CN112539805B - Ultrasonic liquid level measurement system and method for sound velocity compensation by adopting DTS - Google Patents
Ultrasonic liquid level measurement system and method for sound velocity compensation by adopting DTS Download PDFInfo
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- CN112539805B CN112539805B CN202011382323.3A CN202011382323A CN112539805B CN 112539805 B CN112539805 B CN 112539805B CN 202011382323 A CN202011382323 A CN 202011382323A CN 112539805 B CN112539805 B CN 112539805B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/296—Acoustic waves
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses an ultrasonic liquid level measurement system and a method for compensating sound velocity by adopting DTS, wherein the system mainly comprises the following components: the device comprises an ultrasonic probe, a wave guide tube, a transmitting circuit, a receiving circuit, a controller, a DTS optical fiber temperature sensing module and a display module; when the ultrasonic probe works, ultrasonic waves are emitted to the measured liquid level, reflected by the liquid level and then received by the probe, and the propagation time of ultrasonic signals is calculated; the temperature of different heights in the closed container is continuously measured by using the DTS temperature sensing module, so that a sound velocity curve is calculated, and the liquid level height in the container is calculated by using the propagation time and the sound velocity curve and is displayed and stored. The ultrasonic liquid level measurement method adopting DTS to carry out sound velocity compensation can compensate the influence of temperature on the measurement precision of the ultrasonic liquid level meter, realize high-precision liquid level measurement, can be used for liquid level measurement of corrosive liquid, and has wider application occasions.
Description
Technical Field
The invention belongs to the technical field of liquid level detection, and particularly relates to an ultrasonic liquid level measurement system and method for performing sound velocity compensation by adopting DTS distributed optical fiber temperature measurement.
Background
The liquid level measurement is widely applied to industries such as petroleum, chemical industry and the like, and is the most commonly used measurement parameter in industrial production. The liquid level measuring method can be divided into a contact type and a non-contact type according to whether the liquid level measuring device is in contact with the medium to be measured. The sensing part of the contact type liquid level meter is contacted with the liquid to be measured, is not suitable for liquid level measurement under the strong acid and strong alkali corrosion radiation condition, and mainly comprises a manual liquid level meter, a float liquid level meter, a capacitive liquid level meter, a magnetostrictive liquid level meter and the like; the non-contact type liquid level measurement generally utilizes time difference to measure the liquid level, and a sensing part is not contacted with the measured liquid, so that the non-contact type liquid level measurement can be used for liquid level measurement in special occasions and mainly comprises an ultrasonic liquid level meter, a radar liquid level meter, a laser liquid level meter and the like.
Compared with other types of liquid level meters, the ultrasonic liquid level meter has the advantages of non-contact measurement, strong adaptability, capability of working in severe environments, strong universality, no abrasion, long service life and the like, and is suitable for liquid level measurement in a closed container. However, the ultrasonic sound velocity is greatly influenced by the environment, and the change of the temperature, humidity, pressure or composition of a transmission medium can influence the sound velocity, wherein the temperature influence is the greatest, and the sound velocity needs to be corrected by a temperature compensation method so as to improve the measurement accuracy of the ultrasonic liquid level meter. At present, the sound velocity compensation in the ultrasonic liquid level meter mainly adopts a single-point temperature measurement method to measure the temperature of the environment where an instrument is positioned, and the method is suitable for occasions with stable and uniform environment temperature, and for a closed container in a special environment, the temperature of liquid can be higher or lower than the environment temperature, so that the temperature of air in the container is layered, and only the temperature of a single point is obviously measured, the sound velocity change in the whole space range cannot be accurately compensated, and the high-precision liquid level measurement cannot be realized.
Therefore, it is a need for a solution to the problem of providing an ultrasonic level gauge that compensates for the speed of sound over the full spatial range.
Disclosure of Invention
The invention aims to overcome the defects, and provides an ultrasonic liquid level measurement system and method for DTS sound velocity compensation, which adopt a DTS (distributed optical fiber temperature sensing system) to realize real-time temperature measurement in a full space range by utilizing sensitivity of back scattered light in an optical fiber to temperature, so that accurate temperature measurement is carried out in the full space range of a closed container, sound velocity can be compensated in real time according to temperatures in different positions in the container, and high-precision liquid level measurement is realized.
