CN115144041A

CN115144041A - Multi-channel ultrasonic flowmeter system

Info

Publication number: CN115144041A
Application number: CN202210771314.6A
Authority: CN
Inventors: 鲍喜荣; 赵子钧; 张红; 佘黎煌; 张石
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2022-06-30
Filing date: 2022-06-30
Publication date: 2022-10-04

Abstract

The present invention provides a multi-channel ultrasonic flow meter system comprising: a core circuit board and a transceiver circuit board; the receiving and transmitting the circuit board includes: the transmitting circuit, the switching circuit, the receiving circuit and the amplifying selection circuit are connected in sequence; the core board includes: the device comprises an FPGA module, an STM32 module, an ADC module, a 4G module, a USB serial port module, an RS485 module, an LCD module and an SD storage module; the core circuit board and the transceiving circuit board are connected through the pin header and the bus header and are fixed by screws; the core circuit board comprises 21 signals which are connected to 21 corresponding signals of the transceiver board through the pin header. The invention raises the transmitting voltage to 800VPP through the transformer, and can ensure good signal even when measuring the flow rate at a long distance. The invention adds the amplification selection circuit, and can amplify again under the condition of weak echo signals in the long-distance measurement, thereby ensuring the effectiveness of the echo signals.

Description

Multi-channel ultrasonic flowmeter system

Technical Field

The invention relates to the technical field of flowmeters, in particular to a multi-channel ultrasonic flowmeter system.

Background

The ultrasonic flowmeter belongs to a flowmeter of a new generation, is developed rapidly in recent years, and has been widely applied to various fields and the like. In the measuring process, the ultrasonic flowmeter does not need to be in direct contact with fluid, and the measuring performance is greatly improved through digitization and electronization.

At present, most of ultrasonic flowmeters produced by domestic manufacturers adopt a time difference method measuring principle, a voltage conversion chip is usually adopted in a transmitting circuit to provide lower voltage for a transducer to drive the transducer to emit ultrasonic waves, and a single chip microcomputer is usually used as a system core to perform signal processing, so that only some simpler algorithms can be performed. However, the high-quality gas ultrasonic signal processing unit needs to process a weak and complicated ultrasonic echo signal.

In the prior art, a transmitting circuit cannot provide high voltage, so that when the measuring distance is large, a signal is weak. And a single core chip is employed in the entire system, resulting in a degradation of the overall system performance.

Disclosure of Invention

In light of the above-noted problems in the art, a multi-channel ultrasonic flow meter system is provided. The present invention primarily utilizes a multi-channel ultrasonic flow meter system comprising: a core circuit board and a transceiver circuit board; the transceiving circuit board comprises: the transmitting circuit, the switching circuit, the receiving circuit and the amplifying selection circuit are connected in sequence; the core board includes: the device comprises an FPGA module, an STM32 module, an ADC module, a 4G module, a USB serial port module, an RS485 module, an LCD module and an SD storage module;

the core circuit board and the transceiving circuit board are connected through the pin header and the bus header and are fixed by screws; the core circuit board comprises 21 signals which are connected to 21 signals corresponding to the transceiver board through the pin header;

an E10 pin of the FPGA module in the core circuit board is responsible for generating a PWM signal and transmitting the PWM signal to the transceiver board; 16 pins in the FPGA module are connected to 8 relays of a switching circuit of the transceiver board and are used for controlling the real-time switching of the transceiving states of 8 transducers; namely, 8 pins in the FPGA module are used for controlling corresponding 8 transducers to transmit ultrasonic waves, and the other 8 pins are used for controlling the transducers to receive the ultrasonic waves;

the multi-channel ultrasonic flow meter system also has a transducer drive voltage circuit; the transducer driving voltage circuit is driven by high voltage.

Compared with the prior art, the invention has the following advantages:

(1) The invention raises the transmitting voltage to 800VPP through the transformer, and can ensure good signal even when measuring the flow rate at a long distance.

(2) The invention adds the amplification selection circuit, and can amplify again under the condition of weak echo signals in the long-distance measurement, thereby ensuring the effectiveness of the echo signals.

