Circuit and method for measuring gas flow through ultrasonic waves

Abstract

The invention relates to the technical field of integrated circuit design, and particularly discloses a circuit and method for measuring gas flow through ultrasonic waves, and the circuit comprises an uplink transducer which is used for receiving an uplink differential pulse sequence to excite and generate an uplink ultrasonic signal, and receiving and forwarding a downlink ultrasonic signal; the downlink transducer is used for receiving the downlink differential pulse sequence to excite and generate the downlink ultrasonic signal, and receiving and forwarding the uplink ultrasonic signal; the controller is used for controlling the generation of an uplink differential pulse sequence and a downlink differential pulse sequence, receiving a downlink ultrasonic signal forwarded by the uplink transducer and an uplink ultrasonic signal forwarded by the downlink transducer which are sequentially subjected to amplification and analog-to-digital conversion, and generating a differential pulse sequence based on the received downlink ultrasonic signal and the uplink ultrasonic signal; and corresponding flight time is calculated, so that the actual gas flow is calculated. The differential excitation transducer is adopted, the signal transmitting amplitude of the transducer is greatly increased, and therefore the signal-to-noise ratio is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuit design, and in particular to a circuit and method for ultrasonically measuring gas flow. Background Art

[0002] Ultrasonic gas meters, with their advanced technology and significant advantages, are a key development direction for gas metering. However, due to the significant attenuation of ultrasonic signals by gases, gas flow measurements often face the issue of low signal-to-noise ratios. This is further reduced during complex gas measurements, leading to unstable time-of-flight calculations and, consequently, compromising the accuracy and stability of gas flow measurements.

[0003] Existing technologies typically use a single-ended excitation transducer, where the positive terminal receives the excitation signal and the negative terminal is grounded. In battery-powered systems like ultrasonic gas meters, the signal amplitude emitted by a single-ended excitation transducer is limited, affecting the accuracy and stability of flow measurement.

[0004] Invention application CN105115553A measures gas flow by the time difference method. Although it can improve the accuracy of flow testing to a certain extent, its first ultrasonic transducer, second ultrasonic transducer, third ultrasonic transducer and fourth ultrasonic transducer all adopt single-ended excitation transducer mode. When the excitation signal is weak, the problem of limited amplitude of the emitted signal cannot be avoided, which in turn causes insufficient accuracy and poor stability of the flow test.

[0005] Based on this technical background, the present invention studies a circuit and method for ultrasonically measuring gas flow. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention proposes a circuit and method for ultrasonic measurement of gas flow. The circuit adopts a differential excitation transducer, which can significantly increase the amplitude of the transducer's transmitted signal without changing the power supply voltage, thereby improving the signal-to-noise ratio and further enhancing the accuracy and stability of flow measurement.

[0007] In order to achieve the above object, the present invention provides a first aspect of a circuit for ultrasonically measuring gas flow, comprising: An uplink transducer, configured to receive an uplink differential pulse sequence and stimulate the generation of the uplink ultrasonic signal, and also configured to receive and forward a downlink ultrasonic signal; A downlink transducer, configured to receive a downlink differential pulse sequence and stimulate the generation of the downlink ultrasonic signal, and further configured to receive and forward the uplink ultrasonic signal; a controller for controlling the generation of the uplink differential pulse sequence and the downlink differential pulse sequence, for receiving the downlink ultrasonic signal forwarded by the uplink transducer and the uplink ultrasonic signal forwarded by the downlink transducer after sequentially amplification and analog-to-digital conversion, and for calculating corresponding flight times based on the received downlink ultrasonic signal and uplink ultrasonic signal, thereby calculating the actual gas flow rate; The uplink transducer is excited to generate the uplink ultrasonic signal, which is different from the downlink transducer being excited to generate the downlink ultrasonic signal.