In order to achieve the above purpose, the present invention provides the following technical solutions:
an ultrasonic liquid level measurement system employing DTS for sound velocity compensation, comprising: the device comprises an ultrasonic probe, a wave guide tube, a transmitting circuit, a receiving circuit, a controller, a DTS optical fiber temperature sensing module and a display module; wherein:
ultrasonic probe: receiving a pulse signal input by a transmitting circuit, generating an ultrasonic signal under the action of the pulse signal, and transmitting the ultrasonic signal to the liquid level through a wave guide pipe; receiving liquid level reflection ultrasonic waves returned by the wave guide pipe, realizing the mutual conversion between the liquid level reflection ultrasonic waves and the voltage signals, and outputting the voltage signals to the receiving circuit;
a waveguide: transmitting an ultrasonic signal generated by the ultrasonic probe to the liquid level, and transmitting ultrasonic waves reflected by the liquid level to the ultrasonic probe again; transmitting circuit: amplifying the pulse signal input by the controller and outputting the amplified pulse signal to the ultrasonic probe;
the receiving circuit: amplifying, filtering, detecting and shaping the voltage signal input by the ultrasonic probe to generate an interrupt signal and outputting the interrupt signal to the controller;
and (3) a controller: outputting a pulse signal to a transmitting circuit and starting timing; receiving an interrupt signal input by a receiving circuit, stopping timing, recording the time from starting timing to stopping timing as a time signal of ultrasonic wave propagation, and outputting the time signal to a DTS optical fiber temperature sensing module;
DTS fiber temperature sensing module: receiving ultrasonic wave propagation time signals input by a controller, measuring temperatures at different heights in a closed container, calculating sound velocity according to the measured temperatures, calculating a liquid level value by combining the ultrasonic wave propagation time signals and the sound velocity, and outputting the liquid level value to a display module;
and a display module: and receiving and displaying the liquid level value input by the DTS temperature sensing module.
Further, the transmitting circuit is an amplitude amplifying circuit.
Further, the ultrasonic probe is a piezoelectric ultrasonic transducer.
Further, the wave guide tube is a hollow rigid cylinder sleeved at the lower end of the ultrasonic probe, and the length of the wave guide tube is smaller than or equal to the height in the container;
further, the receiving circuit comprises an amplifying circuit, a filter circuit, an envelope detection circuit and a shaping circuit, wherein the output end of the ultrasonic probe is connected with the input end of the amplifying circuit, the output end of the amplifying circuit is connected with the input end of the filter circuit, the output end of the filter circuit is connected with the input end of the envelope detection circuit, the output end of the envelope detection circuit is connected with the input end of the shaping circuit, and the output end of the shaping circuit is connected with the input end of the controller.
Further, the DTS optical fiber temperature sensing module comprises a laser, a wavelength division multiplexer, a first photoelectric conversion circuit, a second photoelectric conversion circuit, an A/D acquisition module, an upper computer, a data storage module and a sensing optical fiber;
the output end of the laser is connected with the input end of the wavelength division multiplexer, the wavelength division multiplexer is connected with the sensing optical fiber through a bidirectional port, the first output end and the second output end of the wavelength division multiplexer are respectively connected with the input ends of the photoelectric conversion circuit I and the photoelectric conversion circuit II, the output ends of the photoelectric conversion circuit I and the photoelectric conversion circuit II are both connected with the input end of the A/D acquisition module, the output end of the A/D acquisition module is connected with the input end of the upper computer, the output end of the upper computer is connected with the input end of the data storage module, and the output end of the upper computer is connected with the display module;
the sensing optical fibers are arranged on the outer surface of the wave guide tube in parallel along the axis from bottom to top, and signals are returned to the echo division multiplexer after being transmitted through the sensing optical fibers.
An ultrasonic liquid level measurement method adopting DTS to carry out sound velocity compensation comprises the following steps:
the controller generates a pulse signal and starts timing, the pulse signal is input into the transmitting circuit, and the transmitting circuit drives the ultrasonic probe to transmit an ultrasonic signal to the measured liquid level through the wave guide tube;
s2, receiving echo signals reflected by the measured liquid level by the ultrasonic probe through the wave guide tube, generating interrupt signals after entering the receiving circuit, and stopping timing by the controller;
s3, the controller calculates the propagation time of the ultrasonic signal and transmits the propagation time to the DTS optical fiber temperature sensing module;
s4, the DTS optical fiber temperature sensing module acquires a temperature value in the closed container in real time, sound velocity can be calculated according to the temperature value, the liquid level height in the container can be obtained by combining the propagation time information obtained in the step S3, and the liquid level height is displayed in real time through the display module.
