CN109900333B - Self-adaptive electromagnetic flowmeter and measuring method - Google Patents
Self-adaptive electromagnetic flowmeter and measuring method Download PDFInfo
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- CN109900333B CN109900333B CN201910295645.5A CN201910295645A CN109900333B CN 109900333 B CN109900333 B CN 109900333B CN 201910295645 A CN201910295645 A CN 201910295645A CN 109900333 B CN109900333 B CN 109900333B
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Abstract
The invention discloses a self-adaptive novel electromagnetic flowmeter and a measuring method, comprising a fluid property sensor group, a signal processing circuit, a microprocessor, a D/A excitation signal generator, a data processing module and an LCD display screen. The fluid property sensor group detects fluid related information and outputs an electric signal to be sent to the signal processing circuit, the signal processing circuit is connected with the microprocessor after filtering and amplifying to obtain an undistorted signal, the fluid information is provided through analysis, and the adopted measuring mode is determined according to the transmitted fluid information: when the fluid is normal, a matched excitation generation program is called; when the fluid is unconventional, the microprocessor sends out a plurality of preset frequencies as sweep frequency signals and adds the sweep frequency signals to the D/A excitation signal generator, the D/A excitation signal generator generates excitation waves with different shapes or excitation waves with a plurality of frequencies, and the microprocessor analyzes signals transmitted by the signal processing circuit and is connected with the LCD for displaying, so that the measurement precision of the electromagnetic flowmeter is improved, and the accurate measurement is realized.
Description
Technical Field
The invention relates to the technical field of electromagnetic flow meters, in particular to an electromagnetic flow meter capable of automatically selecting an excitation mode according to different fluids in a pipeline.
Background
One purpose of the flow meter measurement is to provide an accurate value of the flow parameter to a manager or control system during the production process, so as to make reasonable judgment and adjustment, achieve excellent control, and improve the quality and yield of the product. The electromagnetic flowmeter is used as a meter for measuring the volume flow of the conductive liquid according to Faraday electromagnetic induction law, and the excitation technology determines the characteristics of the working magnetic field of the electromagnetic flow sensor, so that the excitation technology affects the detection precision of the electromagnetic flowmeter. With the development of the electromagnetic flowmeter, the excitation technology also goes through five stages of direct current excitation, power frequency sine wave excitation, low-frequency rectangular wave excitation, low-frequency three-value rectangular wave excitation and double-frequency rectangular wave excitation. However, these excitation techniques have drawbacks, such as electrode polarization effect caused by dc excitation, and orthogonal interference effect caused by power frequency sine wave excitation. The differential interference and the in-phase interference introduced by the low-frequency rectangular wave excitation technology which are most commonly used at present obviously reduce the signal-to-noise ratio of the sensor output signal induction in a low flow velocity stage, so that the measurement error is extremely large.
In modern industry, flow measurement is an indispensable link in industrial production, and flow is one of five measurement parameters. The accurate measurement is very helpful for production guidance and planning. The current-stage flowmeter in China is a common flowmeter, and a rectangular wave excitation technology is adopted. In the existing excitation mode at the present stage, the problems of low measurement precision, poor zero point stability, large differential interference and homodromous interference and the like are solved step by step, but the single excitation mode is difficult to meet the requirements of measuring different fluid flow rates. For example, when solid particles such as slurry and pulp and low-conductivity fluid are measured in an electromagnetic flowmeter using three-value low-frequency rectangular wave excitation, electrical noise is generated, which makes an output signal extremely unstable. This problem can be effectively solved if double-frequency rectangular wave excitation is adopted.
