RU2018089C1 - Multichannel ultrasonic flowmeter - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: flowmeter has two reversible piezoelectric transducers, measurement direction switch, frequency divider, pulse generator, amplifier 5, delay line, pulse shaper, quarts generator, coder, subtractor, constant-ratio frequency divider, locking pulse shaper, strobe pulse pulse shaper, two number registers, two variable-ratio dividers, reversible counter, current flowrate register and integral flowrate counter. EFFECT: enhanced accuracy. 1 dwg

Description

 The invention relates to ultrasonic measuring equipment and can be used to measure the flow of liquids in the petrochemical, oil refining and other industries.

 Known single-channel ultrasonic flow meter containing an acoustic channel, a switch and an amplifier-driver, forming a sync ring when emitting ultrasonic pulses on and against the flow of a controlled fluid, a frequency multiplier, a reversible counter, a register, a divider with a variable division factor and a liquid quantity counter, connected in series the input of the multiplier is connected to the output of the amplifier-former. A separate output of the multiplier is connected to the input of the trigger, the output of which is connected to the control inputs of the register, divider and generator of the measuring gates. The outputs of the strobe generator are connected to the control inputs of the switch and the reverse counter, the input of the read-write register and the input of the binary counter, the outputs of which are connected to the installation inputs of the divider [1].

 The known device, providing improved measurement accuracy by determining the amount of decrease in the duration of the interrupted measurement cycle relative to a given measurement cycle duration due to autocirculation failure and decrease in proportion to the value of the flow value in the previous measurement cycle, still has a measurement error due to the increase in the repetition period of the autocirculation pulses by time delay pulses in the electrical circuits of the synchro-rings.

 Closest to the proposed one is a single-channel ultrasonic flow meter containing an ultrasonic transducer with two piezoelectric elements connected via a radiation direction switch with a pulse generator and an amplifier, a frequency divider connected to a radiation direction switch, a crystal oscillator, a subtractor and an output device, a delay line, an encoder and a comparative device, the delay line being connected between the output of the amplifier and the input of the pulse generator, the second output to torogo connected to the input of the frequency divider, the encoder inputs connected to the outputs of the quartz oscillator and frequency divider, respectively, and its output through a subtracter and a comparator device connected to the output device [2].

 The known device, providing improved measurement accuracy due to the formation of numbers that display the total periods of packs of autocirculation pulses along and against the flow, and subtracting from them a constant number that displays the delay time of autocirculation pulses in electrical circuits, has an error in measuring the integral flow rate when autocirculation is interrupted.

 The purpose of the invention is to improve the accuracy of measurement.

 This goal is achieved by the fact that in a device containing an ultrasonic transducer with two piezoelectric elements connected via a radiation direction switch with a pulse generator and an amplifier, an autocirculation frequency divider connected to the control input of the radiation direction switch, a crystal oscillator, a subtractor, a delay line connected to amplifier, an encoding device, the inputs of which are connected to the outputs of a crystal oscillator and an autocirculation frequency divider, and its output is connected inen with the input of the subtracting device, a shaper of reset-start pulses, a frequency divider with a constant division ratio and a shaper of blocking pulses, the output of which is connected to the control input of the subtracting device, the first number register, the first divider with a variable division coefficient, and a reversible counter are introduced in series , the register of the current flow rate and the counter of the integral flow rate, connected in series to the second register of the number and the second divider with variable k a division factor, the output of which is connected to the second input of the reverse counter, as well as a strobe generator, the output of which is connected to the control input of the reverse counter, and the reset-start pulse shaper is connected between the output of the delay line and the input of the pulse generator, the output of the crystal oscillator is additionally connected to the inputs of the divider frequencies with a constant division factor and the first and second frequency dividers with a variable division coefficient, the inputs of the first and second number registers are connected to the outputs of the subtractor, and the input of the blocking pulse generator is connected to the input of the pulse generator.

 The drawing shows a block diagram of the proposed flow meter.

 The flowmeter contains a converter 1 with two piezoelectric elements 2 and 3, a pulse generator 4, an amplifier 5, a radiation direction switch 6, a line 7, an autocirculation frequency divider 8, an encoding device 9, a crystal oscillator 10, a subtractor 11, a crystal oscillator frequency divider 12 with a constant dividing coefficient, shaper 13 pulses of reset-start, shaper 14 pulses of blocking, register 15 of the number "upstream", register 16 of the number "upstream", two frequency dividers 17 and 18 of the crystal oscillator with variable coefficients ntami dividing down counter 19, generator 20 strobes, the register 21 of the current flow, integrated flow meter 22.