[0008] A second aspect of the present invention provides a method for ultrasonically measuring gas flow in the above-mentioned circuit, comprising: The controller controls the generation of an uplink differential pulse sequence and sends it to the uplink transducer; After receiving the uplink differential pulse sequence, the uplink transducer is excited to generate an uplink ultrasonic signal, while the downlink transducer receives and forwards the uplink ultrasonic signal; amplifying and converting the forwarded uplink ultrasonic signal into digital form, and then sending the signal to the controller; The controller controls the generation of a downlink differential pulse sequence and sends it to the downlink transducer; After receiving the downlink differential pulse sequence, the downlink transducer is excited to generate a downlink ultrasonic signal, and at the same time the uplink transducer receives and forwards the downlink ultrasonic signal; amplifying and converting the forwarded downlink ultrasonic signal into digital form, and then sending the signal to the controller; The controller calculates the corresponding flight time based on the received downlink ultrasonic signal and uplink ultrasonic signal, thereby calculating the actual gas flow rate; The uplink transducer is excited to generate the uplink ultrasonic signal, which is different from the downlink transducer being excited to generate the downlink ultrasonic signal.

[0009] The beneficial effects of the present invention include: The ultrasonic gas flow measurement circuit proposed in the present invention controls the generation of an uplink differential pulse sequence and a downlink differential pulse sequence, and receives the downlink ultrasonic signal forwarded by the uplink transducer and the uplink ultrasonic signal forwarded by the downlink transducer after being amplified and analog-to-digital converted in sequence. At the same time, based on the received downlink ultrasonic signal and uplink ultrasonic signal, the corresponding flight time is calculated to calculate the actual gas flow. The overall circuit adopts a differential excitation transducer method, which can greatly increase the amplitude of the transducer transmission signal without changing the power supply voltage, thereby improving the signal-to-noise ratio, and further improving the accuracy and stability of the flow measurement.

[0010] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0012] Figure 1 This is a structural diagram of a specific embodiment of the circuit for ultrasonically measuring gas flow proposed by the present invention.

[0013] Description of reference numerals: K1-first SPDT switch, K2-second SPDT switch, K3-third SPDT switch, K4-fourth SPDT switch, K5-first SPDT switch, K6-second SPDT switch, R-resistor. DETAILED DESCRIPTION

[0014] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0015] In the present invention, unless otherwise specified, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of a device in normal use, and "inner" and "outer" refer to positions relative to the device's outline. Furthermore, the terms "first, second, and third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly specifying the number of the technical features indicated. Therefore, features defined as "first, second, and third" may explicitly or implicitly include one or more of such features. In the description of the present invention, "plurality" means two or more, unless otherwise explicitly and specifically defined.

[0016] The present invention provides a circuit for ultrasonically measuring gas flow, such as Figure 1 As shown, including: An uplink transducer, configured to receive an uplink differential pulse sequence and stimulate the generation of the uplink ultrasonic signal, and also configured to receive and forward a downlink ultrasonic signal; A downlink transducer, configured to receive a downlink differential pulse sequence and stimulate the generation of the downlink ultrasonic signal, and further configured to receive and forward the uplink ultrasonic signal; a controller for controlling the generation of an uplink differential pulse sequence and a downlink differential pulse sequence, and for receiving the downlink ultrasonic signal forwarded by the uplink transducer and the uplink ultrasonic signal forwarded by the downlink transducer after sequentially being amplified and analog-to-digital converted, and further for calculating the corresponding flight time based on the received downlink ultrasonic signal and uplink ultrasonic signal, thereby calculating the actual gas flow rate; The uplink transducer is excited to generate an uplink ultrasonic signal, which is different from the downlink transducer being excited to generate a downlink ultrasonic signal.

[0017] In the present invention, by controlling the generation of an uplink differential pulse sequence and a downlink differential pulse sequence, and receiving the downlink ultrasonic signal forwarded by the uplink transducer and the uplink ultrasonic signal forwarded by the downlink transducer after sequential amplification and analog-to-digital conversion, and at the same time calculating the corresponding flight time based on the received downlink ultrasonic signal and uplink ultrasonic signal, the actual gas flow rate is calculated. The overall circuit adopts a differential excitation transducer method, which can greatly increase the amplitude of the transducer transmission signal without changing the power supply voltage, thereby improving the signal-to-noise ratio, and further improving the accuracy and stability of the flow measurement.