The Chinese patent discloses a constant current control system of a frequency conversion electromagnetic flowmeter exciting coil (Li, chen Jie, hu Jinyin, etc. the constant current control system of the frequency conversion electromagnetic flowmeter exciting coil, application number: 201610360618.8, application date: 2016.05.28) based on a constant current control system, which consists of a direct current power supply, a constant current control circuit, a current detection circuit, a power supply change-over switch A and a current change-over switch B. The direct current power supply supplies power to the exciting coil, and exciting current flows to the reference ground through the exciting coil and the constant current control circuit. The power supply changeover switch A combines with the current changeover switch B to generate a changeover control signal of a high-voltage power supply and a low-voltage power supply in the direct-current power supply; when the excitation frequency of the variable-frequency electromagnetic flowmeter is low, the current change-over switch II is always closed, and the excitation power supply of the excitation coil is a low-voltage power supply; when the exciting frequency of the variable-frequency electromagnetic flowmeter is high and the exciting current does not reach a preset value, the high-voltage power supply is used as an exciting working power supply, and after the exciting current reaches the preset value, the high-voltage power supply is turned off, and the power is supplied by the low-voltage power supply. The system is applied to slurry fluid measurement, and can ensure the zero point stability and strong noise resistance, and ensure that the heat consumption of the device is small. However, this system has the following drawbacks: when fluids with different properties flow in the pipeline of the electromagnetic flowmeter, a single excitation generating device in the system cannot meet measurement requirements under different conditions, and the patent is not suitable for electromagnetic flowmeters for measuring flow rates of various fluids.
Aiming at the defects existing in the prior art, the invention provides an application which can adapt to the measurement of the electromagnetic flowmeter under different fluids.
Disclosure of Invention
The invention aims at solving the technical problems that the application range of the existing excitation mode, namely the DC excitation mode, is limited by the polarization potential barrier on the electrode, so that the DC excitation mode with a certain value is only suitable for measuring non-electrolyte (such as liquid metal) liquid; the power frequency sine wave excitation is easy to cause zero point variation, so that the measurement accuracy is reduced. The method does not generate peak noise generated when solids wipe the surface of the electrode, and is applied to measuring liquid-solid two-phase flow such as slurry, ore pulp and the like; the non-sinusoidal ac excitation need not be calculated to remove variations in the magnetic field strength; the low-frequency rectangular wave excitation reduces the excitation frequency, the zero point stability can be improved, but the instrument has low-frequency interference resistance, the response speed is low, if the excitation frequency is high, the low-frequency interference resistance is improved, but the zero point stability of the electromagnetic flowmeter is reduced. The peak potential interference can be generated when the liquid-solid two-phase conductive fluid such as slurry is measured, and the method is not suitable for measuring the liquid-solid two-phase conductive fluid such as slurry; the three-value low-frequency rectangular wave excitation adopts excitation current with sine law change, has better zero point stability, solves the influence of interference potential, reduces response speed and has electric noise; the double-frequency rectangular wave excitation has the advantages of excellent zero point stability of the low-frequency rectangular wave excitation technology and strong inhibition capability of the high-frequency rectangular wave excitation technology on fluid noise. The method can be used for measuring solid-liquid two-phase conductive fluid and low-conductivity fluid such as slurry, paper pulp, ore pulp and the like. In summary, the single excitation method cannot meet the flow rate measurement requirement when multiple different fluids in the pipeline pass through. Therefore, the electromagnetic flowmeter can correspondingly select different excitation modes according to different fluid characteristics so as to achieve the aim of matching the optimal excitation modes with different fluids and improving the measurement accuracy.
To achieve the above object, the present invention is conceived as follows: the electromagnetic flowmeter determines the property of the fluid in the pipeline according to the conductivity, the solid particle content and the viscosity of the fluid detected by the fluid property sensor group, and the microprocessor selects the excitation mode which is most matched with the fluid. If the detected fluid is very special and is not matched with the set excitation mode, the frequency sweep signal is adopted to carry out multi-frequency scanning, and the data after frequency sweep is processed to realize self-adaptability.
According to the inventive concept, the invention adopts the following technical scheme: the self-adaptive electromagnetic flowmeter comprises a fluid property sensor group, a signal processing circuit, a microprocessor, a D/A excitation signal generator, a sweep frequency circuit, a data processing module and an LCD display screen. The method is characterized in that the fluid property sensor group is connected with the signal processing circuit, the signal processing circuit analyzes and processes output signals of the fluid property sensor group to select odd harmonics which are less interfered by slurry noise to reflect flow signals, the flow signals are analyzed to obtain fluid properties which are matched with address codes of fluid to be measured in the measuring device, the fluid properties are connected with the D/A excitation signal generator through the microprocessor, the address codes provided by the signal processing circuit are matched with waveforms in the D/A excitation signal generator to obtain an excitation mode which is most matched with the fluid, when the fluid to be measured is extremely special, the measuring device can not be matched with various conventional excitation modes designed, the measuring device can measure the fluid through a sweep frequency mode, wherein the microprocessor provides sweep signals required by the sweep signals for the sweep circuit, the sweep signals generated by the microprocessor are added to the D/A excitation signal generator, voltage signals under different frequencies are obtained through measurement by using magnetic waves with different frequencies, the data processing module obtains a multi-frequency relation between the fluid obtained through analysis and the voltage signals obtained through final conversion when the conventional fluid is deduced, the fluid is used as a multi-frequency signal, the optimal flow rate stability is obtained, the data is displayed on the LCD signal display of the fluid is displayed at the same frequency, and the optimal frequency stability is obtained, and the optimal flow rate is displayed after the data is processed, and the data is displayed.