(3) The relay is used under high voltage to switch the state of the transducer, so that the transducer can accurately transmit and receive ultrasonic waves in real time.

(4) And the FPGA and ARM dual core is used for processing and transmitting data, so that the real-time performance, the reliability and the integration level are improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic diagram of a transmit circuit of the present invention;

FIG. 2 is a schematic diagram of a switching circuit of the relay according to the present invention;

FIG. 3 is a schematic diagram of a receiving circuit according to the present invention;

FIG. 4 is a schematic diagram of an amplifying selection circuit according to the present invention;

FIG. 5 is a schematic diagram of the overall operation of the core board according to the present invention;

FIG. 6 shows a PWM signal according to the present invention;

FIG. 7 illustrates the AC at 800VPP according to the present invention;

FIG. 8 shows the spindle shape of the echo signal after the primary amplification and the pre-amplification of the triode according to the present invention;

FIG. 9 is a waveform of an echo signal after band-pass filtering according to the present invention;

FIG. 10 is a schematic view of the operation of the transceiver board of the present invention;

fig. 11 is a simplified structure of the ultrasonic transducer mounting of the present invention.

Detailed Description

In order to make those skilled in the art better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

As shown in fig. 1-11, the present invention provides a multi-channel ultrasonic flow meter system, comprising: a core circuit board and a transceiver circuit board; the receiving and transmitting circuit board is used for transmitting ultrasonic waves, receiving echo signals, primarily amplifying, filtering, amplifying again and then transmitting to the ADC. The method comprises the following steps: the transmitting circuit, the switching circuit, the receiving circuit and the amplifying selection circuit are connected in sequence; the core board includes: FPGA module, STM32 module, ADC module, 4G module, USB serial port module, RS485 module, LCD module, SD storage module. After the system is started, the FPGA chip generates a PWM signal and transmits the PWM signal to the transmitting circuit, and then the transformer starts to work to generate high-voltage excitation to drive the transducer to transmit ultrasonic waves.

The switching circuit is critical because it is connected to both the control signals of the core board and switches the transducers between receiving and transmitting.

The FPGA selects a sound channel firstly, and performs sound channel switching every 1 second according to the sequence of the first sound channel, the second sound channel, the third sound channel and the fourth sound channel, and completes a sound channel switching cycle for 4 seconds. Meanwhile, in each sound channel, the state of transmitting and receiving ultrasonic waves is switched every 0.5 second for the two transducers of the sound channel.

Taking the first sound channel as an example, the FPGA selects the first sound channel, and controls the two transducers 1A and 1B of the first sound channel, so that the 1A transducer transmits the ultrasonic wave in the first 0.5 seconds, and the 1B transducer receives the ultrasonic wave, and then switches the transceiving state and maintains for 0.5 seconds, and the 1A transducer receives the ultrasonic wave and the 1B transducer transmits the ultrasonic wave. The sound channel two, the sound channel three and the sound channel four are the same, and the circulation is repeated after 4 seconds.

The system has a total of 8 transducers, and each transducer can transmit and receive ultrasound waves. Therefore, in a period of 4 seconds, 8 echo signals are generated, and the 8 echo signals sequentially enter the receiving circuit for processing, then enter the amplification selection circuit for signal amplification, and finally enter the ADC.

In addition, fig. 11 is added to the drawings to explain the work flow of this paragraph.

an E10 pin of the FPGA module in the core circuit board is responsible for generating a PWM signal and transmitting the PWM signal to the transceiver board; 16 pins in the FPGA module are connected to 8 relays of a switching circuit of the transceiver board and are used for controlling the real-time switching of the transceiver states of 8 transducers; namely, 8 pins in the FPGA module are used for controlling corresponding 8 transducers to transmit ultrasonic waves, and the other 8 pins are used for controlling the transducers to receive the ultrasonic waves;

2. The multi-channel ultrasonic flow meter system of claim 1 in which the ultrasonic transducers in the multi-channel ultrasonic flow meter system operate at a frequency of 200kHz.

