CN111076793B - Ultrasonic liquid level measuring device and method special for inspection well - Google Patents

Ultrasonic liquid level measuring device and method special for inspection well Download PDF

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Publication number
CN111076793B
CN111076793B CN201911390359.3A CN201911390359A CN111076793B CN 111076793 B CN111076793 B CN 111076793B CN 201911390359 A CN201911390359 A CN 201911390359A CN 111076793 B CN111076793 B CN 111076793B
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ultrasonic
circuit
signal
frequency
filter circuit
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CN111076793A (en
Inventor
孙宝磊
张志辉
符啸宇
王志久
梁庆阳
李帅
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Richway Beijing Technology Co ltd
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Richway Beijing Technology Co ltd
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22Indicating 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
    • G01F23/28Indicating 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
    • G01F23/296Acoustic waves
    • G01F23/2962Measuring transit time of reflected waves
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/02Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
    • G01S15/06Systems determining the position data of a target
    • G01S15/08Systems for measuring distance only
    • G01S15/10Systems for measuring distance only using transmission of interrupted, pulse-modulated waves
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/523Details of pulse systems
    • G01S7/526Receivers
    • G01S7/527Extracting wanted echo signals
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/539Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

An inspection well special ultrasonic liquid level measuring device and method specifically comprise a control module, an ultrasonic probe, an amplitude limiting circuit, a passive filter circuit, a multistage band-pass filter circuit and a power detection circuit; the control module is used for generating a frequency signal with a frequency corresponding to the ultrasonic probe according to the control instruction; calculating according to the effective detection signal to obtain a measurement result; the ultrasonic probe is used for transmitting an ultrasonic detection signal with corresponding frequency to a detected area according to the amplified frequency signal and receiving a feedback ultrasonic feedback signal; the amplitude limiting circuit is used for carrying out amplitude limiting processing on the ultrasonic feedback signal; the passive filter circuit is used for filtering source-end noise in the ultrasonic feedback signal; the multistage band-pass filter circuit is used for amplifying and filtering noise of preset frequency on the ultrasonic feedback signal after the noise of the source end is filtered; the power detection circuit is used for analyzing the ultrasonic feedback signal amplified and subjected to noise filtering by the multistage band-pass filter circuit to obtain an effective detection signal.

Description

Ultrasonic liquid level measuring device and method special for inspection well
Technical Field
The invention relates to the field of measurement, in particular to an ultrasonic liquid level measuring device and method special for an inspection well.
Background
At present, the inspection well liquid level measurement generally adopts an ultrasonic level meter for measurement, and the ultrasonic level meter is generally used in occasions of solid, stable surface and stable environment and has a plurality of problems when being applied to the inspection well liquid level measurement. Specifically, the control center generally uses a microcontroller such as a single chip microcomputer or a DSP as a core, and related driving and filtering circuits are added to the periphery. The LDO or DCDC is generally adopted in the aspect of power management. The pulse amplification circuit usually adopts a transformer with a high transformation ratio or converts the voltage into a high-voltage source (generally about 1K volt) through a flyback converter, and the high-voltage source is subjected to high-voltage MOS or IGBT to realize pulse amplification. The secondary limiting circuit generally limits the voltage to about 1V by using a pair tube diode, and then enters a control center through a simple amplifier. Furthermore, the application of the transformer or the flyback converter with higher transformation ratio makes the source stage of the transformer have to adopt MOS tube or IGBT with higher voltage resistance, which makes the application of these devices more costly. Due to the extremely high transformation ratio of the transformer, the voltage is close to 1KV under the condition of load, and the problem of large EMI is often caused. And secondly, the environment in the inspection well is humid and high-temperature, so that the data stability is poor, the drift is serious, and the data precision is poor. Finally, the liquid level to be measured is mostly a fluctuating liquid level, and in addition, the barriers in the inspection well are more and the space is closed, so that ultrasonic waves in the inspection well are reflected for multiple times, the false echo is serious, and serious problems that the measurement cannot be carried out or the measured value is wrong and the like are caused.
Disclosure of Invention
The invention aims to provide an ultrasonic liquid level measuring device and method special for an inspection well, which solve the problem of EMI (electro-magnetic interference), reduce the hardware cost and solve the problems of incapability of measuring, error measured value and the like caused by civil engineering structures and the like in the inspection well.