The fluid property sensor group consists of a fluid conductivity sensor, a fluid particulate matter content sensor and a fluid viscosity sensor, and is arranged at the forefront end of the electromagnetic flowmeter for measuring fluid properties, when fluid in the pipeline passes through the sensor group, the fluid property sensor group can detect the fluid properties in a first time, and the fluid property sensor group is mainly used for detecting fluid properties in the pipeline, namely fluid conductivity, solid particulate matter content and fluid viscosity parameters; according to different fluids flowing in the pipeline, when the detected fluid is non-electrolyte liquid (such as liquid metal), the measuring device automatically adopts a direct current excitation mode to measure; when the detected fluid is a liquid-solid two-phase flow such as slurry, ore pulp and the like, the measuring device automatically adopts a power frequency sine wave excitation mode to measure; when the detected fluid is a fluid containing solid particles, fiber and the like, such as paper pulp and the like, and low-conductivity fluid, the measuring device automatically adopts a double-frequency rectangular wave excitation mode to measure; when the fluid detected by the fluid property sensor group is extremely special and cannot be matched with the preset fluid of the measuring device, the fluid property sensor group transmits the detected fluid information to the microprocessor through the signal processing circuit, and the measuring device automatically performs flow rate measurement in a sweep frequency mode. The method is mainly used for detecting the properties of the fluid in the pipeline, including the fluid conductivity, the solid particle content and the fluid viscosity. The related information of the detected fluid is accurately output through the fluid property sensor group, so that the electromagnetic flowmeter can accurately detect the fluid information of different fluids when the fluids flow through the pipeline.
The signal processing circuit is composed of a high-pass filter circuit, a low-pass filter circuit and an amplifying circuit, the signal processing circuit receives the output signal of the fluid property sensor group, filters tiny direct current components mixed in the signal through the high-pass filter circuit, filters high-frequency peak interference through the low-pass filter circuit, and finally amplifies the signal after the signal is filtered by the amplifying circuit so as to achieve the purposes of ensuring the signal fidelity and facilitating the analysis and processing; the signal processing circuit is used for filtering tiny direct current components and high-frequency peak interference mixed in signals through a series of reasonable and effective circuit processing, and finally the amplifying circuit is used for amplifying the signals after the filtering circuit so as to achieve the purposes of ensuring the signal fidelity and facilitating the analysis and the processing. It is further determined whether the type of fluid detected matches an address code set by the measuring device.
The microprocessor is used for receiving the address code transmitted by the signal processing circuit, matching the received address code with the internal programming program of the microprocessor to achieve the purpose of adaptively selecting the most suitable excitation mode design program so as to control the D/A excitation signal generator to output the optimal excitation waveform suitable for the D/A excitation signal generator, when the received address code cannot be matched with the existing design program, the electromagnetic flowmeter system automatically selects the sweep mode to perform flow rate measurement, the microprocessor generates the required sweep signal by programming to provide an input signal for the sweep circuit, and the microprocessor is used for controlling the D/A excitation signal generator to have the program design of automatically controlling and selecting the corresponding excitation waveform circuit according to the address code provided by the structure. When the fluid information transmitted by the signal processing circuit to the microprocessor matches the setting of the measuring device, the measurement is performed with a conventional fluid. The microprocessor selects excitation generation program design matched with the address code according to the received address code so as to realize the function of self-adapting different waveforms by different fluids. In addition, the microprocessor system has the function of generating sweep frequency signals. When the fluid information transmitted by the signal processing circuit to the microprocessor does not correspond to the settings of the measurement system, the measurement is performed with an unconventional fluid. At this point, the microprocessor is programmed to generate the required sweep signal and load the sweep signal into the sweep circuit for testing in the presence of unconventional fluids.
