электрический выходной сигнал, а на выходе иммерсионного измерителя 2 - частотно-моду₅₀ лированный сигнал с периодом, изменяющимся по зависимости кривой 23, приведенной на фиг. 2. Показания образцового измерителя и расходомера можно регистрировать в цифровой фор55 ^Ме’At the moment of starting up the installation, the pump 9 turns off, the valve 13 opens and a pressure is created above the liquid 3 in the reservoir 1 close to the initial pressure in the source 15. This pressure forces the liquid 1 to flow through pipeline 6 and then through pipelines 10 and 11 and ₄₀ turned off pump 9 to the drain tank. Thus, a fluid flow with a monotonously decreasing flow rate is formed and passed through a tested flow meter and an exemplary liquid quantity meter in the tank. An analog electrical output signal appears at the output of the flowmeter 7, and a frequency-modulated signal ₅₀ with a period varying according to curve 23 of FIG. 2. The readings of the reference meter and flow meter can be recorded in digital form55 ^Me '

Объемы мерного резервуара 1 и источника 15 давления сжатого газа подобраны так, что их отношение равно отношению максимального расхода жидкости к минимальному, например 10:1. При этом давление газа по мере истечения жидкости 3 падает, скорость истечения жидкости, а, следовательно, 5 и расход монотонно убывают.The volumes of the volumetric reservoir 1 and the source 15 of the pressure of the compressed gas are selected so that their ratio is equal to the ratio of the maximum liquid flow to the minimum, for example 10: 1. In this case, the gas pressure as the fluid 3 expires, the fluid flow rate, and, therefore, 5 and the flow rate decrease monotonically.

Одновременно убывает текущее значение периода Т частотно-модулированного сигнала. Поскольку измеритель 16 периода регистрирует среднее значение 10 периода за интервал измерения, то цифровой код Nj на его выходе изменяется в соответствии с кривой 24 на фиг. 2. Этот код появляется только после окончания интервала измерения, 15 т.е. запаздывает относительно момента, в который текущее значение периода совпадает с полученным средним значением, на половину интервала измерения (принимая пренебрежимо малой погрешностг, такого приближенного представления, связанную нелинейностью зависимости кривой 23 на малом интервале). Для получения не абсолютного значения массы жидкости 3 в ре- 25 зервуаре 1, а ее изменения за время одного измерения необходимо вычесть два соседних результата измерения массы. Так как каждое из них относится к середине интервала измерения,30 то среднее значение производной, вычисляемой по конечным разностям, относится к середине отрезка между .этими точками, т.е. к точке, являющейся границей двух соседних интервалов времени измерения.At the same time, the current value of the period T of the frequency-modulated signal decreases. Since the period meter 16 registers the average value of 10 of the period for the measurement interval, the digital code Nj at its output changes in accordance with curve 24 in FIG. 2. This code appears only after the end of the measurement interval, 15 ie lags relative to the moment at which the current value of the period coincides with the obtained average value by half the measurement interval (assuming a negligible error, such an approximate representation, related by the nonlinearity of the dependence of curve 23 on a small interval). To obtain not the absolute value of the mass of liquid 3 in the tank 1, but its changes during one measurement, it is necessary to subtract two adjacent mass measurement results. Since each of them refers to the middle of the measurement interval, 30, the average value of the derivative calculated from the finite differences refers to the middle of the segment between these points, i.e. to a point that is the boundary of two adjacent measurement time intervals.