In order to achieve the purpose, the special ultrasonic liquid level measuring device for the inspection well, which is provided by the invention, specifically comprises a control module, an ultrasonic probe, an amplitude limiting circuit, a passive filter circuit, a multistage band-pass filter circuit and a power detection circuit; the control module is used for generating a frequency signal with a frequency corresponding to the ultrasonic probe according to a control instruction; and calculating to obtain a measurement result according to the effective detection signal; the ultrasonic probe is used for transmitting an ultrasonic detection signal with corresponding frequency to a detected area according to the frequency signal and receiving a feedback ultrasonic feedback signal; the amplitude limiting circuit is connected with the ultrasonic probe and is used for carrying out amplitude limiting processing on the ultrasonic feedback signal; the passive filter circuit is connected with the amplitude limiting circuit and is used for filtering source-end noise in the ultrasonic feedback signal; the multistage band-pass filter circuit is connected with the passive filter circuit and is used for amplifying and filtering noise of preset frequency on the ultrasonic feedback signal after source-end noise is filtered; the power detection circuit is connected with the multistage band-pass filter circuit and is used for analyzing the ultrasonic feedback signal amplified and subjected to noise filtering by the multistage band-pass filter circuit to obtain an effective detection signal.
In the above ultrasonic liquid level measuring device for an inspection well, preferably, the control module includes a pulse amplifying circuit; the control module generates frequency points according to the control instruction; the pulse amplification circuit is used for generating a frequency signal with a frequency corresponding to the ultrasonic probe according to the frequency point.
In the above ultrasonic liquid level measuring device for an inspection well, preferably, the multistage band-pass filter circuit includes a program-controlled gain amplifying circuit and a first active band-pass filter circuit; the program control gain amplifying circuit is used for amplifying the ultrasonic feedback signal output by the passive filter circuit; the first active band-pass filter circuit is connected with the program-controlled gain amplifying circuit and is used for carrying out noise filtering processing of preset frequency on the amplified passive filter circuit.
In above-mentioned special ultrasonic wave liquid level measurement device of inspection shaft, preferred, the device still contains the active band-pass filter circuit of second, the active band-pass filter circuit of second set up in control module with between the power detection circuit, be used for right the effective detected signal of power detection circuit output carries out amplification processing.
In the above ultrasonic liquid level measuring device for an inspection well, preferably, the first active band-pass filter circuit and the second active band-pass filter circuit are butterworth band-pass filters.
In the above ultrasonic liquid level measuring device for an inspection well, preferably, the device further comprises a compensation circuit, the compensation circuit is connected to the control module and is used for compensating for a predetermined rule of an effective detection signal; and the control module calculates to obtain a measurement result according to the compensated effective detection signal.
In the above ultrasonic liquid level measuring device for an inspection well, preferably, the compensation circuit includes one or a combination of a sound velocity compensation module, a frequency compensation module and a malformation correction module; the sound velocity compensation module comprises a temperature and humidity sensor and an air pressure sensor, and is used for acquiring temperature data, humidity data and air pressure data of the environment where the special ultrasonic liquid level measurement device for the inspection well is located through the temperature and humidity sensor and the air pressure sensor, and calculating and obtaining sound velocity information of the current environment according to the temperature data, the humidity data and the air pressure data; the frequency compensation module is used for driving the ultrasonic probe by taking the crystal oscillator as a clock source; the deformity correction module is used for detecting a double-peak deformity signal in the effective detection signal through the hysteresis comparator, and when the double-peak deformity signal exists in the effective detection signal, the effective detection signal is corrected through the signal conversion circuit, so that the double-peak deformity in the effective detection signal is eliminated.
The invention also provides a special ultrasonic liquid level measuring method for the inspection well, which comprises the following steps: generating a frequency signal with a frequency corresponding to the ultrasonic probe according to the control instruction; transmitting ultrasonic detection signals with corresponding frequencies to a detected area according to the frequency signals, and receiving feedback ultrasonic feedback signals; carrying out amplitude limiting processing on the ultrasonic feedback signal, and filtering source-end noise in the ultrasonic feedback signal; amplifying and filtering the ultrasonic feedback signal with the source end noise filtered, and analyzing to obtain an effective detection signal; and calculating according to the effective detection signal to obtain a measurement result.