The D/A excitation signal generator is composed of a high-precision digital-to-analog conversion chip and an external circuit, and is provided with five different excitation waveforms, namely direct current excitation, power frequency sine wave excitation, low-frequency rectangular wave excitation, double-frequency rectangular wave excitation and bidirectional trapezoidal wave excitation, so as to be self-adaptive to different excitation modes required by different fluids flowing through pipelines. The D/A excitation signal generator is also provided with a rectangular wave excitation mode for outputting different frequencies when unconventional fluid flows through a pipeline to measure the flow rate of the unconventional fluid, the D/A excitation signal generator receives an excitation programming program transmitted by a microprocessor, processes the excitation wave through a high-precision digital-to-analog conversion chip to generate a required excitation wave, and loads the generated excitation wave on a coil of the electromagnetic flowmeter to measure the flow rate, so that the electromagnetic flowmeter can measure the flow rate in different fluid environments by using the best matched excitation mode. The signal generator receives the instruction of the microprocessor and generates different excitation waveforms to be applied to the excitation coil under different instruction requirements, so that the electromagnetic flowmeter can measure by using the best matched excitation mode under the application of different fluid measurement.
The frequency sweep circuit takes a microprocessor as a core, and the frequency sweep circuit is controlled by the microprocessor to generate frequency sweep signals and consists of the microprocessor, a direct digital frequency synthesizer, a low-pass filter, rectifying and filtering and an AD conversion circuit. After receiving the address code transmitted by the signal processing circuit, the microprocessor starts corresponding programming, and after starting to input the initial frequency, the ending frequency and the frequency interval, the AD conversion circuit synthesizes corresponding frequencies to obtain sweep frequency signals with different frequencies required by the measuring device. According to different flow rates and fluid properties, the microprocessor generates different sweep frequency signal frequency ranges and time intervals, and loads the sweep frequency signal frequency ranges and time intervals to the D/A excitation signal generator, and when special fluid exists in a pipeline and the existing excitation mode of the system cannot meet the measurement requirement, the sweep frequency circuit is used for measuring the flow rate. The frequency sweep circuit carries out frequency sweep processing on the three-value rectangular wave excitation, when the flow speed is faster, the frequency sweep frequency range is larger, the frequency step length is 0.2Hz from 6.25Hz to 2KHz, and the time interval between different frequencies is 0.1s; when the fluid flow speed is slower, the frequency sweep frequency range is smaller, the frequency sweep signal is 6.25Hz to 1KHz, the step length is 0.25Hz, the time interval between different frequencies is 0.2s, the frequency sweep signal generated by the frequency sweep circuit is used for obtaining the excitation waveforms under different frequencies and loading the excitation waveforms in the excitation coil, the multi-frequency excitation waveform measurement is carried out to obtain related data, the related data are transmitted to the data processing module, the voltage signals under the measurement of a plurality of groups of excitation waves with different frequencies are obtained, and the excitation frequency data with the minimum interference are selected as the final result through data comparison.
The data processing module carries out excitation sampling on an excitation unit of the electromagnetic flowmeter to obtain analog signals of excitation current and voltage during conventional fluid measurement, corresponding digital signals are obtained after analog-to-digital conversion, the fluid flow rate in the sampling period is calculated according to the excitation current and the voltage of the digital signals in the same sampling period after conversion, the data processing circuit carries out analysis and comparison on voltage signals under multiple groups of excitation frequencies during non-conventional fluid measurement to select the highest signal-to-noise ratio, the waveform has the smallest change along with time, namely the best stability, the excitation frequency corresponding to the most concentrated power spectrum is used as the excitation mode of the special fluid, and then the excitation current and the voltage under the frequency are used as analog signals of the data processing module, and the fluid flow rate is obtained by adopting the data processing method which is the same as that of the conventional fluid.