В то же время сигнал проверяемого расходомера (кривая 25 на фиг. 3) отслеживает значение мгновенного расхода практически без задержки. По- ⁴⁰этому измерения необходимо производить в тех же точках, для которых вычисляется производная сигнала иммерсионного измерителя массы, т.е. в точках на границах интервалов из- ⁴⁵мерения. Последнее достигается тем, что по переднему фронту частотномодулированного сигнала формируют прямоугольные импульсы и одновременно с того же датчика измеряют 'интер- 50 валы времени между ними. Средний массовый расход в i-ый момент времени определяется как взятое для i-ro и (i+l)-ro моментов времени отношение· разности абсолютных значений масс ‘55 жидкости к полусумме- этих же интервалов. Сигнал с поверяемого расходомера измеряют в момент прохождения прямоугольных импульсов на управляющий вход аналого-цифрового преобразователя, т.е. в ΐ-ый момент времени, тем самым производят синхронизацию сигналов частотного датчика и расходомера по передним фронтам сш налов частотного датчика.At the same time, the signal of the flowmeter under test (curve 25 in Fig. 3) monitors the value of the instantaneous flow rate practically without delay. ⁴⁰ Po- this measurement must be made at the same points for which the derivative is calculated immersion mass meter signal, i.e. at points on the interval boundaries due ⁴⁵ dimensional. The latter is achieved by the fact that rectangular pulses are formed on the leading edge of the frequency-modulated signal, and at the same time, time intervals between them are measured from the same sensor. The average mass flow rate at the i-th moment of time is defined as the ratio of · the difference in the absolute values of the masses of '55 liquids to half-sum of the same intervals taken for i-ro and (i + l) -ro instants of time. The signal from the calibrated flow meter is measured at the instant of passage of the rectangular pulses to the control input of the analog-to-digital converter, i.e. at the ΐ-th moment of time, thereby synchronizing the signals of the frequency sensor and the flow meter along the leading edges of the signals of the frequency sensor.

После получения значений массовых расходов по мерному баку и расходомеру в синхронизированные моменты времени определяют градуированную характеристику расходомера.After receiving the mass flow values for the measuring tank and the flow meter at synchronized time points, the graduated characteristic of the flow meter is determined.

Таким образом, путем одновременного непрерывного измерения массы и интервалов времени одним датчиком с частотным выходным сигналом достигается уменьшение погрешности задания расхода в сравниваемые с показателями градуируемого расходомера моменты 20 времени.Thus, by simultaneous continuous measurement of mass and time intervals by one sensor with a frequency output signal, a reduction in the error in the task of the flow is achieved at time moments 20 compared with the indicators of the calibrated flowmeter.

Claims

The invention relates to a measurement technique, namely, to measuring flow rates of a liquid, and can be used to calibrate liquid flow meters with analog electrical output, for example, electromagnetic induction flow meters, over a wide range of flow rates and liquid temperatures. The aim of the invention is to reduce the error in setting the flow rate and increase the productivity of the calibration process. FIG. 1 shows a block diagram of an apparatus for carrying out the proposed method for calibrating liquid flow meters with an analog electrical output signal; FIGS. 2 and 3 are time diagrams of the operation of an immersion mass meter with a period meter and an analog-digital converter operation connected to it. A device for carrying out the method contains (FIG. 1) a measuring vessel 1 with a measuring instrument 2 of a quantity of liquid 3 in a reservoir made in the form of an immersion measuring device for the mass of a liquid with frequency-modulated output signal received from a string sensor 4 that converts the moment of pushing force acting on the submersible element 5, to the frequency of oscillations of the mechanical resonator, process piping 6, connected to the measuring tank 1 and used to accommodate the flow meter to be tested 7, drain tank 8, pump 9 with pipes 10 and 11, the first of which is pressure and is connected to the other end of the process pipe 6, and the second is suction and is connected to a drain tank, an electronic unit 12 forming commands, filled in the form of a rectangular pulse former on the leading edge of the frequency-modulated signal from sensor 4, valve 13 with pipeline 14., connected to measuring tank I, source 15 of pressure of compressed gas, made in the form of a container, connected to pipe 14 of valve 13, meter 16 of the pulse period, the input of which is connected to the output of block 12, analog-to-digital converter 17, the control input 66 of which is also connected to the output of block 12, and the measuring one - to the output of flow meter 7, and a digital recorder 18, whose inputs are connected to the outputs of the period 16 meter and analog digital converter 17. In addition, for convenience of filling the system with liquid and speeding up its return to the initial position, the device is equipped with valves 19 and 20 installed on measuring tank 1 and drain tank 8, as well as valve 21 with pipe 22, connecting With a pressurized gas source 15 and a discharge tank B, the method is carried out as follows. The device with which the method is carried out is prepared for operation, for which the liquid 3 is pumped by pump 9 into the measuring tank 1 from the drain tank 8. The valve 13 is closed and the pressure of compressed gas in source 15 is sufficient to create a maximum flow rate liquids in the pipeline 6. The level of the liquid 3 in the measuring tank 1 is monitored according to the indications of the period meter 16. At the time of installation start-up, the pump 9 is turned off, the valve 13 is opened and above the liquid 3 in the re-. A pressure 1 is created in the reservoir 1, which is close to the initial pressure in source 15. This pressure forces fluid 1 to flow through pipe 6 and then through pipes 10 and 11 and pump 9 off to the drain tank. Thus, the flow of the systok with monotonously decreasing flow is formed and passed through the flow meter being tested and an exemplary measuring instrument for the amount of liquid in the reservoir. At the output of the flow meter 7, an analog electrical output signal appears, and at the output of the immersion meter 2, a frequency-modulated signal with a period varying according to the curve 23 shown in FIG. 2. The sample meter and meter readings can be recorded in digital form. The volumes of the measuring tank 1 and the source 15 of the pressure of the compressed gas are chosen so that their ratio is 3 oTHOiiGHnio of the maximum flow rate of the liquid to the minimum, for example 10: 1 At that, the gas pressure decreases as the liquid flows 3, the speed and flow of the liquid, and, therefore and consumption monotonously decrease. At the same time, the current period T of the frequency modulated signal decreases. Since the period meter records the average value of the period for the measurement interval, the digital code NJ at its output varies in accordance with curve 24 in FIG.