[0018] According to the present invention, it also includes: The first single-pole double-throw switch K1 has a normally closed point connected to one end of the upstream transducer and a normally open point connected to one end of the downstream transducer; The second single-pole double-throw switch K2 has its normally closed point connected to the other end of the upstream transducer and its normally open point connected to the other end of the downstream transducer; A third single-pole double-throw switch K3, whose normally closed point is connected to one end of the downstream transducer and whose normally open point is connected to one end of the upstream transducer; The fourth single-pole double-throw switch K4 has a normally closed point connected to the other end of the downstream transducer, a normally open point connected to the other end of the upstream transducer, and a knife end connected to the ground.

[0019] According to the present invention, it also includes: The first single-pole single-throw switch K5 has a blade end connected to one end of the upstream transducer and a pull-in end connected to the other end of the upstream transducer via a resistor R; The second single-pole single-throw switch K6 has a blade end connected to one end of the downstream transducer, and a pull-in end connected to the other end of the downstream transducer via a resistor R; The first single-pole double-throw switch K1 , the second single-pole double-throw switch K2 , the third single-pole double-throw switch K3 , the fourth single-pole double-throw switch K4 , the first single-pole double-throw switch K5 and the second single-pole single-throw switch K6 are all controlled by the controller.

[0020] According to the present invention, it also includes: The pulse generator has a control end connected to the controller and is used to generate an uplink pulse sequence and a downlink pulse sequence under the control of the controller; A driver, whose input end is connected to the output end of the pulse generator, and whose output end is connected to the knife end of the first single-pole double-throw switch K1 via a resistor R, is used to generate an in-phase pulse sequence with enhanced driving capability and a phase difference of 0 degree with the uplink pulse sequence and the downlink pulse sequence; The inverter has an input end connected to the output end of the pulse generator, and an output end connected to the knife end of the second single-pole double-throw switch K2 through a resistor R, and is used to generate an inverted pulse sequence with a phase difference of 180 degrees with the uplink pulse sequence and the downlink pulse sequence.

[0021] According to the present invention, it also includes: An amplifier, whose input end is connected to the knife end of the third single-pole double-throw switch K3 via a resistor R, is used to amplify the downlink ultrasonic signal forwarded by the uplink transducer and the uplink ultrasonic signal forwarded by the downlink transducer; The ADC acquisition module has an input end connected to the output end of the amplifier and an output end connected to the controller. It is used to perform analog-to-digital conversion on the signal output by the amplifier and send the digital signal to the controller.

[0022] In the present invention, the value of the series resistor on each signal transmission path is 10-100 ohms, which is used to form an RC circuit with the distributed capacitance, thereby smoothing the signal edge and reducing high-frequency noise and overshoot problems.

[0023] The present invention also provides a method for ultrasonically measuring gas flow in the above circuit, comprising: The controller controls the generation of an uplink differential pulse sequence and sends it to the uplink transducer; After receiving the uplink differential pulse sequence, the uplink transducer is excited to generate an uplink ultrasonic signal, while the downlink transducer receives and forwards the uplink ultrasonic signal; The forwarded uplink ultrasonic signal is amplified and converted into analog-to-digital signals in sequence, and then sent to the controller; The controller controls the generation of a downlink differential pulse sequence and sends it to the downlink transducer; After receiving the downlink differential pulse sequence, the downlink transducer is excited to generate a downlink ultrasonic signal, while the uplink transducer receives and forwards the downlink ultrasonic signal; The forwarded downlink ultrasonic signal is amplified and converted into analog-to-digital signals in sequence, and then sent to the controller; The controller calculates the corresponding flight time based on the received downlink ultrasonic signal and uplink ultrasonic signal, thereby calculating the actual gas flow rate; The uplink transducer is excited to generate an uplink ultrasonic signal, which is different from the downlink transducer being excited to generate a downlink ultrasonic signal.