A method of measuring an adaptive electromagnetic flowmeter, comprising the steps of:
step1, when fluid passes through a pipeline, firstly detecting the property of the fluid by a fluid property sensor group, then carrying out filtering amplification processing on the obtained fluid signal by a high-pass filtering circuit, a low-pass filtering circuit and an amplifying circuit in a signal processing circuit to obtain fluid information which is matched with an address code arranged in the device, and then carrying out control identification on the address code by a microprocessor;
the step2.D/A excitation signal generator receives the program adopted by the microprocessor to generate excitation signals, the generated excitation signals are loaded on the excitation coil to measure the flow velocity, the obtained data are analyzed and processed by the data processing module, and the final result is displayed by the LCD display screen.
When the signal processing circuit transmits the acquired signal to the microprocessor, the measuring device performs the process of matching the set address code on the fluid, the microprocessor selectively calls an excitation generation program suitable for the received fluid information and transmits the excitation generation program to the D/A excitation signal generator only when the received fluid information is matched with the set address code, and when the received fluid information is not matched with the set content, the measuring device automatically generates a sweep frequency signal, loads the sweep frequency signal to the sweep frequency circuit and cooperates with the D/A excitation signal generator to generate a multi-frequency excitation signal for measurement.
The system of the invention comprises: the device comprises a fluid property sensor group, a signal processing circuit, a microprocessor, a D/A excitation signal generator, a sweep frequency circuit, a data processing module and an LCD display screen, and is shown in figure 2.
The D/A excitation signal generator part is shown in FIG. 3
The working process of the invention is as follows: when fluid passes through the pipeline, the fluid property sensor group part firstly detects the fluid property, the frequency spectrum characteristic of the output signal detected by the sensor, and the odd harmonic amplitude which is least interfered by the fluid noise is selected to reflect the magnitude of the flow signal, so that the measuring device can accurately extract the flow information from the output signal by avoiding the noise interference. And analyzing the obtained basic information of the detected fluid, comparing and analyzing the basic information with the fluid parameter designed by the measuring device to obtain the fluid address code required by the measuring device at the moment, and judging whether the existing excitation mode can meet the measurement requirement according to the address code obtained by the detection result. If yes, the microprocessor controls and selects an excitation mode program matched with the excitation mode program, and the D/A excitation signal generator generates corresponding waveforms to load the waveforms on the excitation coil for fluid flow rate measurement; if the measured fluid is unable to achieve the purpose of accurately measuring the flow rate by the special existing excitation mode, generating a sweep frequency signal by the microprocessor, carrying out multi-frequency scanning on the three-value rectangular wave through the sweep frequency circuit to obtain a plurality of groups of data, and carrying out flow rate measurement by taking the excitation frequency corresponding to the optimal data as the excitation mode of the special fluid through data comparison analysis.
Compared with the prior art, the invention has the following obvious outstanding characteristics and obvious technical progress: the self-adaptive electromagnetic flowmeter can perform excitation mode change according to different fluid properties in the pipeline, so that the accuracy and precision of fluid flow velocity measurement are ensured. In addition, for the special fluid which cannot be accurately measured by the existing excitation technology, the optimal excitation mode under the special fluid is obtained by adopting a frequency sweep signal through a multi-frequency scanning method, so that the aim of accurate measurement is fulfilled.
Drawings
FIG. 1 is a block diagram of an adaptive electromagnetic flowmeter
FIG. 2 is a block flow diagram of an adaptive electromagnetic flowmeter
FIG. 3 is an overall block diagram of a new measurement system for an adaptive electromagnetic flowmeter
FIG. 4 is a block diagram of a D/A excitation signal generator
FIG. 5 is a block diagram of a sweep frequency circuit structure
Detailed Description
The invention will be further described with reference to the accompanying drawings
Embodiment one:
referring to fig. 1-4, the adaptive electromagnetic flowmeter system comprises a fluid property sensor group 1, a signal processing circuit 2, a microprocessor 3, a D/a excitation signal generator 4, a sweep frequency circuit 5, a data processing module 6 and an LCD display screen 7, and is characterized in that: the fluid property sensor group 1 is connected with the signal processing circuit 2, the signal processing circuit 2 analyzes and processes the output signal of the fluid property sensor group to obtain the fluid property as the address code of the system, the address code provided by the signal processing circuit 2 is connected with the D/A excitation signal generator 4 through the microprocessor 3, and the address code is matched with the waveform in the D/A excitation signal generator 4 to obtain the most suitable excitation mode for the fluid. The microprocessor 3 also provides the sweep frequency signal required by the sweep frequency circuit 5, the generated sweep frequency signal is added to the D/a excitation signal generator 4, the excitation waves with different frequencies are used for measurement to obtain voltage signals with different frequencies, and finally the optimal result is obtained through analysis and comparison by the data processing module 6 and then is reflected on the LCD display screen 7.