Further, in the step S4, the DTS optical fiber temperature sensing module includes a laser, a wavelength division multiplexer, a first photoelectric conversion circuit, a second photoelectric conversion circuit, an a/D acquisition module, an upper computer, a data storage module and a sensing optical fiber;
the specific steps of the DTS optical fiber temperature sensing module for acquiring the temperature value are as follows:
s41, a laser emits a pulse laser signal, a trigger signal is provided for an A/D acquisition module, and the A/D acquisition module starts acquisition;
s42, the pulse laser signals enter a sensing optical fiber after passing through a wavelength division multiplexer;
s43, backward scattered light generated by the propagation of the pulse laser signal in the sensing optical fiber is divided into anti-Stokes light and Stokes light after passing through the wavelength division multiplexer, and the anti-Stokes light and the Stokes light enter the photoelectric receiving conversion circuit I and the photoelectric receiving conversion circuit II respectively to complete photoelectric conversion and signal amplification processing to obtain voltage signals V1 and V2;
s44, the voltage signals V1 and V2 enter an A/D acquisition module, and the A/D acquisition module completes accumulation and average processing of the acquisition signals to obtain acquisition signals Vd1 and Vd2;
s45Vd1 and Vd2 enter the upper computer, demodulate the temperature information in the container and transmit to the data storage module for storage.
Further, in the above step S4, the formula of calculating the sound velocity from the temperature is v=331.45+0.607T, where v is the ultrasonic sound velocity and T is the ambient temperature.
Further, the information of the liquid level in the above step S4 is obtained by the formula h=l-v·t/2, where v represents the ultrasonic sound velocity, t is the propagation time of the ultrasonic wave, H is the liquid level, and L is the total height in the container.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the ultrasonic liquid level sensing system for performing sound velocity compensation by adopting the DTS, the distributed optical fiber temperature sensing system is combined with the ultrasonic liquid level meter, so that continuous measurement of partial temperature of a gas transmission medium in the closed container is realized, the influence of the temperature on the measurement precision of the ultrasonic liquid level meter is greatly reduced, and meanwhile, compared with the sound velocity compensation for single-point temperature measurement, the ultrasonic liquid level sensing system can more accurately compensate the sound velocity of ultrasonic waves and realize high-precision liquid level measurement;
(2) The distributed optical fiber temperature sensing technology adopted by the invention uses the optical fiber as a sensing element, has strong electromagnetic interference resistance, long transmission distance, strong corrosion resistance and good durability, can be used for measuring the liquid level of corrosive liquid, and is more widely applicable to occasions;
(3) The invention adopts the wave guide pipe structure, so that the ultrasonic wave can only propagate and emit in the pipe, the interference of stray reflected wave can be reduced, the influence of steam in the container on ultrasonic liquid level measurement can be restrained to a certain extent, and the liquid level measurement precision is improved.
Drawings
FIG. 1 is a schematic diagram of the ultrasonic level gauge measurement provided by the invention.
Fig. 2 is a schematic diagram of an ultrasonic liquid level sensing system adopting DTS for sound velocity compensation according to the present invention.
Fig. 3 is a schematic diagram of a receiving circuit according to the present invention.
Fig. 4 is a schematic structural diagram of a DTS optical fiber temperature sensing system provided by the invention.
FIG. 5 is a flow chart of the operation of the ultrasonic liquid level sensing system using DTS for sound velocity compensation according to the present invention.
Fig. 6 is a schematic diagram of a DTS optical fiber temperature sensing operation flow chart provided by the invention.
The device comprises a 1 ultrasonic probe, a 2 wave guide tube, a 3 transmitting circuit, a 4 receiving circuit, a 401 amplifying circuit, a 402 filtering circuit, a 403 envelope detection circuit, a 404 shaping circuit, a 5 controller, a 6DTS optical fiber temperature sensing module, a 601 laser, a 602 wavelength division multiplexer, a 603 photoelectric receiving and converting circuit I, a 604 photoelectric receiving and converting circuit II, a 605A/D collecting module, a 606 upper computer, a 607 data storage module, a 7 display module and an 8 sensing optical fiber.
Detailed Description
The features and advantages of the present invention will become more apparent and clear from the following detailed description of the invention.