[0024] According to the present invention, the controller controls the generation of an uplink differential pulse sequence and sends it to the uplink transducer, including: The controller controls the generation of an uplink differential pulse sequence, and simultaneously controls the normally closed points of the first single-pole double-throw switch K1 and the second single-pole double-throw switch K2 to be energized, and the first single-pole single-throw switch K5 to be energized, thereby sending the uplink differential pulse sequence to the uplink transducer; The uplink transducer excites and generates an uplink ultrasonic signal, and the downlink transducer receives and forwards the uplink ultrasonic signal, including: While the uplink transducer is excited to generate an uplink ultrasonic signal, the controller controls the normally closed points of the third single-pole double-throw switch K3 and the fourth single-pole double-throw switch K4 to be closed and the second single-pole single-throw switch K6 to be disconnected, so that the downlink transducer receives and forwards the uplink ultrasonic signal.

[0025] According to the present invention, the controller controls the generation of a downlink differential pulse sequence and sends it to the downlink transducer, including: The controller controls the generation of a downstream differential pulse sequence, and simultaneously controls the normally open points of the third single-pole double-throw switch K3 and the fourth single-pole double-throw switch K4 to be closed, and the second single-pole single-throw switch K6 to be closed, thereby sending the downstream differential pulse sequence to the downstream transducer; The downlink transducer excites and generates a downlink ultrasonic signal, and the uplink transducer receives and forwards the downlink ultrasonic signal, including: While the downstream transducer is excited to generate a downstream ultrasonic signal, the controller controls the normally open points of the first single-pole double-throw switch K1 and the second single-pole double-throw switch K2 to be closed and the first single-pole single-throw switch K5 to be disconnected, so that the upstream transducer receives and forwards the downstream ultrasonic signal.

[0026] According to the present invention, the controller controls the generation of an uplink differential pulse sequence, including: The controller controls the pulse generator to generate an uplink pulse sequence; The uplink pulse sequence is sent to the driver and the inverter respectively, and an uplink in-phase pulse sequence with enhanced driving capability and a phase difference of 0 degree with the uplink pulse sequence is obtained at the output end of the driver, and an uplink inverted pulse sequence with a phase difference of 180 degrees with the uplink pulse sequence is obtained at the output end of the inverter; The uplink in-phase pulse sequence and the uplink anti-phase pulse sequence together form an uplink differential pulse sequence.

[0027] According to the present invention, the controller controls the generation of the downlink differential pulse sequence, including: The controller controls the pulse generator to generate a downlink pulse sequence; The downlink pulse sequence is sent to the driver and the inverter respectively, and a downlink in-phase pulse sequence with enhanced driving capability and a phase difference of 0 degree with the downlink pulse sequence is obtained at the output end of the driver, and a downlink inverted pulse sequence with a phase difference of 180 degrees with the downlink pulse sequence is obtained at the output end of the inverter; The downlink in-phase pulse sequence and the uplink anti-phase pulse sequence together form a downlink differential pulse sequence.

[0028] The present invention will be described in more detail below through specific examples.