Embodiment two:
the second embodiment is basically the same as the first embodiment, and is specifically as follows:
the fluid property sensor group 1 is composed of a fluid conductivity sensor, a fluid particulate matter content sensor and a fluid viscosity sensor, and is mainly used for detecting fluid properties in a pipeline, including fluid conductivity, solid particulate matter content, fluid viscosity and the like. The related information of the detected fluid is accurately output through the fluid property sensor group 1. The signal processing circuit 2 is composed of a high-pass filter circuit, a low-pass filter circuit and an amplifying circuit, and judges the type of the detected fluid and the serial number set by the system through processing the signals output by the fluid property sensor group 1, namely the serial number is used as an address code processed by the microprocessor 3 to be matched.
The microprocessor 3 is used for controlling the D/a excitation signal generator 4, and has a program design for automatically controlling and selecting a corresponding excitation waveform circuit according to the address code provided by the structure, so as to realize the function of self-adapting different waveforms by different fluids. In addition, the microprocessor 3 system has the function of generating a frequency sweep signal, and the generated frequency sweep signal is loaded on the frequency sweep circuit 5 for testing under the condition of special fluid under the control of a microprocessor program.
The D/A excitation signal generator 4 is composed of a high-precision digital-to-analog conversion chip and an external circuit, and the D/A excitation signal generator 4 receives the instruction of the microprocessor 3 and generates different excitation waveforms under different instruction requirements and applies the different excitation waveforms to the excitation coil so that the electromagnetic flowmeter can measure by using the most matched excitation modes under the application of different fluid measurement.
The sweep frequency circuit 5 is controlled by the microprocessor 3 to generate sweep frequency signals, when special fluid exists in a pipeline and the existing excitation mode of the system cannot meet the measurement requirement, the sweep frequency circuit 5 is adopted to conduct sweep frequency treatment on three-value rectangular wave excitation, voltage signals under the measurement of multiple groups of excitation waves with different frequencies are obtained, and excitation frequency data with the smallest interference are selected as a final result through data comparison.
Claims (9)
1. An adaptive electromagnetic flowmeter comprises a fluid property sensor group (1), a signal processing circuit (2), a microprocessor (3), a D/A excitation signal generator (4), a sweep frequency circuit (5), a data processing module (6) and an LCD display screen (7), and is characterized in that the fluid property sensor group (1) is connected with the signal processing circuit (2), the signal processing circuit (2) analyzes and processes output signals of the fluid property sensor group (1) to select odd harmonics which are less interfered by slurry noise to reflect flow signals, the flow signals are analyzed to obtain the fluid property which is matched with an address code set in the electromagnetic flowmeter at the moment, the address code provided by the microprocessor (3) is connected with the D/A excitation signal generator (4), the address code provided by the signal processing circuit (2) is matched with waveforms in the D/A excitation signal generator (4) to obtain an excitation mode which is matched with the fluid best, when the measured fluid is very special, a plurality of conventional excitation modes designed in the electromagnetic flowmeter cannot be matched, the electromagnetic flowmeter measures through the mode, the microprocessor (3) provides the address code for the microprocessor (5) to provide the address code, the address code is different from the frequency of the frequency generator (4) to generate an excitation signal with different frequency of the frequency generator (4) when the frequency of the frequency generator is different from the frequency generator, the data processing module (6) analyzes and deduces the relation between the voltage signal obtained by final conversion and the flow velocity to obtain the flow velocity of the fluid at the moment when the fluid is normal, selects the voltage signal at the multiple frequencies by taking the signal-to-noise ratio, the stability and the power spectrum as selection criteria when the fluid is abnormal to obtain the voltage signal at the optimal frequency, then analyzes and processes corresponding data with the conventional fluid processing steps to obtain the flow velocity of the fluid, and finally the data result is reflected on the LCD display screen (7).
