RU2146358C1 - Device measuring level of liquid media - Google Patents

Abstract

FIELD: petroleum refining industry, water supply systems. SUBSTANCE: proposed device includes measurement tube with acoustic reflector of sounding signal and detectors of acoustic signals, amplifier-former of sounding signals, amplifier-former of received signals, circuit measuring time interval functionally related to measured level and indicator. Second detector of acoustic signals is placed below first detector at fixed distance from it and above maximum permissible level of liquid for given reservoir. Both detectors are located below level of radiator on outer wall of measurement tube and are coupled with inputs to its space via matching transformers and with outputs to signal input of circuit measuring time interval functionally related to measured level via amplifier-former of received signals. Given circuit is based on microprocessor realizing program of control over measurement process, of computation of average value of measured level of liquid in accordance with assignment and initial data by presented formula. First output of microprocessor is connected to control input of amplifier-former of sounding video signals, its second output is linked to input of digital indicator of measured level and its third output is used for connection to outside devices. EFFECT: high precision, reliability of measurement of level of liquid in reservoirs and chutes of various types, simplified design, low power consumption, high operational characteristics and reduced effect of outside noise. 3 dwg

Description

 The invention relates to measuring the level of liquids by the acoustic method and can be widely used in automated control and metering systems in the oil and gas refining industry, water supply and sanitation in public utilities, other sectors of the economy related to the production, storage and use of liquids at normal atmospheric pressure.

 The relevance of developing new means of measuring the level of liquid in open and closed, including underground tanks and trays, is determined by the need for automated operational accounting of the presence and consumption at all stages of their production, storage and sale.

 Currently, various contact and remote devices for measuring the level of liquid media have been developed, in which various frequency ranges are used, including ultrasonic and sound (acoustic). However, the existing device for measuring the liquid level does not have sufficient versatility, reliability, accuracy, adaptability, the ability to flexible, operational software adjustment in relation to operating conditions.

Known acoustic level sensor (AS N 821939, M. class. ³ G 01 F 23/28), containing measuring and reference sensors, each of which consists of a block of excitation of probe pulses, an amplifier, emitter and receiver of acoustic signals included in auto-circulation circuit, a reference sensor pipe equipped with a fixed reflector, a measuring sensor pipe and a recording unit. In order to increase the accuracy of measurements in the reference tube, additional fixed reflectors are installed, and a synchronization unit is inserted, which is connected between the output of the amplifier of the reference acoustic sensor and the excitation block of the probe pulses of this sensor.

 The disadvantages of this device are the use of separate radiation and reception units for each individual measuring and reference tubes, the presence of several fixed reflectors in the reference tube and the use of an autocirculation circuit, which ultimately can lead to an increase in the level measurement error in some intervals of its values due to interference phenomena in the reference pipe, discrepancies in the parameters of the transceiver devices of both channels, residual errors in the autocirculation scheme.

A device for measuring the level of liquid media (see AS USSR N 1048322, M. CL ³ G 01 F 23/28), containing located above the controlled medium, a two-beam acoustic emitter, a probe pulse generator, an amplifier driver, electronic keys , waiting controlled multivibrator, reversible counter and trigger.

The disadvantages of this device, which can lead to a decrease in measurement accuracy, are the use of a two-beam acoustic emitter, which provides simultaneous emission and reception of signals in mutually perpendicular planes, the need for "accurate" installation of this emitter taking into account the requirements for creating a "reference" distance l ₀ in mutually perpendicular planes , a complex algorithm for generating information signals, the use of second-reflected signals, which imposes additional requirements anija the level of radiated power, the location of a reference distance in the horizontal plane.

A known acoustic level meter (US Pat. RU N 2010180, M.cl. ⁵ G 01 F 23/28) containing a sound pipe made in the form of a pipe, equipped with a reflector with a polished surface, an acoustic measuring element connected to the recording unit, a rod waveguide installed coaxially in the pipe. The reflector is made in a trapezoidal shape and mounted on a pipe opposite the working end of the waveguide. In this case, the side faces of the reflector are installed at an angle of 60 ^o to the horizontal side of the reflector, which is perpendicular to the working end of the waveguide.

 The disadvantages of this device are determined by the extremely complex structure of the sound duct, which limits the scope of its use, in addition, the introduction of a reflector into the sound duct can lead to interference phenomena due to multiple reflection from its surface.