In the above method for measuring the liquid level of the ultrasonic wave specially used for the inspection well, preferably, the obtaining of the measurement result by calculating according to the effective detection signal includes: collecting temperature data, humidity data and air pressure data of the environment where the ultrasonic liquid level measuring device special for the inspection well is located; calculating to obtain sound velocity information of the current environment according to the temperature data, the humidity data and the air pressure data; and compensating the effective detection signal according to the sound velocity information, and calculating according to the compensated effective detection signal to obtain a measurement result.
In the above method for measuring the liquid level of the ultrasonic wave specially used for the inspection well, preferably, the obtaining of the measurement result by calculating according to the effective detection signal includes: the waveform of the effective detection signal is detected through an analog-to-digital converter and a malformation correction circuit respectively, and when the analog-to-digital converter detects that two peak values exist in a preset period of the effective detection signal and the detection result of the malformation correction circuit is one peak value, the measurement result is obtained through the calculation of the detection result of the malformation correction circuit.
The invention has the beneficial technical effects that: a high-sensitivity echo processing system is formed by a passive filter, a multistage band-pass filter and a logarithmic detection technology, so that partial voltage of a pulse amplification circuit is reduced, and the EMI problem is solved; the compensation circuit is utilized to obviously improve the measurement precision of the liquid level in the inspection well, realize full-scale measurement so as to adapt to the complex environment in the inspection well, restore correct echo signals and achieve the function of accurately measuring the liquid level of the inspection well.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
fig. 1 is a schematic structural view of an inspection well dedicated ultrasonic liquid level measurement device according to an embodiment of the present invention;
fig. 2 is a schematic view of an application structure of the ultrasonic liquid level measuring device for the inspection well according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a passive low-pass filter circuit according to an embodiment of the present invention;
fig. 4 is a schematic diagram illustrating a test effect of a passive low-pass filter circuit according to an embodiment of the invention;
fig. 5 is a schematic structural diagram of a bandpass filter circuit according to an embodiment of the invention;
fig. 6 is a schematic structural diagram of a pulse amplifying circuit according to an embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating an ultrasonic measurement principle provided by an embodiment of the present invention;
FIG. 8 is a schematic diagram of a crystal frequency error according to an embodiment of the present invention;
fig. 9A to 9G are schematic diagrams illustrating waveform distortion compensation according to an embodiment of the present invention;
fig. 10 is a schematic flow chart of an inspection well dedicated ultrasonic liquid level measurement method according to an embodiment of the present invention;
fig. 11A to 11E are schematic diagrams illustrating a circuit for correcting deformity and a principle thereof according to an embodiment of the invention.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, unless otherwise specified, the embodiments and features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
Additionally, the steps illustrated in the flow charts of the figures may be performed in a computer system such as a set of computer-executable instructions and, although a logical order is illustrated in the flow charts, in some cases, the steps illustrated or described may be performed in an order different than here.
Referring to fig. 1, the ultrasonic liquid level measuring device for an inspection well provided by the present invention specifically includes a control module, an ultrasonic probe, a limiting circuit, a passive filter circuit, a multi-stage band-pass filter circuit, and a power detection circuit; the control module is used for generating a frequency signal with a frequency corresponding to the ultrasonic probe according to a control instruction; and calculating to obtain a measurement result according to the effective detection signal; the ultrasonic probe is used for transmitting an ultrasonic detection signal with corresponding frequency to a detected area according to the frequency signal and receiving a feedback ultrasonic feedback signal; the amplitude limiting circuit is connected with the ultrasonic probe and is used for carrying out amplitude limiting processing on the ultrasonic feedback signal; the passive filter circuit is connected with the amplitude limiting circuit and is used for filtering source-end noise in the ultrasonic feedback signal; the multistage band-pass filter circuit is connected with the passive filter circuit and is used for amplifying and filtering noise of preset frequency on the ultrasonic feedback signal after source-end noise is filtered; the power detection circuit is connected with the multistage band-pass filter circuit and is used for analyzing the ultrasonic feedback signal amplified and subjected to noise filtering by the multistage band-pass filter circuit to obtain an effective detection signal. Wherein the control module comprises a pulse amplification circuit; the control module generates frequency points according to the control instruction; the pulse amplification circuit is used for generating a frequency signal with a frequency corresponding to the ultrasonic probe according to the frequency point. Therefore, the EMI problem in the circuit can be solved by using the method for improving the frequency selection characteristic of the receiving amplification circuit by reducing the pulse amplification factor.