+ t₃ (1)
и при излучении против потока
T_-v=

+ t₃ (2) где v - средняя скорость потока среды;
С - скорость звука в неподвижной среде;
L - расстояние между пьезоэлементами;
α - угол между направлением ультразвукового луча и осью трубопровода;
t_з - время задержки сигналов в линии задержки.In an electrical circuit consisting of a transducer 1 with piezoelectric elements 2 and 3, a generator 4, an amplifier 5, a switch, a line 7, a former 13, a pulse sequence arises which, when emitted by the fluid flow, is determined by the period
T _{+ v} =

+ t ₃ (1)
and when radiation against the stream
T _-v =

+ t ₃ (2) where v is the average flow rate of the medium;
C is the speed of sound in a stationary medium;
L is the distance between the piezoelectric elements;
α is the angle between the direction of the ultrasound beam and the axis of the pipeline;
t _s - the delay time of the signals in the delay line.

 The direction of radiation changes with a frequency that is set by the generator 4 through a divider 8 with a division ratio N.

The pulses from the generator 10 are fed to an encoding device 9, in which, using these pulses, the switching cycle durations are converted into numbers equal to NfT _{+ v} for radiation downstream and NfT _-v for radiation upstream.

 The frequency f of the crystal oscillator is selected depending on the resolution requirements of the flowmeter.

At the moment of operation of the switch 6, the number from the output of the encoder 9 is fed to a subtractor, where a constant number equal to Nft _s is subtracted from it.

 Thus, in two clock cycles of the switch 6, two numbers are formed in the subtractor 11.

=

(T_+v-t₃) (5)
и

= $\genfrac{}{}{0ex}{}{\text{N}}{\text{R}}$ _(T_-v-t₃) (6)
соответственно, которые поступают на два входа реверсивного счетчика 19 соответственно. Реверсивный счетчик 19 по сигналу длительностью Т_стр формирователя 20 стробов производит сначала суммирование импульсов с периодом

(T_+v-t₃) , а затем вычитание импульсов с периодом

(T_-v-t₃) . Пропорциональное расходу разностное число импульсов.W = Nf (T _{+ v} - t _s ) (3) and
Z = Nf (T _-v - t _s ) (4)
The numbers W / R and Z / R, where R is a constant number that is several times greater than the number N, are recorded in registers 15 and 16, respectively, which are received at the installation inputs of the dividers 17 and 18, respectively. At the outputs of the dividers 17 and 18 there are sequences of pulses with periods

=

(T _{+ v} -t ₃ ) (5)
and

= $\genfrac{}{}{0ex}{}{\text{N}}{\text{R}}$ _ (T _-v -t ₃ ) (6)
respectively, which are fed to two inputs of the reverse counter 19, respectively. The reversible counter 19, according to a signal of duration T _page of the gate generator 20, first performs the summation of pulses with a period

(T _{+ v} -t ₃ ) and then subtracting pulses with a period

(T _-v -t ₃ ). The differential number of pulses proportional to the flow rate.

-

=

· V
(7) записывается в регистр 21. Информацию об интегральном расходе накапливают в счетчике 22 путем передачи на его вход пачки импульсов с регистра 21 в конце каждого цикла работы реверсивного счетчика 19.

-

=

V
(7) is recorded in register 21. Information about the integral flow rate is accumulated in the counter 22 by transmitting to its input a packet of pulses from the register 21 at the end of each operation cycle of the reverse counter 19.

The division coefficient M of the divider 12 is chosen such that M> T _-v max.

 With the stability of autocirculation, the reset-start pulses of the shaper 13 are fed to the control input of the divider 12, as a result of which there are no pulses with a frequency f / M at the output of the divider 12. When the autocirculation is disrupted due to a gas bubble or interference at the output of the divider 12, a pulse arises which is fed to the input of the generator 4 and the autocirculation is restored. In this case, the control input of the subtracting device 11 receives a blocking pulse of the shaper 14, which blocks the arrival of a number from the encoder 9, and the numbers recorded before the autocirculation breakdown are stored in the registers 15 and 16.

 Thus, a short breakdown of autocirculation does not lead to loss of flow information.

Claims (1)

 A SINGLE-CHANNEL ULTRASONIC FLOW METER containing an ultrasonic transducer with two piezoelectric elements connected via a radiation direction switch to a pulse generator and an amplifier, an output connected to a delay line, and an autocirculation frequency divider whose input is connected to the output of the pulse generator and the output to the control input of the radiation direction switch and the first input of the encoder, the second input of which is connected to the output of the crystal oscillator, and the output to the input of the subtractor TWA, characterized in that it is connected in series with a shaper of pulses of reset-start, a frequency divider with a constant division coefficient and a shaper of blocking pulses, the output of which is connected to the control input of the subtractor, the first register of the number is connected in series, the first divider with a variable division coefficient, a reversible counter, a register of the current value of the flow rate and a counter of the integral value of the flow, connected in series to the second register of the number and the second divider variable dividing coefficient, the output of which is connected to the second input of the reverse counter, as well as a strobe generator, the output of which is connected to the control input of the reverse counter, and the reset-start pulse shaper is connected between the output of the delay line and the input of the pulse generator, the output of the crystal oscillator is additionally connected to the inputs frequency divider with a constant division coefficient and the first and second frequency dividers with a variable division coefficient, the inputs of the first and second registers L connected to the outputs of the subtractor and the input of the locking pulse coupled to the input of the pulse generator.

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