The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are illustrated in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
As shown in fig. 2, an ultrasonic liquid level sensing system for sound velocity compensation using DTS includes: an ultrasonic probe 1, a wave guide tube 2, a transmitting circuit 3, a receiving circuit 4, a controller 5, a DTS optical fiber temperature sensing module 6 and a display module 7;
the controller 5, the transmitting circuit 3 and the ultrasonic probe 1 are connected in sequence, the wave guide tube 2 is arranged below the ultrasonic probe, the ultrasonic probe 1 generates ultrasonic pulse signals, the ultrasonic pulse signals are transmitted in the wave guide tube 2 and are emitted to the tested liquid level, meanwhile, the ultrasonic probe 1 detects the reflected ultrasonic signals, and after the mutual conversion of the ultrasonic signals and the voltage signals is realized, the voltage signals are transmitted to the receiving circuit 4; the wave guide tube 2 is used for reducing the influence of stray reflected waves on ultrasonic detection and reducing the influence of steam in the container on liquid level measurement; because the ultrasonic probe needs high-voltage pulse excitation to generate ultrasonic waves, the transmitting circuit 3 is used for amplifying pulse signals output by the controller so as to enable the ultrasonic probe to emit ultrasonic waves with certain energy and capable of transmitting long distances; the receiving circuit 4 amplifies, filters, detects and shapes the voltage signal output by the ultrasonic probe, generates an interrupt signal and inputs the interrupt signal into the controller; the output end of the receiving circuit 4 is connected with the input end of the controller 5; the controller 5 is used for generating a square wave signal with fixed frequency and receiving an interrupt signal, namely, stopping a timing signal, and calculating the propagation time of ultrasonic waves; the output end of the controller 5 is connected with the input end of the DTS optical fiber temperature sensing module 6, the output end of the DTS optical fiber temperature sensing module 6 is connected with the input end of the display module 7, the DTS optical fiber temperature sensing module 6 is used for continuously measuring temperatures at different heights in the closed container, calculating sound velocity according to the measured temperatures, compensating the influence of the temperatures on the sound velocity, calculating a liquid level value by combining the ultrasonic propagation time calculated by the controller, and improving the measuring precision of the liquid level meter; the display module 7 is used for displaying the liquid level measurement result calculated and processed by the DTS temperature sensing module.
As shown in fig. 1, the distance measurement principle of the ultrasonic liquid level meter is that, when in operation, the ultrasonic probe emits pulse ultrasonic waves to the liquid surface, the ultrasonic waves are emitted at the interface between gas and liquid, reflected echo signals are returned and received by the ultrasonic probe, the ultrasonic liquid level meter calculates a time difference t according to the recorded pulse emission time and echo receiving time, calculates a distance value between the liquid surface and the top end of the closed container according to a formula h=v·t/2, and then calculates a liquid level value in the container according to a formula h=l-v·t/2, wherein H is the distance between the top end of the closed container and the liquid surface, H is the liquid level height, and L is the total height in the container.
Further, the transmitting circuit 3 is an amplitude amplifying circuit.
Further, the ultrasonic probe is a piezoelectric ultrasonic transducer.
Furthermore, the wave guide tube 2 is a hollow rigid cylinder, can be sleeved at the lower end of the ultrasonic probe, and has the length smaller than or equal to the height in the container;
further, as shown in fig. 3, the receiving circuit 4 includes an amplifying circuit 401, a filtering circuit 402, an envelope detection circuit 403, and a shaping circuit 404, where an output end of the ultrasonic probe 1 is connected to an input end of the amplifying circuit 401, an output end of the amplifying circuit 401 is connected to an input end of the filtering circuit 402, an output end of the filtering circuit 402 is connected to an input end of the envelope detection circuit 403, an output end of the envelope detection circuit 403 is connected to an input end of the shaping circuit 404, and an output end of the shaping circuit 404 is connected to an input end of the controller 5.
Further, as shown in fig. 4, the DTS optical fiber temperature sensing module 6 includes a laser 601, a wavelength division multiplexer 602, a first photoelectric conversion circuit 603, a second photoelectric conversion circuit 604, an a/D acquisition module 605, an upper computer 606, a data storage module 607 and a sensing optical fiber 8;
the output end of the laser 601 is connected with the input end of the wavelength division multiplexer 602, the first output end and the second output end of the wavelength division multiplexer 602 are respectively connected with the input ends of the first photoelectric conversion circuit 603 and the second photoelectric conversion circuit 604, the output ends of the first photoelectric conversion circuit 603 and the second photoelectric conversion circuit 604 are both connected with the input end of the A/D acquisition module 605, the output end of the A/D acquisition module 605 is connected with the input end of the upper computer 606, the output end of the upper computer 606 is connected with the input end of the data storage module 607, and the output end of the upper computer 606 is connected with the display module 7;
the sensing optical fiber 8 is a sensing element of the DTS optical fiber temperature sensing module and is used for sensing the change of the external temperature and transmitting the optical signal modulated by the temperature. The bidirectional port of the wavelength division multiplexer 602 is connected with a sensing optical fiber 8, the sensing optical fiber 8 is arranged on the outer surface of the waveguide tube 2 in parallel along the axis from bottom to top, and the signal is transmitted by the sensing optical fiber 8 and then returned to the wavelength division multiplexer 602.