Referring to fig. 2, in an embodiment of the invention, the multistage band-pass filter circuit includes a programmable gain amplifying circuit and a first active band-pass filter circuit; the program control gain amplifying circuit is used for amplifying the ultrasonic feedback signal output by the passive filter circuit; the first active band-pass filter circuit is connected with the program-controlled gain amplifying circuit and is used for carrying out noise filtering processing of preset frequency on the amplified passive filter circuit; furthermore, the device further comprises a second active band-pass filter circuit, wherein the second active band-pass filter circuit is arranged between the control module and the power detection circuit and is used for amplifying the effective detection signal output by the power detection circuit. Therefore, in the embodiment, a plurality of processing circuits are added in the signal processing link; the passive low-pass filter is added at the later stage of the secondary limiting circuit, the source end noise can be well inhibited, after the signal is amplified through an active band-pass, effective signals can be well extracted, meanwhile, the detection circuit has high sensitivity, the small signal detection capability is excellent, the excellent sensitivity of the later stage greatly reduces the voltage peak value output by the pulse amplification circuit, the actually measured peak value is less than 350V, the EMI of the circuit can be reduced, the source end burden of the amplification circuit can be reduced, and the adoption of a low-cost MOS tube is made possible.
Referring to fig. 3 and fig. 4 again, in actual operation, the circuit structure of the passive low-pass filter circuit may refer to fig. 3, and of course, those skilled in the art may make equivalent changes according to actual needs, and the present invention does not limit the circuit structure; based on the passive low-pass filtering circuit provided in fig. 3, the magnitude of the echo signal gain depends on R3, RL, C3, and the larger the RL, the smaller the R3, the larger the C3, and the larger the gain. The larger the contribution to R1 in terms of Vi and VO formula R1 the larger the signal. In an experiment, random noise with unknown reasons exists at the output end of the transformer, so that a plurality of large clutters with unknown reasons are output after the output end of the transformer is subjected to band-pass amplification at a later stage, and the measurement distance is influenced. Therefore, a small capacitor with a small capacitance value (2nf) and a high withstand voltage (2000V) is connected in parallel with the side of R1 to form RC absorption circuit noise. And a circuit for dividing voltage by using a capacitor is arranged at the entrance end of the operational amplifier on the small signal path, and the inductor is added on the signal path to form low pass with the capacitor for the purpose of reducing noise, so that a band pass is formed at the entrance end of the signal. Considering the impedance of the circuit board, 820K is adopted for R1. For excitation large signals see 3.2.2.1, 1000 × 10/1000000 ═ 1/100 ═ 0.01 > 6.36 × 10-5 satisfies the condition. The capacitance actual voltage value w0 is 0.01, w 80K 2 pi 502654, VC 800/√ 1+ (502654/0.01)2 is 1.6 × 10-5, and it is found that the capacitance can be selected to be a small package, and the withstand voltage value does not have to be 0805/25V. Considering the echo small signal, because R1 has no influence on the gain and D4D5 is cut off in the schematic diagram, the newly added C4 and R2 can be combined into a parallel operator, and the gain is also not influenced. The amplitude-frequency characteristic of the circuit basically covers the requirements of 40K to 80K; the experimental result shown in fig. 4 shows that the modification has obvious effect on the optimization of the small signal at a long distance.
In an embodiment of the present invention, the first active band-pass filter circuit and the second active band-pass filter circuit are butterworth band-pass filters; specifically, referring to fig. 5, the band pass filter circuit, i.e., the frequency selective amplifying circuit unit, may be a typical butterworth band pass filter. Wherein, the quality factor is:
Q=1/2*sqrt(2*R17/R13)
magnification:
AW=R17/(R13*2)
is composed ofTherefore, the following steps are carried out:
for f0The frequency-selective amplifying network with fixed frequency, the larger C, the smaller R, the larger the amplifying power, the smaller R, and the smaller R, the lower the input impedance of the circuit. In practical application, three-level Butterworth filtering is adopted, the first-level amplification factor is determined to be 1 time in order to obtain higher input impedance, and the second level is a main amplification path; when the capacitance in the circuit is too small, the resistance is correspondingly increased, and the actual pass frequency point is extremely easy to excessively deviate due to the fact that the resistances connected to the two ends of the operational amplifier are connected in parallel; secondly, the single-path amplification factor of the Butterworth filter circuit is not high actually, the accuracy of the overhigh amplification factor is poor actually, and the 40-time amplification link of the actual circuit is only 20-time amplification factor, so that the last two stages have better 6.6-6.6 links, the input impedance can be improved, and the high amplification factor can be realized.