[0029] Example 1

[0030] like Figure 1 As shown, this embodiment provides a circuit for ultrasonically measuring gas flow, including: An uplink transducer, configured to receive an uplink differential pulse sequence and stimulate the generation of the uplink ultrasonic signal, and also configured to receive and forward a downlink ultrasonic signal; A downlink transducer, configured to receive a downlink differential pulse sequence and stimulate the generation of the downlink ultrasonic signal, and further configured to receive and forward the uplink ultrasonic signal; a controller for controlling the generation of an uplink differential pulse sequence and a downlink differential pulse sequence, and for receiving the downlink ultrasonic signal forwarded by the uplink transducer and the uplink ultrasonic signal forwarded by the downlink transducer after sequentially being amplified and analog-to-digital converted, and further for calculating the corresponding flight time based on the received downlink ultrasonic signal and uplink ultrasonic signal, thereby calculating the actual gas flow rate; The uplink transducer is excited to generate an uplink ultrasonic signal, which is different from the downlink transducer being excited to generate a downlink ultrasonic signal. The first single-pole double-throw switch K1 has a normally closed point connected to one end of the upstream transducer and a normally open point connected to one end of the downstream transducer; The second single-pole double-throw switch K2 has its normally closed point connected to the other end of the upstream transducer and its normally open point connected to the other end of the downstream transducer; A third single-pole double-throw switch K3, whose normally closed point is connected to one end of the downstream transducer and whose normally open point is connected to one end of the upstream transducer; A fourth single-pole double-throw switch K4, whose normally closed point is connected to the other end of the downstream transducer, whose normally open point is connected to the other end of the upstream transducer, and whose knife end is connected to the ground; The first single-pole single-throw switch K5 has a blade end connected to one end of the upstream transducer and a pull-in end connected to the other end of the upstream transducer via a resistor R; The second single-pole single-throw switch K6 has a blade end connected to one end of the downstream transducer, and a pull-in end connected to the other end of the downstream transducer via a resistor R; The first single-pole double-throw switch K1, the second single-pole double-throw switch K2, the third single-pole double-throw switch K3, the fourth single-pole double-throw switch K4, the first single-pole single-throw switch K5 and the second single-pole single-throw switch K6 are all controlled by the controller; The pulse generator has a control end connected to the controller and is used to generate an uplink pulse sequence and a downlink pulse sequence under the control of the controller; A driver, whose input end is connected to the output end of the pulse generator, and whose output end is connected to the knife end of the first single-pole double-throw switch K1 via a resistor R, is used to generate an in-phase pulse sequence with enhanced driving capability and a phase difference of 0 degree with the uplink pulse sequence and the downlink pulse sequence; The inverter has an input end connected to the output end of the pulse generator, and an output end connected to the knife end of the second single-pole double-throw switch K2 via a resistor R, and is used to generate an inverted pulse sequence with a phase difference of 180 degrees with the uplink pulse sequence and the downlink pulse sequence; An amplifier, whose input end is connected to the knife end of the third single-pole double-throw switch K3 via a resistor R, is used to amplify the downlink ultrasonic signal forwarded by the uplink transducer and the uplink ultrasonic signal forwarded by the downlink transducer; The ADC acquisition module has an input end connected to the output end of the amplifier and an output end connected to the controller. It is used to perform analog-to-digital conversion on the signal output by the amplifier and send the digital signal to the controller.

[0031] In this embodiment, the value of the series resistor on each signal transmission path is 10-100 ohms, which is used to form an RC circuit with the distributed capacitance, thereby smoothing the signal edge and reducing high-frequency noise and overshoot problems.

[0032] Ultrasonic measurement of gas flow velocity requires measuring the flight time of the ultrasonic uplink and downlink signals separately to calculate the gas flow rate. This embodiment provides a method for ultrasonically measuring gas flow rate, including: When measuring the uplink signal, the normally closed points of the first single-pole double-throw switch K1, the second single-pole double-throw switch K2, the third single-pole double-throw switch K3 and the fourth single-pole double-throw switch K4 are closed, the first single-pole single-throw switch K5 is closed, and the second single-pole single-throw switch K6 is opened. The controller controls the pulse generator to output a pulse sequence. After passing through the driver and inverter, two signals with the same amplitude but a phase difference of 180 degrees are output. These signals are applied to both ends of the uplink transducer, exciting the uplink transducer to output an ultrasonic signal. The downlink transducer receives the ultrasonic signal, which is converted into a digital signal after passing through the amplifier and ADC acquisition module and received by the controller; When measuring the downlink signal, the normally open points of the first single-pole double-throw switch K1, the second single-pole double-throw switch K2, the third single-pole double-throw switch K3 and the fourth single-pole double-throw switch K4 are closed, the second single-pole double-throw switch K6 is closed, and the first single-pole single-throw switch K5 is opened. The controller controls the pulse generator to output a pulse sequence. After passing through the driver and the inverter, two signals with the same amplitude but a phase difference of 180 degrees are output. The signals are applied to both ends of the downlink transducer, exciting the downlink transducer to output an ultrasonic signal. The uplink transducer receives the ultrasonic signal, which is converted into a digital signal after passing through the amplifier and ADC acquisition module and received by the controller; The controller calculates the corresponding flight time based on the collected data of the received uplink and downlink signals, and thus calculates the actual gas flow rate.