The invention discloses an ultrasonic liquid level measurement method for compensating sound velocity by adopting DTS, which comprises the following steps:
the controller 5 generates a pulse signal and starts timing, the pulse signal is input into the transmitting circuit 3 to drive the ultrasonic probe to transmit an ultrasonic signal to the measured liquid level through the wave guide tube 2;
s2, an echo signal reflected by the measured liquid level is received by the ultrasonic probe 1 through the wave guide tube 2, an interrupt signal is generated after the echo signal enters the receiving circuit 4, and the controller 5 stops timing;
s3, the controller 5 calculates the propagation time of the ultrasonic signal and transmits the propagation time to the DTS optical fiber temperature sensing module 6;
s4, the DTS optical fiber temperature sensing module 6 acquires a temperature value in the closed container in real time, sound velocity can be calculated according to the temperature value, the liquid level height in the container can be obtained by combining the propagation time information obtained in the step S3, and the liquid level height is displayed in real time through the display module 7;
8. the ultrasonic liquid level measurement method using DTS for sound velocity compensation according to claim 7, wherein in step S4, the DTS optical fiber temperature sensing module 6 includes a laser 601, a wavelength division multiplexer 602, a first photoelectric conversion circuit 603, a second photoelectric conversion circuit 604, an a/D acquisition module 605, an upper computer 606, a data storage module 607, and a sensing optical fiber 8;
the specific steps of the DTS optical fiber temperature sensing module for acquiring the temperature value are as follows:
s41, a laser 601 emits a pulse laser signal, a trigger signal is provided for an A/D acquisition module 605, and the A/D acquisition module 605 starts acquisition;
s42, the pulse laser signal enters the sensing optical fiber 8 after passing through the wavelength division multiplexer 602;
the backward scattered light generated by the propagation of the S43 pulse laser signal in the sensing optical fiber 8 is divided into anti-Stokes light (AS light) and Stokes light (S light) through the wavelength division multiplexer 602, and the anti-Stokes light (AS light) and the Stokes light enter the photoelectric receiving and converting circuit I603 and the photoelectric receiving and converting circuit II 604 respectively to complete photoelectric conversion and signal amplification processing to obtain voltage signals V1 and V2; the back scattered light is back Raman scattered light, raman scattering occurs when the light pulse propagates in the optical fiber, the Raman scattered light returned along the optical fiber is called back Raman scattered light, and the back Raman scattered light intensity is related to the temperature of a scattering point;
s44, voltage signals V1 and V2 enter an A/D acquisition module 605, and the A/D acquisition module 605 completes accumulation and average processing of the acquisition signals to obtain acquisition signals Vd1 and Vd2;
s45Vd1 and Vd2 enter the host computer 606, demodulate the temperature information in the container, and transmit to the data storage module 607 for storage.
Further, in step S4, the formula of calculating the sound velocity from the temperature is v=331.45+0.607T, where v is the ultrasonic sound velocity and T is the ambient temperature.
Further, the information of the liquid level in step S4 is obtained by the formula h=l-v·t/2, where v represents the ultrasonic sound velocity, t is the propagation time of the ultrasonic wave, H is the liquid level, and L is the total height in the container.