In the above embodiment, the principle of the pulse amplification circuit can be described with reference to fig. 6, which can use HT7590-7, regulated 9V to power MCP1402, so that VGS of AO4438 does not exceed its allowable voltage by 9V at most. Adding a 1K +102 resistance-capacitance protection MCU pin at the input end of the MC 1402; the output end adopts a 27 omega resistor to protect the G pole of the MOS tube, and the parallel SS24 method is adopted to accelerate the turn-off speed. And 2u capacitor +6.8 omega is used for clamping voltage for the DS end of the frequency point AO4438 of the small probe 80K. The output driving voltage of the circuit designed in this way can be controlled to be not higher than 350V; the high-gain band-pass filter network and the driving circuit are combined to act, so that the EMI performance of the circuit is improved while the performance of the circuit is not reduced.
Due to the fact that the conditions of change of sound wave transmission speed, frequency center point drift, echo signal deformity and the like are caused by the severe environment factors such as humidity and high temperature of the environment in the inspection well, the final measurement result is deviated, and the accuracy does not reach the standard; based on the above situation, in an embodiment of the present invention, a compensation circuit is further added, where the compensation circuit is connected to the control module and is used to compensate for a predetermined rule of the valid detection signal; the control module calculates to obtain a measurement result according to the compensated effective detection signal; wherein the compensation circuit comprises a combination of one or more of a sound speed compensation module, a frequency compensation module, and a malformation correction module; the sound velocity compensation module comprises a temperature and humidity sensor and an air pressure sensor, and is used for acquiring temperature data, humidity data and air pressure data of the environment where the special ultrasonic liquid level measurement device for the inspection well is located through the temperature and humidity sensor and the air pressure sensor, and calculating and obtaining sound velocity information of the current environment according to the temperature data, the humidity data and the air pressure data; the frequency compensation module is used for driving the ultrasonic probe by taking the crystal oscillator as a clock source; the deformity correction module is used for detecting a double-peak deformity signal in the effective detection signal through the hysteresis comparator, and when the double-peak deformity signal exists in the effective detection signal, the effective detection signal is corrected through the signal conversion circuit, so that the double-peak deformity in the effective detection signal is eliminated.
In the above described embodiments, the ultrasonic level gauge is a non-contact level gauge controlled by a microprocessor. The ultrasonic wave of the ultrasonic liquid level meter is sent by a probe (a sensor and a transducer), the sound wave is reflected by the surface of an object and then is received and converted into an electric signal by the same probe, and the distance from the probe to the measured liquid level is calculated according to the transmission time from the emission to the reception of the sound wave. The relationship between the distance value S and the sound velocity C and the transit time T can be formulated as: and S is CxT/2. The significance of the temperature compensation of the ultrasonic liquid level meter is as follows: under atmospheric pressure, the propagation velocity of ultrasonic waves in the air at normal temperature is about 340m/s, and an ultrasonic liquid level meter is adopted for liquid level measurement on the premise of the principle that the propagation velocity C of the ultrasonic waves in a certain medium is a certain value. In practice, the speed of sound varies by about 0.6m/s for every 1 ℃ rise in air temperature. Therefore, if the speed of sound is calculated as a fixed value, the measurement error of the liquid level may be large. In order to meet the requirement of precision in industrial application, the sound velocity must be corrected, and the method for correcting the sound velocity mainly adopts a temperature compensation method. The sound velocity correction by using temperature compensation is to calculate the actual sound velocity according to the approximate relation C of the temperature and the sound velocity, namely 331.45+ 0.607T (DEG C) or C, 20.607T 1/2, so as to achieve the purpose of compensating the sound velocity. The specific implementation mode is that a temperature sensor is added in the probe to measure the temperature change of the environment. When the ultrasonic liquid level meter works, the ambient temperature value at that time is converted into a digital signal and transmitted to the single chip microcomputer, and then the actual sound velocity at the temperature is calculated by the single chip microcomputer.