The closest in purpose and technical essence to the proposed technical solution, the prototype analogue can serve as an acoustic level gauge, protected by copyright certificate of the USSR N 1615559, M. class. ⁵ G 01 F 23/28. It contains a measuring tube with an acoustic probe emitter and a receiver of acoustic signals, an amplifier-driver of a probe video pulse, an amplifier-driver of received pulses, a measurement circuit for a time interval proportional to the measured level, and an indicator.

 The main disadvantage of this device (prototype) is the achievement of the goal due to the complex algorithm for processing the received signal, which, however, does not exclude a decrease in the reliability of the measurement results due to the variability of external factors (the installation of a single temperature sensor does not provide reliable metering usually uneven in vertical and horizontal temperature distribution planes inside the tank). Other disadvantages are associated with the installation of the emitter and receiver at the same level, which can lead to an unreasonable increase in the diameter of the pipe, a decrease in the energy performance of the device and a limitation of the possibilities of its use.

 The objective of the present invention is to develop a device that improves the accuracy and reliability of measuring the level of liquids in tanks and trays of various types (open, closed, underground), simplifies the algorithm for generating information signals, reduces the influence of external noise, reduces energy consumption, improves operational parameters.

где L - расстояние от второго приемника до дна резервуара; l₀ - фиксированное расстояние между приемниками; N - количество последних отсчетов, по которым проводится усреднение результатов измерения уровня; t_xi - временной интервал между зондирующим и отраженным сигналами, принятыми вторым приемником в i - м измерении; t_oi - временной интервал между приемом зондирующего сигнала, принятого первым и вторым приемниками в i - м измерении; t'_oi - временной интервал между приемом отраженного сигнала вторым и первым приемниками в i - м измерении. При этом первый выход микропроцессора, синхронизирующий, соединен с управляющим входом усилителя - формирователя зондирующих видеосигналов, к выходу которого подключен акустический излучатель, второй выход микропроцессора, информационный, соединен с входом индикатора измеряемого уровня, а третий выход служит для связи с внешними устройствами.According to the invention, the task is solved as follows. In the device for measuring the level of liquid media containing a measuring tube with an acoustic emitter of a sounding signal and a first receiver of acoustic signals, an amplifier is a driver of a sounding video signal, an amplifier is a driver of received signals, a measurement circuit of a time interval functionally associated with the measured level, and an indicator is further introduced a second receiver of acoustic signals located below the first receiver at a fixed distance from it and above the maximum allowable level liquid for the reservoir. Moreover, both receivers are installed below the level of the emitter on the outer wall of the measuring tube and are connected by inputs to its cavity through matching transformers, and outputs through an amplifier — a shaper of received signals are connected to the signal input of the measurement circuit of the time interval functionally connected with the measured level, made in the form of a microprocessor, implementing a predetermined program and controls the measuring process of calculating the average value of the measured liquid level l _x under the original Func E by the formula

where L is the distance from the second receiver to the bottom of the tank; l ₀ - fixed distance between receivers; N is the number of recent readings by which the results of level measurement are averaged; t _xi is the time interval between the probing and reflected signals received by the second receiver in the i-th dimension; t _oi is the time interval between the reception of the probe signal received by the first and second receivers in the i-th dimension; t ' _oi is the time interval between the reception of the reflected signal by the second and first receivers in the i-th dimension. In this case, the first output of the microprocessor, synchronizing, is connected to the control input of the amplifier - the shaper of the probing video signals, to the output of which an acoustic emitter is connected, the second output of the microprocessor, information, is connected to the input of the indicator of the measured level, and the third output is used to communicate with external devices.

The task in this invention is achieved as follows:
- the introduction of a second receiver of acoustic signals, mounted below the first receiver, at a fixed distance from it, allows you to use a simple algorithm for generating information signals, provides the possibility of using part of the measuring tube located between the first and second receivers as a reference section, necessary to improve the accuracy of measurements level;
- the introduction of a microprocessor provides the expansion of the device’s functionality, the possibility of individual adaptation of each device to operating conditions, increase the commercial accuracy of measurements due to the current averaging of measurement results, connecting the device to various data collection and processing systems;
- the installation of the first and second receivers on the outer wall of the measuring tube improves the reliability of the device by eliminating interference phenomena inside the measuring tube, provides increased noise immunity of the device from internal and external interference, increases the manufacturability of the device during its manufacture and improves operational characteristics.