[0033] The circuit for ultrasonically measuring gas flow proposed in an embodiment of the present invention controls the generation of an uplink differential pulse sequence and a downlink differential pulse sequence, and receives the downlink ultrasonic signal forwarded by the uplink transducer and the uplink ultrasonic signal forwarded by the downlink transducer, which are sequentially amplified and analog-to-digital converted. At the same time, based on the received downlink ultrasonic signal and uplink ultrasonic signal, the corresponding flight time is calculated to calculate the actual gas flow. The overall circuit adopts a differential excitation transducer method, which can greatly increase the amplitude of the transducer transmission signal without changing the power supply voltage, thereby improving the signal-to-noise ratio, and further improving the accuracy and stability of the flow measurement.

[0034] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A circuit for ultrasonically measuring gas flow, characterized in that: include: An uplink transducer is used to receive an uplink differential pulse sequence and generate an uplink ultrasonic signal, and is also used to receive and forward a downlink ultrasonic signal; A downlink transducer, configured to receive a downlink differential pulse sequence and stimulate the generation of the downlink ultrasonic signal, and further configured to receive and forward the uplink ultrasonic signal; a controller for controlling the generation of the uplink differential pulse sequence and the downlink differential pulse sequence, for receiving the downlink ultrasonic signal forwarded by the uplink transducer and the uplink ultrasonic signal forwarded by the downlink transducer after sequentially amplification and analog-to-digital conversion, and for calculating corresponding flight times based on the received downlink ultrasonic signal and uplink ultrasonic signal, thereby calculating the actual gas flow rate; The uplink transducer is excited to generate the uplink ultrasonic signal, which is different from the downlink transducer being excited to generate the downlink ultrasonic signal.

2. The circuit according to claim 1, wherein: Also includes: a first single-pole double-throw switch, a normally closed point connected to one end of the upstream transducer, and a normally open point connected to one end of the downstream transducer; a second single-pole double-throw switch, a normally closed point connected to the other end of the upstream transducer, and a normally open point connected to the other end of the downstream transducer; a third single-pole double-throw switch, a normally closed point of which is connected to one end of the downstream transducer, and a normally open point of which is connected to one end of the upstream transducer; A fourth single-pole double-throw switch has a normally closed point connected to the other end of the downstream transducer, a normally open point connected to the other end of the upstream transducer, and a knife end connected to the ground.

3. The circuit according to claim 2, characterized in that Also includes: a first single-pole single-throw switch, wherein a knife end is connected to one end of the upstream transducer, and a pull-in end is connected to the other end of the upstream transducer via a resistor; a second single-pole single-throw switch, wherein a knife end is connected to one end of the downstream transducer, and a pull-in end is connected to the other end of the downstream transducer via a resistor; The first single-pole double-throw switch, the second single-pole double-throw switch, the third single-pole double-throw switch, the fourth single-pole double-throw switch, the first single-pole single-throw switch and the second single-pole single-throw switch are all controlled by the controller.

4. The circuit according to claim 3, characterized in that Also includes: A pulse generator, whose control end is connected to the controller, is used to control the controller to generate an uplink pulse sequence and a downlink pulse sequence; a driver, having an input end connected to the output end of the pulse generator and an output end connected to the knife end of the first single-pole double-throw switch via a resistor, for generating an in-phase pulse sequence with enhanced driving capability and a phase difference of 0 degree with the uplink pulse sequence and the downlink pulse sequence; The inverter has an input end connected to the output end of the pulse generator and an output end connected to the knife end of the second single-pole double-throw switch via a resistor, and is used to generate an inverted pulse sequence with a phase difference of 180 degrees with the uplink pulse sequence and the downlink pulse sequence.

5. The circuit according to claim 4, characterized in that Also includes: an amplifier, whose input end is connected to the knife end of the third single-pole double-throw switch via a resistor, and is used to amplify the downlink ultrasonic signal forwarded by the uplink transducer and the uplink ultrasonic signal forwarded by the downlink transducer; The ADC acquisition module has an input end connected to the output end of the amplifier and an output end connected to the controller, and is used to perform analog-to-digital conversion on the signal output by the amplifier and send the digital signal to the controller.