In the above embodiment, the malformation correcting module can refer to fig. 11A in actual operation, and may include five parts, i.e., threshold detection, signal input, signal malformation, signal conversion, and software processing as a whole, and its circuit structure may refer to fig. 11B; in this embodiment, the threshold detection part circuit mainly functions to detect whether the input signal is valid, remove noise interference, and output a high level when the input signal WAVE _ SIGN is greater than Vref _ ON, so as to notify the subsequent circuits to process the signal. The circuit implementation is as shown in the circuit diagram part AR1, and the comparator is formed by adopting an operational amplifier, and the transmission characteristic is as shown in the following FIG. 11C; the signal input control function is to transmit a signal to a post-stage processing circuit when an ultrasonic signal is effective, and is realized by adopting a single-pole double-throw analog switch, the control signal is an output signal of a threshold detection circuit, the analog switch is made into an integrated circuit similar to the single-pole double-throw switch function by adopting a field effect tube, after the control end is gated, the selected end is in a low-resistance state to the output end, and the other end is in a high-resistance state, so that the signal switching function is realized, and the specific reference can be made to fig. 11D; the function of the malformation detecting circuit is that when the malformation signal shown in fig. 9B is input, the output signal does not continue to be at a high level after the first peak signal is met, and the output signal is switched to be at a low level after the second peak signal is ended, thereby realizing the correction processing of the double-peak malformation signal; the core component of the circuit is a hysteresis comparator, and the transmission characteristic is shown in fig. 11E; the signal conversion road function is to convert the high and low level signals processed by the malformed signal processing circuit into triangular wave signals, and the peak point of the converted signals is the central point of the ultrasonic echo, so that the measured distance can be calculated; the software realizes window detection through the ADC, triggers the malformation correction function when two peaks are detected in the window and the malformation correction circuit has only one waveform, and the signal source for calculating the distance is taken from the signal source of the malformation correction circuit part, so that the purpose of malformation correction is achieved, and the measurement accuracy is improved.
Specifically, referring to fig. 7, regarding the implementation principle of the sound velocity compensation module, the transducer sends a transient sound wave, the sound wave encounters an obstacle and reflects the sound wave, the total time from sending the ultrasonic wave to receiving the echo is T (T1+ T2), and assuming that the sound velocity is a fixed value V, the distance from the transducer to the obstacle is:
L=V×(T/2)
as can be seen from the above equation, the speed of sound will affect the measurement result. In practice, the speed of sound V is not a constant value, and its value will vary depending on various factors such as the temperature, humidity, pressure, and gas composition of the air. The temperature and the humidity of air in the inspection well are changed most frequently than the common environment, and as the equipment is generally applied to coastal cities, the air pressure change of the coastal cities is severe, the temperature is from-30 ℃ to 60 ℃, and the humidity is from 20% RH to 100% RH, which are common conditions, the three parameters greatly influence the measurement accuracy, and the relationship formula of the three parameters and the sound velocity is as follows:
pw is the partial pressure of water vapor in the air (Pw is the saturated vapor pressure of water relative humidity), T is the temperature, and P is the atmospheric pressure.
The sound velocity compensation part comprises a high-precision temperature and humidity sensor and an air pressure sensor, and the actual sound velocity is calculated in the control core through the three parameters so as to solve the measurement distance.
The research shows that the measuring range of the ultrasonic level meter can not reach the nominal value in the process of measuring the liquid level of the inspection well, most of the ultrasonic level meters adopt an RC oscillator as a clock source to drive the transducer, the error of the RC oscillator in a wide temperature range is up to +/-10%, the allowed frequency error of the ultrasonic transducer is generally less than 5% due to the mechanical structure of the ultrasonic transducer, and the transmitting power and the receiving power of ultrasonic waves can be greatly reduced when the range is exceeded, so that the full-scale use can not be realized. In addition, due to deviation from the central frequency point, the loss of electric signals can be caused in an echo processing circuit, and the measuring range is further reduced; in order to solve the problem, the frequency compensation module provided by the invention mainly replaces an oscillation source with a crystal oscillator and assists a temperature compensation technology, wherein a frequency error is shown in the following figure 8, a shadow part is a final frequency error, and the frequency error can be reduced to twenty parts per million under the condition that the crystal oscillator is adopted as a clock source and sound velocity compensation is added.