The PWM signal in the transmitting circuit is connected to one pin of the MOS tube and used for controlling the conduction and the cut-off of the MOS tube, and the other pin of the MOS tube is connected to one end of the primary level of the transformer; the other end of the primary level of the transformer is connected with a 24V direct-current power supply; after inversion, the secondary side of the transformer can output the alternating current with the peak-to-peak value of 800V.

The multi-channel ultrasonic flowmeter is based on a time difference principle;

the diameter of a preset pipe section is D, the cross-sectional area of the pipe section is S, the actual flow velocity of gas in the pipe section is V, the direction is from left to right, and the flow is Q; the installation angle of the two sensors A and B is theta, theta is not zero, the distance between the two ultrasonic transducers is L, and the propagation speed of ultrasonic waves in a static fluid is C ₀ (ii) a When transducer a transmits ultrasound, transducer B receives, that is, the propagation velocity of the ultrasonic wave along L is C = C in the downstream ₀ + Vcos θ; when transducer B transmits an ultrasonic wave and transducer a receives, i.e. counter-flows, the propagation velocity of the ultrasonic wave along L is C = C ₀ -Vcosθ；

The forward propagation time and the backward propagation time of the ultrasonic wave are as follows:

t _AB ＝L/(C ₀ +Vcosθ) (1)；

t _BA ＝L/(C ₀ -Vcosθ) (2)；

the time difference obtained from equations (1) and (2) is:

in the formula (3), the first and second groups,

equation (3) can thus be simplified to:

from equation (4) the flow rate can be found as:

by combining the flow velocity V, the cross-sectional area S, and the flow correction coefficient k of the acoustic channel, the flow can be calculated as:

the transmitting and receiving board mainly comprises a transmitting circuit, a switching circuit, a receiving circuit and an amplifying and selecting circuit, wherein the transmitting circuit is responsible for driving the transducer to emit ultrasonic waves, the driving voltage directly influences the quality of ultrasonic signals, and the reliability of the ultrasonic flowmeter is indirectly influenced. Therefore, it is very important to design an adaptive transducer driving voltage circuit, and the design adopts a high-voltage driving scheme and needs a transformer with the frequency of 200kHz.

Fig. 1 is a schematic diagram of a transmit circuit. The PWM signal is connected to one pin of the MOS tube and used for controlling the conduction and the cut-off of the MOS tube, and the other pin of the MOS tube is connected to one end of the primary level of the transformer. The other end of the primary level of the transformer is connected with a 24V direct-current power supply. After inversion, the secondary side of the transformer can output the alternating current with the peak-to-peak value of 800V.

The multi-channel ultrasonic flowmeter is based on the time difference principle and requires 2 transducers to be arranged in each sound channel. Taking four channels as an example, a total of 8 transducers are required. Now, according to the affiliation, the four sound channels and the 8 transducers are named as a sound channel-to-corresponding transducer 1A and a transducer 1B in sequence; the sound channel two-corresponding transducer 2A and the transducer 2B; the sound channel three corresponds to the transducer 3A and the transducer 3B; channel four corresponds to transducer 4A, transducer 4B.

This design requires that all transducers be able to transmit and receive sound waves, so a switching circuit is required to switch the use state of the transducers. Because the voltage resistance of the analog switch is limited, the design adopts relay switching. The design totally uses 8 relays, corresponding to 8 transducers, namely, each transducer has a dedicated relay. Each relay has two switches for controlling the same transducer to switch between transmitting and receiving ultrasonic waves. Taking the transducer 1A with the first sound channel as an example, fig. 2 is a schematic diagram of a relay switching circuit. No. 8 pin of the electric relay is connected to 800VPP alternating current, no. 6 and No. 7 pins are connected to the terminal of the transducer 1A, no. 5 pin is connected to the echo signal REC, and No. 1 and No. 3 pins are connected to the direct current power supply 3.3V. And the No. 2 pin is connected with a 1.5k resistor and then connected to a C11 pin of the FPGA to be used as a control signal, and when the signal is at a low level, the transducer 1A emits ultrasonic waves. The pin 4 is connected with a resistor 1.5k and then connected to a pin F10 of the FPGA to serve as a control signal, and when the signal is at a low level, the transducer 1A receives ultrasonic waves.