6. A method for ultrasonically measuring gas flow rate in the circuit according to any one of claims 1 to 5, characterized in that: include: The controller controls the generation of an uplink differential pulse sequence and sends it to the uplink transducer; After receiving the uplink differential pulse sequence, the uplink transducer is excited to generate an uplink ultrasonic signal, while the downlink transducer receives and forwards the uplink ultrasonic signal; amplifying and converting the forwarded uplink ultrasonic signal into digital form, and then sending the signal to the controller; The controller controls the generation of a downlink differential pulse sequence and sends it to the downlink transducer; After receiving the downlink differential pulse sequence, the downlink transducer is excited to generate a downlink ultrasonic signal, and at the same time the uplink transducer receives and forwards the downlink ultrasonic signal; amplifying and converting the forwarded downlink ultrasonic signal into digital form, and then sending the signal to the controller; The controller calculates the corresponding flight time based on the received downlink ultrasonic signal and uplink ultrasonic signal, thereby calculating the actual gas flow rate; The uplink transducer is excited to generate the uplink ultrasonic signal, which is different from the downlink transducer being excited to generate the downlink ultrasonic signal.

7. The circuit according to claim 6, characterized in that The controller controls the generation of an uplink differential pulse sequence and sends it to the uplink transducer, including: The controller controls the generation of an uplink differential pulse sequence, and simultaneously controls the normally closed points of the first single-pole double-throw switch and the second single-pole double-throw switch to be closed, and the first single-pole single-throw switch to be closed, thereby sending the uplink differential pulse sequence to the uplink transducer; The uplink transducer excites and generates an uplink ultrasonic signal, and the downlink transducer receives and forwards the uplink ultrasonic signal, comprising: While the uplink transducer is excited to generate an uplink ultrasonic signal, the controller controls the normally closed points of the third single-pole double-throw switch and the fourth single-pole double-throw switch to be closed and the second single-pole single-throw switch to be disconnected, so that the downlink transducer receives and forwards the uplink ultrasonic signal.

8. The circuit according to claim 6, characterized in that The controller controls the generation of a downlink differential pulse sequence and sends it to the downlink transducer, including: The controller controls the generation of a downstream differential pulse sequence, and simultaneously controls the normally open points of the third single-pole double-throw switch and the fourth single-pole double-throw switch to be closed, and the second single-pole single-throw switch to be closed, thereby sending the downstream differential pulse sequence to the downstream transducer; The downlink transducer excites and generates a downlink ultrasonic signal, and the uplink transducer receives and forwards the downlink ultrasonic signal, comprising: When the downstream transducer is excited to generate a downstream ultrasonic signal, the controller controls the normally open points of the first single-pole double-throw switch and the second single-pole double-throw switch to be closed and the first single-pole single-throw switch to be disconnected, so that the upstream transducer receives and forwards the downstream ultrasonic signal.

9. The circuit according to claim 6, characterized in that The controller controls the generation of an uplink differential pulse sequence including: The controller controls the pulse generator to generate an uplink pulse sequence; The uplink pulse sequence is sent to a driver and an inverter respectively, and an uplink in-phase pulse sequence with enhanced driving capability and a phase difference of 0 degree with the uplink pulse sequence is obtained at the output end of the driver, and an uplink inverted pulse sequence with a phase difference of 180 degrees with the uplink pulse sequence is obtained at the output end of the inverter; The uplink in-phase pulse sequence and the uplink anti-phase pulse sequence together form the uplink differential pulse sequence.

10. The circuit according to claim 6, characterized in that The controller controls the generation of the downlink differential pulse sequence including: The controller controls the pulse generator to generate a downlink pulse sequence; The downlink pulse sequence is sent to a driver and an inverter respectively, and a downlink in-phase pulse sequence with enhanced driving capability and a phase difference of 0 degree with the downlink pulse sequence is obtained at the output end of the driver, and a downlink inverted pulse sequence with a phase difference of 180 degrees with the downlink pulse sequence is obtained at the output end of the inverter; The downlink in-phase pulse sequence and the uplink anti-phase pulse sequence together form the downlink differential pulse sequence.

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