раз.The set of the foregoing features of the invention is implemented in the formula for measuring the level L = f (l _W ; t _xi ; t _oi ; t ' _oi ), which can significantly reduce the systematic error due to the error in the installation of receivers and the spread of the length of the reference distance, as well as to reduce random errors in

time.

The invention is illustrated by drawings, which depict:
in FIG. 1 is a block diagram of the proposed device for measuring the level of liquid media;
in FIG. 2 is a timing diagram of the operation of the device;
in FIG. 3 is an illustration of eliminating the influence of an error in the installation of receivers.

 The proposed device for measuring the liquid level in the tank (tank) 1 contains a measuring pipe 2, vertically mounted in the tank 1. In the lower part of the pipe 2 there are openings 3 for the liquid from the tank 1 to the measuring pipe 2, and in the upper part there are ventilation holes 4 the connection of its internal cavity with the atmosphere to eliminate excess vapor pressure of the liquid and achieve uniform distribution along the measuring tube 2. At the upper end of the measuring tube 2 is installed acoustic emitter 5. On the outer wall of the pipe 2 are installed at a fixed distance from each other in height two receivers 6, 7 of acoustic signals, the first, upper, receiver 6 is located below the level of the emitter 5, and the second, lower, receiver 7 is located above the maximum allowable liquid level for this reservoir 1. The inputs of the receivers 6, 7 are connected with the internal volume of the pipe 2 using matching transformers 8, 9 (communication holes). The secondary circuit of the device contains an amplifier — shaper 10 of the probing video signals, an amplifier — shaper 11 of received signals, a microprocessor 12 that implements a given program for controlling the measurement process, calculating the average value of the measured level depending on the purpose and source data, controlling the indicator 13, and communication with external devices. The outputs of both receivers 6, 7 through the amplifier - driver 11 of the received signals are connected to the signal input of the microprocessor 12, the first, synchronizing, the output of which is connected to the control input of the amplifier - driver 10 of the probing video signals, connected by its output to the acoustic emitter 5. The second output of the microprocessor 12, informational, connected to the input of the indicator 13 of the measured level. The third output of the microprocessor 12 is used for communication with external devices, such as computers, etc.

где L - расстояние от второго приемника 7 до дна резервуара 1; l₀ - фиксированное расстояние между приемниками 6, 7; N - количество отсчетов, по которым проводится усреднение результатов измерения уровня; t_xi - временной интервал между зондирующим и отраженным сигналами, принятыми вторым приемником в i - м измерении; t_oi - временной интервал между приемом зондирующего импульса первым и вторым приемниками в i - м измерении; t'_oi - временной интервал между приемом отраженного сигнала вторым и первым приемниками i - м измерении.The calculation of the measured level in the microprocessor 12 is carried out according to the formula:

where L is the distance from the second receiver 7 to the bottom of the tank 1; l ₀ - a fixed distance between the receivers 6, 7; N is the number of samples over which the level measurement results are averaged; t _xi is the time interval between the probing and reflected signals received by the second receiver in the i-th dimension; t _oi is the time interval between the reception of the probe pulse by the first and second receivers in the i-th dimension; t ' _oi is the time interval between the reception of the reflected signal by the second and first receivers of the i-th dimension.

 The proposed device for measuring the level of liquid media works as follows.

The microprocessor 12 generates a signal (see Fig. 2a) to start the amplifier - shaper 10 of the probing video signal. The emitter 5 emits a probing signal into the measuring tube 2, which, through communication transformers 8, 9, at the instants of time t _out1 and t _out2 enters the inputs of the receivers 6, 7, where the conversion into electrical signals V _out1 and V _out2 and amplification takes place. From the output of the receivers 6, 7, the signals V _out1 and V _out2 go to the input of the amplifier - shaper 11, where each of them is formed (input for microprocessor 12) video pulses, conventionally presented in the form of video pulses 1 _rad and 2 _rad respectively in Fig.2b.