Referring to fig. 9A to 9G, most of the measured liquid level is a fluctuating liquid level, and in addition, the obstacle in the manhole is more and the space is closed, so that the ultrasonic wave in the manhole is reflected for many times, the false echo is serious, and serious problems such as incapability of measuring or wrong measured value are often caused; therefore, the present invention further provides a malformation correcting module, specifically referring to fig. 9A, where the normal echo has only one pulse; after compensation correction is performed by the compensation method provided by the present invention, as shown in fig. 9B, the waveform of the effective detection signal is detected by an analog/digital converter and a malformation correction circuit, and when the analog/digital converter detects that two peaks exist in a predetermined period of the effective detection signal and the detection result of the malformation correction circuit is a peak, the measurement result is calculated by the detection result of the malformation correction circuit; the waveform then changes to that shown in fig. 9C, and the echo center point can be calculated normally. Based on the principle, please refer to the multiple echo correction flow charts shown in fig. 9D to 9G, the echo is abnormal in a static state due to interference of other obstacles in the inspection well, and the normal static echo is almost 0; firstly, measuring an echo (a first peak value is a measuring point), and then, subtracting the abnormal echo by adopting the compensation algorithm to obtain a correct echo: therefore, the waveform distortion in the inspection well can be corrected through the medium compensation algorithm.
Referring to fig. 10, the present invention further provides a method for measuring an inspection well-dedicated ultrasonic liquid level, the method comprising: generating a frequency signal with a frequency corresponding to the ultrasonic probe according to the control instruction; transmitting ultrasonic detection signals with corresponding frequencies to a detected area according to the frequency signals, and receiving feedback ultrasonic feedback signals; carrying out amplitude limiting processing on the ultrasonic feedback signal, and filtering source-end noise in the ultrasonic feedback signal; amplifying and filtering the ultrasonic feedback signal with the source end noise filtered, and analyzing to obtain an effective detection signal; and calculating according to the effective detection signal to obtain a measurement result.
In the above embodiment, the obtaining of the measurement result by calculating from the valid detection signal includes: collecting temperature data, humidity data and air pressure data of the environment where the ultrasonic liquid level measuring device special for the inspection well is located; calculating to obtain sound velocity information of the current environment according to the temperature data, the humidity data and the air pressure data; and compensating the effective detection signal according to the sound velocity information, and calculating according to the compensated effective detection signal to obtain a measurement result.
In the above method for measuring the liquid level of the ultrasonic wave specially used for the inspection well, preferably, the obtaining of the measurement result by calculating according to the effective detection signal includes:
the invention has the beneficial technical effects that: a high-sensitivity echo processing system is formed by a passive filter, a multistage band-pass filter and a logarithmic detection technology, so that partial voltage of a pulse amplification circuit is reduced, and the EMI problem is solved; the compensation circuit is utilized to obviously improve the measurement precision of the liquid level in the inspection well, realize full-scale measurement so as to adapt to the complex environment in the inspection well, restore correct echo signals and achieve the function of accurately measuring the liquid level of the inspection well.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. An ultrasonic liquid level measuring device special for an inspection well is characterized by comprising a control module, an ultrasonic probe, an amplitude limiting circuit, a passive filter circuit, a multistage band-pass filter circuit and a power detection circuit;
the control module is used for generating a frequency signal with a frequency corresponding to the ultrasonic probe according to a control instruction; and calculating to obtain a measurement result according to the effective detection signal;
the ultrasonic probe is used for transmitting an ultrasonic detection signal with corresponding frequency to a detected area according to the frequency signal and receiving a feedback ultrasonic feedback signal;
the amplitude limiting circuit is connected with the ultrasonic probe and is used for carrying out amplitude limiting processing on the ultrasonic feedback signal;
the passive filter circuit is connected with the amplitude limiting circuit and is used for filtering source end noise randomly generated at the output end of the transformer in the ultrasonic feedback signal;
the multistage band-pass filter circuit is connected with the passive filter circuit and is used for amplifying and filtering noise of preset frequency on the ultrasonic feedback signal after source-end noise is filtered;
the power detection circuit is connected with the multistage band-pass filter circuit and is used for analyzing the ultrasonic feedback signal amplified and subjected to noise filtering by the multistage band-pass filter circuit to obtain an effective detection signal;
the multistage band-pass filter circuit comprises a program-controlled gain amplification circuit and a first active band-pass filter circuit; the program control gain amplifying circuit is used for amplifying the ultrasonic feedback signal output by the passive filter circuit; the first active band-pass filter circuit is connected with the program-controlled gain amplifying circuit and is used for carrying out noise filtering processing of preset frequency on the amplified passive filter circuit.