2. This code appears only after the end of the measurement interval, i.e. lags behind the moment at which the current period value coincides with the average value obtained by half the measurement interval (assuming a negligibly small error of such an approximate representation is due to the nonlinearity of the dependence of curve 23 on a small interval). In order to obtain not the absolute value of the mass of liquid 3 in reservoir 1, but its changes during one measurement, it is necessary to subtract two adjacent results of mass measurement. Since each of them belongs to the middle of the measurement interval, the average value of the derivative, calculated from finite differences, refers to the midpoint of the segment between these points, i.e. to the point that is the boundary of two adjacent measurement time intervals. At the same time, the signal of the flow meter being tested (curve 25 in FIG. 3) monitors the instantaneous flow rate with almost no delay. Therefore, measurements must be made at the same points for which the derivative of the signal of the immersion mass meter is calculated, i.e. at points at the boundaries of the measurement intervals. The latter is achieved by forming square pulses on the leading edge of the frequency-modulated signal, and simultaneously with the same sensor measuring the time intervals between them. The average mass flow rate at the i-th time instant is defined as the dp i-ro and (i + l) -ro time points, the ratio of the difference between the absolute values of the mass of the liquid and the half-sum of the same intervals. The signal from the calibrated flow meter is measured at the time of passage of 664 1 rectangular pulses to the control input of the analog-digital converter, i.e. The i-th instant of time, thereby synchronizing the signals of the frequency sensor and the flow meter “1 along the leading edges of cui of the frequency sensor. After obtaining the mass flow rates for the measuring tank and the flow meter at synchronized times, the graded characteristic of the flow meter is determined. Thus, by simultaneous continuous measurement of the mass and time intervals by a single sensor with a frequency output signal, a reduction in the error in setting the flow rate is achieved at times compared with the indicators of the calibrated flow meter. The method of calibration of liquid flow meters with analog electric output signal, which consists in expelling the liquid through the graduated flow meter from the measuring tank with liquid and the immersed element of the load cell placed in it, and measuring the output of the flow meter in synchronized moments time, as well as the duration of the time intervals between these moments and determine the average mass flow rate and the calibration characteristic of the skimmer at the i-th instant of time, so that, in order to reduce the error in setting the flow rate and increase the drive of the calibration process, when displacing the liquid from the measuring tank, the flow is monotonically reduced, with a frequency output signal, and the average mass flow rate at the i-th time instant is determined as taken for i-ro and (i + l) -ro times, the ratio of the difference between the absolute values of the mass of the liquid and the half-sum of these same time intervals, compare this average ma ssovogo flow with the indications of the calibrated flow meter at the i-th instant of time, and the synchronization of the signals from the frequency sensor and the flow meter is made on the leading edges of the signals of the frequency sensor.

23 2ii

FIG. 2

26

fig.Z