The sounding signal, having reached the surface of the liquid and reflected from it, again through the connection transformers 9, 8 at the instants of time t _OTP2 and t _OTR1 goes to the inputs of the receivers 7, 6, respectively, where the received reflected signals V _OTR2 and V _OTR1 , similar to the probing ones, after conversion and the gain applied to the input of the amplifier - shaper 11, where each of them is also the input video pulses formed by the microprocessor 12 conventionally provided in the form of video pulses 2 and 1 _{Neg Neg} 2b respectively.

1 _rad video pulses; 2 _rad; 2 _neg and 1 _neg arrive at the information input of microprocessor 12, which measures the following time intervals:
- the reference (first) corresponding to the time interval t _{0 rad} = t - t _izl1 (see Figure 2c..);
- measured, corresponding to the time interval t _x = t _spr2 - t _outl1 (see Fig. 2d);
- reference (second), corresponding to the time interval t ' _o = t _otr1 - t _otr2 (see Fig. 2e).

After the fourth pulse (see pulse 1 _OTP in Fig. 2c) is received at the information input of microprocessor 12, it is forbidden to receive any information from this input until the next trigger signal is generated. The inhibit signal is conventionally shown in FIG. 2e.

где L - расстояние от второго приемника 7 до дна резервуара 1; l₀ - фиксированное расстояние между первым и вторым приемниками 6, 7; N - количество отсчетов, по которым проводится усреднение результатов измерения уровня; t_xi - временной интервал между зондирующим и отраженным сигналами, принятыми вторым приемником в i - м измерении; t_oi - временной интервал между приемом зондирующего сигнала первым и вторым приемниками в i - м измерении; t'_oi - временной интервал между приемом отраженного сигнала вторым и первым приемниками в i - м измерении.The microprocessor 12 determines the duration of time intervals t ₀ , t _x , t ' _o and calculates the liquid level l _W by the formula

where L is the distance from the second receiver 7 to the bottom of the tank 1; l ₀ - a fixed distance between the first and second receivers 6, 7; N is the number of samples over which the level measurement results are averaged; t _xi is the time interval between the probing and reflected signals received by the second receiver in the i-th dimension; t _oi is the time interval between the reception of the sounding signal by the first and second receivers in the i-th dimension; t ' _oi is the time interval between the reception of the reflected signal by the second and first receivers in the i-th dimension.

 The measurement result from the second output of the microprocessor 12 is fed to the input of the indicator 13, and from the third output to the input of external devices, such as computers, information collection, control systems, etc.

 To reduce the reaction time to measuring the liquid level, information is displayed on the indicator after each probe pulse, and the level is determined by the above formula for the N last measurement results.

 The proposed device allows the measured level to determine the volume and mass of liquid in the tank according to the passport data of the tank and the density of the liquid entered in the processor ROM, as well as determine the current flow rate (intake) of the liquid in the tanks and trays according to the specified level-flow algorithm.

Improving the accuracy of the measurement results in this device is achieved as follows:
- the measured time intervals t _oi , t _xi and t ' _oi are related to the corresponding distances between both receivers and between the second receiver and the surface of the liquid by known expressions:
t _oi = t ' _oi = l ₀ / V _oi and t _xi = 2l _x / V _xi ,
where V _oi and V _xi are the values of the speed of sound in the measuring tube in its sections between the first and second receivers and between the second receiver and the liquid level in the ith measurement, respectively.

а значит, и расчетное выражение для определения уровня жидкости l_ж практически не зависит от внешних условий;
- при измерении суммарного эталонного временного интервала (t_o + t'_o) для излученных и отраженных сигналов исключается погрешность установки обоих приемников, являющаяся источником систематической погрешности измерения уровня. Действительно, моменты появления сигналов на входах приемников можно представить следующим образом (см. фиг. 3):
t_изл1= t₁+Δt₁;
t_изл2= t₁+t_эт+Δt₂;
t_отр2= t₁+t_эт+t_x+Δt₂;
t_отр1= t₁+t_эт+t_x+t_эт+Δt₁.
где t₁ - временной интервал прохождения сигнала от излучателя до плоскости расположения первого приемника; t_эт - временной интервал происхождения сигналов от плоскости расположения первого приемника до плоскости расположения второго приемника; t_x - временной интервал происхождения сигнала от плоскости расположения второго приемника до плоскости отражения жидкостью и обратно: Δt₁ и Δt₂ - временные интервалы прохождения сигналов от плоскости расположения первого и второго приемников до их входных устройств соответственно.The presence of holes 4 in the upper part of the measuring tube 2 leads to the fact that it establishes the ratio of sound velocities V _xi / V _oi , the value of which is practically independent of external conditions and is close to unity (due to the commensurability of the lengths of the sections l _x and l ₀ ) . In this case, the ratio