2. An adaptive electromagnetic flowmeter according to claim 1, characterized in that the fluid property sensor set (1) comprises a fluid conductivity sensor (8), a fluid particulate content sensor (9) and a fluid viscosity sensor (10), all mounted at the foremost end of the electromagnetic flowmeter for fluid property measurement, and being capable of detecting fluid properties in a first time when there is fluid in the pipeline, the fluid property sensor set (1) being adapted to detect fluid properties in the pipeline, namely fluid conductivity, solid particulate content and fluid viscosity parameters; according to different fluids flowing in the pipeline, when the detected fluid is non-electrolyte liquid, the electromagnetic flowmeter automatically adopts a direct current excitation mode to measure; when the detected fluid is a liquid-solid two-phase flow, the electromagnetic flowmeter automatically adopts a power frequency sine wave excitation mode to measure; when the detected fluid is a fluid containing solid particles and fibers and has low conductivity, the electromagnetic flowmeter automatically adopts a double-frequency rectangular wave excitation mode to measure; when the fluid detected by the fluid property sensor group (1) is extremely special and cannot be matched with the preset fluid of the electromagnetic flowmeter, the fluid property sensor group (1) transmits the detected fluid information to the microprocessor (3) through the signal processing circuit (2), and the electromagnetic flowmeter automatically performs flow rate measurement in a sweep frequency mode.
3. The self-adaptive electromagnetic flowmeter according to claim 1, wherein the signal processing circuit (2) is composed of a high-pass filter circuit (11), a low-pass filter circuit (12) and an amplifying circuit (13), the output signal of the fluid property sensor group (1) is received by the signal processing circuit (2), tiny direct current components mixed in the signal are filtered by the high-pass filter circuit (11), high-frequency spike interference is filtered by the low-pass filter circuit (12), and finally the signal after the signal is amplified by the amplifying circuit (13) so as to achieve the purposes of signal fidelity and analysis and processing convenience; the signal processing circuit (2) selects an odd harmonic amplitude which is least interfered by fluid noise to reflect the magnitude of a flow signal according to the frequency spectrum characteristic of the output signal of the fluid property sensor group (1), so that the electromagnetic flowmeter can accurately extract flow information from the output signal to further analyze the obtained basic information of the detected fluid, and the basic information is compared with the fluid parameter designed by the electromagnetic flowmeter to obtain the fluid address code required by the electromagnetic flowmeter at the moment.
4. An adaptive electromagnetic flowmeter according to claim 1, wherein the microprocessor (3) controls the selection of flow rate measurement modes in the electromagnetic flowmeter, namely conventional fluid measurement and unconventional fluid measurement, and provides a waveform design program required to be matched in the D/a excitation signal generator (4) and a sweep signal required in the sweep circuit (5), the microprocessor (3) is used for receiving an address code transmitted by the signal processing circuit (2), and the purpose of adaptively selecting the most suitable excitation mode design program is achieved according to the matching of the received address code and the internal programming program of the microprocessor (3), so as to control the D/a excitation signal generator (4) to output an optimal excitation waveform suitable for the D/a excitation signal generator, when the received address code cannot be matched with the existing design program, the electromagnetic flowmeter automatically selects the sweep mode to perform flow rate measurement, and the microprocessor (3) provides an input signal for the sweep circuit (5) with the sweep signal required by programming control.
5. The self-adaptive electromagnetic flowmeter according to claim 1, wherein the D/a excitation signal generator (4) is composed of a high-precision digital-to-analog conversion chip and an external circuit, and is provided with five different excitation waveforms, namely direct current excitation, power frequency sine wave excitation, low-frequency rectangular wave excitation, double-frequency rectangular wave excitation and bidirectional trapezoidal wave excitation, so as to be self-adaptive to different excitation modes required by different fluid flowing through the pipeline, the D/a excitation signal generator (4) also has the rectangular wave excitation modes for outputting different frequencies when the unconventional fluid flows through the pipeline to perform flow velocity measurement on the unconventional fluid, the D/a excitation signal generator (4) receives an excitation programming program transmitted by the microprocessor (3) to generate required excitation waves through the high-precision digital-to-analog conversion chip, and the generated excitation waves are loaded on a coil of the electromagnetic flowmeter to perform flow velocity measurement, so that the electromagnetic flowmeter can perform flow velocity measurement in different fluid environments by using the best-matched excitation modes.