2. The inspection well special-purpose ultrasonic liquid level measuring device according to claim 1, wherein the control module comprises a pulse amplification circuit; the control module generates frequency points according to the control instruction; the pulse amplification circuit is used for generating a frequency signal with a frequency corresponding to the ultrasonic probe according to the frequency point.
3. The special ultrasonic liquid level measuring device for the inspection well according to claim 1, further comprising a second active band-pass filter circuit, wherein the second active band-pass filter circuit is arranged between the control module and the power detection circuit and is used for amplifying effective detection signals output by the power detection circuit.
4. The inspection well dedicated ultrasonic liquid level measurement device according to claim 3, wherein the first active band-pass filter circuit and the second active band-pass filter circuit are Butterworth band-pass filters.
5. The inspection well-dedicated ultrasonic liquid level measurement device according to claim 1, further comprising a compensation circuit connected to the control module for compensating for a predetermined rule of the effective detection signal; and the control module calculates to obtain a measurement result according to the compensated effective detection signal.
6. The inspection well-dedicated ultrasonic liquid level measurement device according to claim 5, wherein the compensation circuit comprises a combination of one or more of a sound speed compensation module, a frequency compensation module and a malformation correction module;
the sound velocity compensation module comprises a temperature and humidity sensor and an air pressure sensor, and is used for acquiring temperature data, humidity data and air pressure data of the environment where the special ultrasonic liquid level measurement device for the inspection well is located through the temperature and humidity sensor and the air pressure sensor, and calculating and obtaining sound velocity information of the current environment according to the temperature data, the humidity data and the air pressure data;
the frequency compensation module is used for driving the ultrasonic probe by taking the crystal oscillator as a clock source;
the deformity correction module is used for detecting a double-peak deformity signal in the effective detection signal through the hysteresis comparator, and when the double-peak deformity signal exists in the effective detection signal, the effective detection signal is corrected through the signal conversion circuit, so that the double-peak deformity in the effective detection signal is eliminated.
7. An ultrasonic liquid level measurement method special for an inspection well is characterized by comprising the following steps:
generating a frequency signal with a frequency corresponding to the ultrasonic probe according to the control instruction;
transmitting ultrasonic detection signals with corresponding frequencies to a detected area according to the frequency signals, and receiving feedback ultrasonic feedback signals;
carrying out amplitude limiting processing on the ultrasonic feedback signal, and filtering source end noise randomly generated by the output end of the transformer in the ultrasonic feedback signal;
amplifying and filtering the ultrasonic feedback signal with the source end noise filtered, and analyzing to obtain an effective detection signal;
calculating according to the effective detection signal to obtain a measurement result;
the amplifying and noise-filtering processing of the preset frequency on the ultrasonic feedback signal after the source-end noise is filtered comprises the following steps: amplifying the ultrasonic feedback signal; and carrying out noise filtering processing of preset frequency on the amplified ultrasonic feedback signal through a passive filter circuit.
8. The inspection well-dedicated ultrasonic liquid level measurement method according to claim 7, wherein obtaining the measurement result by calculation based on the effective detection signal comprises:
collecting temperature data, humidity data and air pressure data of the environment where the ultrasonic liquid level measuring device special for the inspection well is located;
calculating to obtain sound velocity information of the current environment according to the temperature data, the humidity data and the air pressure data;
and compensating the effective detection signal according to the sound velocity information, and calculating according to the compensated effective detection signal to obtain a measurement result.
9. The inspection well-dedicated ultrasonic liquid level measurement method according to claim 7, wherein obtaining the measurement result by calculation based on the effective detection signal comprises: the waveform of the effective detection signal is detected through an analog-to-digital converter and a malformation correction circuit respectively, and when the analog-to-digital converter detects that two peak values exist in a preset period of the effective detection signal and the detection result of the malformation correction circuit is one peak value, the measurement result is obtained through the calculation of the detection result of the malformation correction circuit.
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