Example 1
Referring to fig. 5, an ultrasonic liquid level sensing system and method for sound velocity compensation using DTS includes the steps of:
the system S1 is electrified, the ultrasonic probe 1 is of a T/R40-16 type, the optimal performance can be exerted only under the drive of 40kHz voltage, the controller 5, namely the singlechip, sends out square waves with the frequency of 40kHz and starts timing, the square waves enter the transmitting circuit 3, and the transmitting circuit 3 amplifies the power and the amplitude of square wave signals generated by the controller to excite the ultrasonic probe to transmit ultrasonic signals;
s2, an ultrasonic signal reflected by a measured liquid level is converted into a voltage signal V through the ultrasonic probe 1, the voltage signal V enters the receiving circuit 4, and because the voltage signal output by the ultrasonic probe 1 is weak, the signal VA is obtained by amplifying the voltage signal V through the amplifying circuit 401, the signal VA is processed through the filtering circuit, the signal VF is obtained after low-frequency noise is removed, the voltage signal VF is subjected to envelope detection through the detection circuit 403, the obtained voltage signal VD enters the shaping circuit 404, the shaping circuit 404 is built through a comparator, the threshold voltage is set to be Vth, when the amplitude of the signal VD is larger than the threshold voltage Vth, the output end of the shaping circuit outputs a high level, otherwise, the voltage signal V is output a low level, so that the analog voltage signal VD can be shaped into a digital square wave signal VS, an interrupt signal is provided for the controller 5, and the controller 5 stops timing;
s3, the signal VS is used as an interrupt signal to enter the controller 5, the controller 5 stops timing, the propagation time of the ultrasonic signal is calculated, and the time calculated value is transmitted to the upper computer 606 of the DTS optical fiber temperature sensing module 6 through a serial port;
s4, because temperature layering phenomenon possibly exists in temperatures of different heights in a container, a DTS optical fiber temperature sensing module 6 continuously measures temperature values of different heights in a closed container through optical fibers to obtain temperature curves of different heights in the container, an upper computer finds out a point with larger gradient change of the temperature curve through an algorithm to serve as a critical surface of gas and liquid, a temperature point above an interface is taken to calculate sound velocity v=331.45+0.607T, wherein T represents the ambient temperature, the sound velocity curve of a gas part is fitted, the sound velocity curve is subjected to integral calculation by utilizing a time value measured by a controller 5 in the step S3 and utilizing a formula h=v.t/2, the distance value between the measured liquid level and the top end of the container is obtained, the liquid level height is calculated by carrying in the formula H=L-v.t/2, H is the distance between the measured liquid level and the top end of the container, L is the total height in the container, v is the ultrasonic sound velocity, and T is the ultrasonic propagation time;
and S5, the upper computer 606 transmits the calculated liquid level value to the data storage module 607 for storage, and transmits the liquid level data to the display module 7 for display.
Referring to fig. 6, the temperature measurement steps of the dts optical fiber temperature sensing module are as follows:
after the S41 system is powered on, the laser 601 emits a pulse laser signal with the wavelength of 1550 nm;
s42 pulse laser signals enter the sensing optical fiber 8 after passing through the wavelength division multiplexer 602, backward scattered light sensitive to temperature is generated in the process of laser light propagation in the sensing optical fiber 8, and the backward scattered light enters the wavelength division multiplexer 602 and is divided into two paths, wherein one path is anti-Stokes light (AS light) with the wavelength of 1450nm, and the other path is Stokes light (S light) with the wavelength of 1663 nm;
s43, the wavelength division multiplexer 602 outputs AS light to enter the first photoelectric receiving and converting circuit 603, the first photoelectric receiving and converting circuit converts the AS light signal into a voltage signal, and amplifies the voltage signal to meet the input requirement of the A/D acquisition module to obtain a voltage signal V1; the S light output by the wavelength division multiplexer 602 enters a second photoelectric receiving and converting circuit 604, the second photoelectric receiving and converting circuit converts the S light signal into a voltage signal, and amplifies the voltage signal to meet the input requirement of the A/D acquisition module 605 to obtain a voltage signal V2;
s44 laser 601 provides synchronous trigger signal for A/D acquisition module 605 while transmitting pulse laser signal, and A/D acquisition module 605 starts acquisition; the voltage signal V1 and the voltage signal V2 respectively enter an A/D acquisition module 605, the A/D acquisition module 605 completes analog-to-digital conversion and signal acquisition of V1 and V2, and the acquired digital signals are accumulated and averaged to obtain digital signals Vd1 and Vd2 respectively;
the digital signals Vd1 and Vd2 output by the S45A/D acquisition module are transmitted to the upper computer 606, the upper computer 606 performs demodulation operation to obtain a temperature curve in the container, and the data is transmitted to the data storage module 607 for storage.
The ultrasonic liquid level measurement system and the ultrasonic liquid level measurement method adopting the DTS for sound velocity compensation provided by the invention reduce the problem that the ultrasonic liquid level measurement precision is greatly influenced by the ambient temperature, improve the system measurement precision, and are simultaneously suitable for the liquid level measurement of corrosive liquid.
The invention has been described in detail in connection with the specific embodiments and exemplary examples thereof, but such description is not to be construed as limiting the invention. It will be understood by those skilled in the art that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, and these fall within the scope of the present invention. The scope of the invention is defined by the appended claims.
What is not described in detail in the present specification is a well known technology to those skilled in the art.