Fig. 3 is a schematic diagram of a receiving circuit. The receiving circuit mainly comprises an amplitude limiting circuit, a triode primary amplifying circuit, a pre-amplifying circuit and a band-pass filtering circuit. The echo signal REC first passes through a limiting circuit, the voltage of which is limited to ± 0.7V. Then, the echo signal passes through a triode primary amplifying circuit, and the voltage of the echo signal is amplified by 30 times. The echo signal then passes through a pre-amplifier circuit, the voltage of which will be amplified by a factor of 100. Finally, the echo signal passes through a band-pass filter circuit, the center frequency of which is 200kHz and the bandwidth of which is 60kHz. Finally, the signal REC _ M processed by the receiving circuit is obtained.

Fig. 4 is a schematic diagram of an amplification selection circuit. The REC _ M signal can enter different amplifying circuits through switch selection. Selecting (1) as an REC _ M signal to directly enter an ADC; selecting the REC _ M signal in the step (2) to enter a logarithmic amplification circuit and then enter an ADC; and (3) selecting the REC _ M signal to enter the PGA amplifying circuit and then enter the ADC. If the voltage amplitude of the REC _ M signal is small, the REC _ M signal enters the ADC after logarithmic amplification or PGA amplification; if the voltage amplitude of the REC _ M signal is enough, the voltage can directly enter the ADC without logarithmic amplification or PGA amplification. The signal that finally enters the ADC is named signal REC _ ADC here.

The core board mainly comprises an FPGA module, an STM32 module, an ADC module, a 4G module, a USB serial port module, an RS485 module, an LCD module and an SD storage module, and the overall working schematic diagram of the core board is shown in figure 5.

And an E10 pin of the FPGA chip is responsible for generating a PWM signal and transmitting the PWM signal to the transceiver board. There are 8 pins in the FPGA chip to control the corresponding 8 transducers to transmit ultrasonic waves, and there are 8 pins to control the transducers to receive ultrasonic waves.

The signal REC _ ADC is an analog signal, the FPGA chip controls the ADC to perform analog-to-digital conversion on the signal, the converted signal is processed, and finally data are transmitted to the STM32 chip through the FMC. The STM32 chip is connected a large amount of peripheral hardware, with received data storage on the SD card to through the external measuring velocity of flow that shows of LCD module, transmit to the PC end through USB serial port module, can externally mark through the RS485 module, and can be through the external wireless transmission data of 4G module.

Example 1

As shown in fig. 6, fig. 6 shows a PWM signal with a frequency of 200kHz and a duty ratio of 50% for controlling the on/off of the MOS transistor to generate an ac power of 800VPP, as shown in fig. 7.

When the distance between the transducer and the ultrasonic transducer is 13 cm, the echo signal presents a spindle shape after being subjected to primary amplification and pre-amplification by the triode, the amplitude is 1.76VPP, as shown in figure 8, and then the waveform is good after being subjected to band-pass filtering, as shown in figure 9.

The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments. In the above embodiments of the present invention, the description of each embodiment has its own emphasis, and reference may be made to the related description of other embodiments for parts that are not described in detail in a certain embodiment. In the embodiments provided in the present application, it should be understood that the disclosed technical content can be implemented in other manners.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-channel ultrasonic flow meter system, comprising: a core circuit board and a transceiver circuit board; the transceiving circuit board comprises: the transmitting circuit, the switching circuit, the receiving circuit and the amplifying selection circuit are connected in sequence; the core board includes: the device comprises an FPGA module, an STM32 module, an ADC module, a 4G module, a USB serial port module, an RS485 module, an LCD module and an SD storage module;

the core circuit board and the transceiving circuit board are connected through the pin header and the bus header and are fixed by screws; the core circuit board comprises a plurality of signals which are connected to a plurality of signals corresponding to the transceiver board through the pin header;

an E10 pin of the FPGA module in the core circuit board is responsible for generating a PWM signal and transmitting the PWM signal to the transceiver board; a plurality of pins in the FPGA module are connected to a plurality of relays of a switching circuit of the transceiver board and are used for controlling the real-time switching of the transceiver states of a plurality of transducers; namely, a plurality of pins in the FPGA module are used for controlling a plurality of corresponding transducers to transmit ultrasonic waves, and a plurality of pins are used for controlling the transducers to receive the ultrasonic waves;