6. The self-adaptive electromagnetic flowmeter according to claim 1, wherein the sweep frequency circuit (5) is formed by taking a microprocessor (3) as a core and by a direct digital frequency synthesizer (14), a low-pass filter (15), a rectifying filter (16) and an AD conversion circuit (17), after the microprocessor (3) receives an address code transmitted by the signal processing circuit (2), corresponding programming is started, corresponding frequencies are synthesized by the AD conversion circuit (17) after initial frequency, ending frequency and frequency interval are input to obtain sweep frequency signals with different frequencies required by the electromagnetic flowmeter, according to different flow rates and fluid properties, the microprocessor (3) generates different sweep frequency ranges and time intervals and loads the different sweep frequency signals to the D/A excitation signal generator (4), when the flow rates are fast, the sweep frequency ranges are large, the sweep frequency ranges are from 6.25Hz to 2KHz, the frequency step size is 0.2Hz, and the time interval between different frequencies is 0.1s; when the fluid flow speed is slower, the frequency sweep frequency range is smaller, the frequency sweep is 6.25Hz to 1KHz, the step length is 0.25Hz, the time interval between different frequencies is 0.2s, the frequency sweep signals generated by the frequency sweep circuit (5) are used for obtaining excitation waveforms under different frequencies and loading the excitation waveforms in the excitation coil, and relevant data obtained through multi-frequency excitation waveform measurement are transmitted to the data processing module.
7. The self-adaptive electromagnetic flowmeter according to claim 1, wherein the data processing module (6) performs excitation sampling on an excitation unit of the electromagnetic flowmeter to obtain analog signals of excitation current and voltage during conventional fluid measurement, corresponding digital signals are obtained after analog-to-digital conversion, fluid flow rate in the sampling period is calculated according to the excitation current and the voltage of the digital signals in the same sampling period after conversion, the data processing circuit performs analysis and comparison on voltage signals in multiple groups of excitation frequencies during non-conventional fluid measurement to select the highest signal-to-noise ratio, the waveform has the smallest change with time, namely the best stability, the excitation frequency corresponding to the most concentrated power spectrum is used as an excitation mode of special fluid, and further the excitation current and the voltage at the frequency are used as analog signals of the data processing module, and the fluid flow rate is obtained by adopting the same data processing method as the conventional fluid.
8. A measurement method using an adaptive electromagnetic flowmeter according to any of claims 1-7, comprising the steps of:
step1, when fluid passes through a pipeline, firstly detecting the property of the fluid by a fluid property sensor group (1), then carrying out filtering and amplifying treatment on the obtained fluid signal by a high-pass filter circuit (11), a low-pass filter circuit (12) and an amplifying circuit (13) in a signal processing circuit (2) to obtain fluid information which is matched with an address code arranged in the device, and then carrying out control identification on the address code by a microprocessor (3);
the step2.D/A excitation signal generator (4) receives a program adopted by the microprocessor (3) to generate excitation signals, the generated excitation signals are loaded on the excitation coil to measure the flow velocity, the obtained data are analyzed and processed through the data processing module (6), and the final result is displayed through the LCD display screen (7).
9. The method for measuring an adaptive electromagnetic flowmeter of claim 8, wherein: in Step1, a fluid adaptation Step is further included, namely: when the signal processing circuit (2) transmits the acquired signals to the microprocessor (3), the electromagnetic flowmeter performs the process of matching the fluid with the set address codes, the microprocessor (3) selectively invokes an excitation generation program suitable for the received fluid information and transmits the excitation generation program to the D/A excitation signal generator (4) only when the received fluid information is matched with the set address codes, and when the received fluid information is not matched with the set contents, the device automatically generates sweep signals, loads the sweep signals to the sweep circuit (5) and cooperates with the D/A excitation signal generator (4) to generate multi-frequency excitation signals for measurement.
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| CN112461305B (en) * | 2020-11-16 | 2022-04-29 | 西南石油大学 | Multi-coil array flow electromagnetic measurement device and measurement method |
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