Claims (8)
1. An ultrasonic liquid level measurement system employing DTS for sound velocity compensation, comprising: an ultrasonic probe (1), a wave guide tube (2), a transmitting circuit (3), a receiving circuit (4), a controller (5), a DTS optical fiber temperature sensing module (6) and a display module (7); wherein:
ultrasonic probe (1): receiving a pulse signal input by a transmitting circuit (3), generating an ultrasonic signal under the action of the pulse signal, and transmitting the ultrasonic signal to the liquid level through a wave guide pipe (2); receiving liquid level reflection ultrasonic waves returned by the wave guide pipe (2), realizing the mutual conversion between the liquid level reflection ultrasonic waves and voltage signals, and outputting the voltage signals to the receiving circuit (4);
waveguide (2): transmitting an ultrasonic signal generated by the ultrasonic probe (1) to the liquid surface, and transmitting ultrasonic waves reflected by the liquid surface to the ultrasonic probe (1);
transmitting circuit (3): amplifying the pulse signal input by the controller (5) and outputting the amplified pulse signal to the ultrasonic probe (1);
receiving circuit (4): amplifying, filtering, detecting and shaping the voltage signal input by the ultrasonic probe (1), generating an interrupt signal and outputting the interrupt signal to the controller (5);
controller (5): outputting a pulse signal to a transmitting circuit (3) and starting timing; receiving an interrupt signal input by a receiving circuit (4) and stopping timing, recording the time between starting and stopping timing as a time signal of ultrasonic wave propagation, and outputting the time signal to a DTS optical fiber temperature sensing module (6);
DTS fiber temperature sensing module (6): receiving ultrasonic wave propagation time signals input by a controller (5), measuring temperatures at different heights in the closed container, calculating sound velocity according to the measured temperatures, calculating a liquid level value by combining the ultrasonic wave propagation time signals and the sound velocity, and outputting the liquid level value to a display module (7);
display module (7): receiving and displaying a liquid level value input by a DTS optical fiber temperature sensing module (6);
the DTS optical fiber temperature sensing module (6) comprises a laser (601), a wavelength division multiplexer (602), a photoelectric receiving and converting circuit I (603), a photoelectric receiving and converting circuit II (604), an A/D acquisition module (605), an upper computer (606), a data storage module (607) and a sensing optical fiber (8);
the output end of the laser (601) is connected with the input end of the wavelength division multiplexer (602), the wavelength division multiplexer (602) is connected with the sensing optical fiber (8) through a bidirectional port, the first output end and the second output end of the wavelength division multiplexer (602) are respectively connected with the input ends of the photoelectric receiving conversion circuit I (603) and the photoelectric receiving conversion circuit II (604), the output ends of the photoelectric receiving conversion circuit I (603) and the photoelectric receiving conversion circuit II (604) are both connected with the input end of the A/D acquisition module (605), the output end of the A/D acquisition module (605) is connected with the input end of the upper computer (606), the output end of the upper computer (606) is connected with the input end of the data storage module (607), and the output end of the upper computer (606) is connected with the display module (7);
the sensing optical fiber (8) is arranged on the outer surface of the wave guide tube (2) in parallel along the axis from bottom to top, and signals are returned to the echo division multiplexer (602) after being transmitted by the sensing optical fiber (8);
the specific steps of the DTS optical fiber temperature sensing module for acquiring the temperature value are as follows:
s41, a laser (601) emits a pulse laser signal, a trigger signal is provided for an A/D acquisition module (605), and the A/D acquisition module (605) starts acquisition;
s42 pulse laser signals enter a sensing optical fiber (8) after passing through a wavelength division multiplexer (602);
s43, backward scattered light generated by the propagation of the pulse laser signal in the sensing optical fiber (8) is divided into anti-Stokes light and Stokes light after passing through the wavelength division multiplexer (602), and the anti-Stokes light and the Stokes light enter the photoelectric receiving and converting circuit I (603) and the photoelectric receiving and converting circuit II (604) respectively to finish photoelectric conversion and signal amplification processing to obtain voltage signals V1 and V2; the back scattered light is back Raman scattered light, raman scattering occurs when the light pulse propagates in the optical fiber, the Raman scattered light returned along the optical fiber is called back Raman scattered light, and the back Raman scattered light intensity is related to the temperature of a scattering point;
s44, the voltage signals V1 and V2 enter an A/D acquisition module (605), and the A/D acquisition module (605) completes accumulation and average processing of the acquisition signals to obtain acquisition signals Vd1 and Vd2;
s45Vd1 and Vd2 enter an upper computer (606), demodulate the temperature information in the container and transmit the temperature information to a data storage module (607) for storage.
2. An ultrasonic liquid level measurement system employing DTS for sound velocity compensation according to claim 1, wherein the transmitting circuit (3) is an amplitude amplifying circuit.