3. The multi-channel ultrasonic flowmeter system of claim 1 wherein the PWM signal in the transmitter circuit is connected to one pin of the MOS transistor for controlling the on and off of the MOS transistor, and the other pin of the MOS transistor is connected to one end of the primary transformer; the other end of the primary level of the transformer is connected with a 24V direct-current power supply; after inversion, the secondary side of the transformer can output the alternating current with the peak-to-peak value of 800V.

4. The multi-channel ultrasonic flow meter system of claim 1 wherein the multi-channel ultrasonic flow meter is based on the time difference principle;

the diameter of a preset pipe section is D, the cross-sectional area of the pipe section is S, the actual flow velocity of gas in the pipe section is V, the direction is from left to right, and the flow is Q; the installation angle of the two sensors A and B is theta, theta is not zero, the distance between the two ultrasonic transducers is L, and the propagation speed of ultrasonic waves in a static fluid is C ₀ (ii) a When transducer a transmits ultrasonic waves and transducer B receives, i.e. downstream, the propagation velocity of the ultrasonic waves along L is C = C ₀ + Vcos θ; when transducer B transmits an ultrasonic wave and transducer a receives, i.e. counter-flows, the propagation velocity of the ultrasonic wave along L is C = C ₀ -Vcosθ；

t _AB ＝L/(C ₀ +Vcosθ) (1)；

t _BA ＝L/(C ₀ -Vcosθ) (2)；

the time difference obtained from equations (1) and (2) is:

in the formula (3), the first and second groups of the compound,

thus, formula (3)Can be simplified as follows:

from equation (4) the flow rate can be found as:

5. the multi-channel ultrasonic flow meter system of claim 1,

the ultrasonic flowmeter system switches the use state of the transducer through a relay; the multi-channel ultrasonic flowmeter system comprises 8 relays and corresponds to 8 transducers; each relay is provided with two switches which are used for controlling the same transducer to switch between transmitting and receiving ultrasonic waves.

6. The multi-channel ultrasonic flow meter system of claim 1,

the receiving circuit includes: the circuit comprises an amplitude limiting circuit, a triode primary amplifying circuit, a preamplification circuit and a band-pass filter circuit; the echo signal REC firstly passes through a limiting circuit, and the voltage of the echo signal REC is limited within +/-0.7V; the voltage of the wave signal is amplified by 30 times through a triode primary amplifying circuit; the voltage of the echo signal is amplified by 100 times through a preamplification circuit; finally, the echo signal passes through a band-pass filter circuit, the center frequency of the band-pass filter circuit is 200kHz, and the bandwidth is 60kHz; finally, the signal REC _ M processed by the receiving circuit is obtained.

7. The multi-channel ultrasonic flow meter system of claim 1,

in the amplification selection circuit, the REC _ M signal enters different amplification circuits through switch selection; selecting (1) as an REC _ M signal to directly enter an ADC; selecting the REC _ M signal in the step (2) to enter a logarithmic amplification circuit and then enter an ADC; selecting the REC _ M signal in the step (3) to enter a PGA amplifying circuit and then enter an ADC; if the voltage amplitude of the REC _ M signal is small, the REC _ M signal enters the ADC after logarithmic amplification or PGA amplification; if the voltage amplitude of the REC _ M signal is enough, the REC _ M signal can directly enter the ADC without logarithmic amplification or PGA amplification; the signal that finally enters the ADC is named signal REC _ ADC here.