and therefore, the calculated expression for determining the liquid level l _w practically does not depend on external conditions;
- when measuring the total reference time interval (t _o + t ' _o ) for the emitted and reflected signals, the installation error of both receivers is eliminated, which is the source of the systematic level measurement error. Indeed, the moments of the appearance of signals at the inputs of the receivers can be represented as follows (see Fig. 3):
t _outl1 = t ₁ + Δt ₁ ;
t _out2 = t ₁ + t _et + Δt ₂ ;
t _ad2 = t ₁ + t _et + t _x + Δt ₂ ;
t _adr1 = t ₁ + t _et + t _x + t _et + Δt ₁ .
where t ₁ - the time interval of the signal from the emitter to the plane of the first receiver; t _et - the time interval of the origin of the signals from the plane of the first receiver to the plane of the second receiver; t _x is the time interval of the signal origin from the plane of the second receiver to the plane of reflection by liquid and vice versa: Δt ₁ and Δt ₂ are the time intervals of the passage of signals from the plane of the first and second receivers to their input devices, respectively.

а их сумма очевидным образом не зависит от расстояния между осевой линией измерительной трубы и чувствительным элементом каждого приемника, что помимо снижения систематической для каждого образца погрешности измерений улучшает технологичность устройства.The measured intervals t _o and t ' _{o are} determined by the expressions:
t _o = t _out2 -t _out1 = t _et + Δt ₂ -Δt ₁ ;

and their sum obviously does not depend on the distance between the axial line of the measuring tube and the sensing element of each receiver, which, in addition to reducing the systematic measurement error for each sample, improves the manufacturability of the device.

 Improving the reliability of measurements, reducing the influence of internal and external interference, versatility in this device is achieved by using a sound guide that is matched with the emitter, and installing receivers on its outer wall, which completely eliminates the possibility of additional reflected signals, and also reduces the energy consumption of the entire device.

 Thus, the proposed device for measuring the level of liquid media provides improved accuracy and reliability of the measurement results, maintains operability in conditions of external acoustic noise, is technologically advanced and has low power consumption.

 In addition, the proposed device is versatile due to the possibility of using in tanks and trays for various purposes, including with moving liquids, the ability to change the material of the measuring tube (metal, plastic, glass, etc.) for various types of liquids, the possibility of individual adjustment source data at the installation site of the device, as well as determining the volume, mass and flow rate of the liquid.

 Currently, the layout of the device according to this invention is made and tested for its working capacity in laboratory and industrial conditions.

Claims (1)

A device for measuring the level of liquid media containing a measuring tube with an acoustic emitter of a sounding signal and a first receiver of acoustic signals, an amplifier-driver of the probing signals, an amplifier-driver of the received signals, a circuit for measuring a time interval functionally associated with the measured level, and an indicator, characterized in that a second receiver of acoustic signals is introduced into it, located below the first receiver at a fixed distance from it and above the maximum allowable ur liquid for a given tank, both receivers installed below the level of the emitter on the outer wall of the measuring tube and connected by inputs to its cavity through matching transformers, and outputs through the amplifier-driver of the received signals are connected to the signal input of the measurement circuit of the time interval functionally associated with the measured level executed on a microprocessor that implements a given program for controlling the measurement process and calculating the average value of the measured liquid level l _w in accordance with the purpose and initial data according to the formula

where L is the distance from the second receiver to the bottom of the tank;
l ₀ - fixed distance between both receivers;
N is the number of recent readings by which the results of level measurement are averaged;
t _xi is the time interval between the probing and reflected signals received by the second receiver in the i-th dimension;
t _oi is the time interval between the reception of the sounding signal by the first and second receivers in the i-th dimension;
t _oi ^' is the time interval between the reception of the reflected signal by the second and first receivers in the i-th dimension,
the first output of the microprocessor synchronizing is connected to the control input of the amplifier-driver of the probing video signals, the output of which is connected to an acoustic emitter, the second output of the microprocessor, information, is connected to the input of the indicator of the measured level, and the third output is used to communicate with external devices.

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