3. An ultrasonic level measurement system employing DTS for sound velocity compensation according to claim 1, wherein the ultrasonic probe (1) is a piezoelectric ultrasonic transducer.
4. An ultrasonic liquid level measurement system using DTS for sound velocity compensation according to claim 1, wherein the waveguide (2) is a hollow rigid cylinder, which is sleeved at the lower end of the ultrasonic probe (1) and has a length equal to or less than the height in the container.
5. The ultrasonic liquid level measurement system adopting the DTS for sound velocity compensation according to claim 1, wherein the receiving circuit (4) comprises an amplifying circuit (401), a filtering circuit (402), an envelope detection circuit (403) and a shaping circuit (404), the output end of the ultrasonic probe (1) is connected with the input end of the amplifying circuit (401), the output end of the amplifying circuit (401) is connected with the input end of the filtering circuit (402), the output end of the filtering circuit (402) is connected with the input end of the envelope detection circuit (403), the output end of the envelope detection circuit (403) is connected with the input end of the shaping circuit (404), and the output end of the shaping circuit (404) is connected with the input end of the controller (5).
6. An ultrasonic liquid level measurement method using DTS for sound speed compensation, characterized in that the measurement method is performed using an ultrasonic liquid level measurement system using DTS for sound speed compensation as set forth in any one of claims 1 to 5, comprising the steps of:
the controller (5) generates a pulse signal and starts timing, the pulse signal is input to the transmitting circuit (3), and the transmitting circuit (3) drives the ultrasonic probe (1) to transmit an ultrasonic signal to the measured liquid level through the wave guide pipe (2);
s2, an echo signal reflected by the measured liquid level is received by the ultrasonic probe (1) through the wave guide pipe (2), an interrupt signal is generated after the echo signal enters the receiving circuit (4), and the controller (5) stops timing;
s3, the controller (5) calculates the propagation time of the ultrasonic signal and transmits the propagation time to the DTS optical fiber temperature sensing module (6);
s4, the DTS optical fiber temperature sensing module (6) acquires a temperature value in the closed container in real time, calculates sound velocity according to the temperature value, combines the propagation time information obtained in the step S3 to obtain the liquid level height in the container, and displays the liquid level height in real time through the display module (7);
in the step S4, the DTS optical fiber temperature sensing module (6) includes a laser (601), a wavelength division multiplexer (602), a first photoelectric receiving and converting circuit (603), a second photoelectric receiving and converting circuit (604), an a/D acquisition module (605), an upper computer (606), a data storage module (607) and a sensing optical fiber (8);
the specific steps of the DTS optical fiber temperature sensing module for acquiring the temperature value are as follows:
s41, a laser (601) emits a pulse laser signal, a trigger signal is provided for an A/D acquisition module (605), and the A/D acquisition module (605) starts acquisition;
s42 pulse laser signals enter a sensing optical fiber (8) after passing through a wavelength division multiplexer (602);
s43, backward scattered light generated by the propagation of the pulse laser signal in the sensing optical fiber (8) is divided into anti-Stokes light and Stokes light after passing through the wavelength division multiplexer (602), and the anti-Stokes light and the Stokes light enter the photoelectric receiving and converting circuit I (603) and the photoelectric receiving and converting circuit II (604) respectively to finish photoelectric conversion and signal amplification processing to obtain voltage signals V1 and V2; the back scattered light is back Raman scattered light, raman scattering occurs when the light pulse propagates in the optical fiber, the Raman scattered light returned along the optical fiber is called back Raman scattered light, and the back Raman scattered light intensity is related to the temperature of a scattering point;
s44, the voltage signals V1 and V2 enter an A/D acquisition module (605), and the A/D acquisition module (605) completes accumulation and average processing of the acquisition signals to obtain acquisition signals Vd1 and Vd2;
s45Vd1 and Vd2 enter an upper computer (606), demodulate the temperature information in the container and transmit the temperature information to a data storage module (607) for storage.
7. The ultrasonic liquid level measurement method using DTS for sound velocity compensation according to claim 6, wherein in the step S4, the formula of calculating the sound velocity from the temperature is v=331.45+0.607T, where v is the ultrasonic sound velocity and T is the ambient temperature.
8. The ultrasonic liquid level measurement method using DTS for sound velocity compensation according to claim 6, wherein the information of the liquid level height in step S4 is obtained by the formula h=l-v·t/2, where v represents the ultrasonic sound velocity, t is the propagation time of the ultrasonic wave, H is the liquid level height, and L is the total height in the container.
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