Ultrasonic gas meter and method for gas composition analysis

Abstract

This application provides an ultrasonic gas meter, which includes a transmitting transducer, a receiving transducer, and a processing module. The processing module calculates the propagation speed of the ultrasonic signal and generates an echo signal based on the ultrasonic signal received by the receiving transducer. The ultrasonic gas meter also includes an environmental information detection module for acquiring environmental information about the environment in which the ultrasonic gas meter is located; a gain self-adjustment module for amplifying the echo signal to a preset voltage range and calculating the signal gain; the processing module stores the trend of ultrasonic propagation speed changing with environmental information under certain conditions; the processing module determines whether the change in ultrasonic propagation speed conforms to the trend based on the changes in ultrasonic propagation speed and environmental information over a period of time; if so, the processing module determines whether the gas quality in the pipeline has changed based on the change in signal gain over the time period. The ultrasonic gas meter provided by this application provides more accurate judgment of gas quality changes.

Description

Technical Field

[0001] This application relates to the field of gas monitoring technology, and in particular to an ultrasonic gas meter and a gas composition analysis method. Background Technology

[0002] Ultrasonic gas meters use the time-of-flight method as their metering principle. By detecting flight time and combining it with structural parameters and environmental variables, they obtain the instantaneous flow rate. For example... Figure 1 As shown, in the time-of-flight detection, the transmitting transducer is excited by the circuit system to generate vibration. The vibration is transmitted to the receiving transducer through the gas medium. The receiving transducer converts the mechanical vibration into an electrical signal. This signal is amplified and filtered by the circuit to obtain an effective echo signal.

[0003] In related technologies, the speed of sound can be used to determine the current atmospheric characteristics. However, the speed of sound is affected by current flow rate, temperature, and pressure, leading to inaccurate judgments and extremely granular results. Summary of the Invention

[0004] The purpose of this application is to provide a technical solution to solve the problem in related technologies where judging gas quality solely based on ultrasonic velocity is inaccurate due to the influence of current flow rate, temperature, and pressure.

[0005] To achieve the above objectives, this application provides an ultrasonic gas meter, comprising: a transmitting transducer, a receiving transducer, and a processing module. The transmitting transducer transmits ultrasonic signals; the receiving transducer is positioned at a preset distance from the transmitting transducer and receives the ultrasonic signals; the processing module detects the time of flight of the ultrasonic signals, calculates the propagation speed of the ultrasonic signals based on the time of flight and the preset distance, and generates an echo signal based on the ultrasonic signals received by the receiving transducer. The ultrasonic gas meter also includes:

[0006] The environmental information detection module is used to acquire environmental information about the environment in which the ultrasonic gas meter is located.

[0007] The gain self-adjustment module is used to amplify the echo signal to a preset voltage range and calculate the signal gain.

[0008] The processing module stores the trend of ultrasonic wave propagation speed changing with environmental information under certain conditions;

[0009] The processing module determines whether the change in ultrasonic propagation speed conforms to the trend based on the changes in ultrasonic propagation speed and environmental information over a period of time. If so, the processing module determines whether the gas quality inside the pipe has changed based on the changes in signal gain over the time period.

[0010] Furthermore, the environmental information detection module includes a temperature detection unit, which is used to detect temperature data. The environmental information includes temperature data, and the trend of change includes the first trend of change of ultrasonic wave propagation speed with temperature under certain pressure and constant gas quality conditions.

[0011] The processing module obtains the changes in ultrasonic propagation speed and temperature based on ultrasonic propagation speed data and temperature data over a period of time. The processing module determines whether the changes in ultrasonic propagation speed and temperature conform to the first trend. If so, the processing module determines whether the signal gain has changed within the time period. If the signal gain has changed, the processing module determines that the gas quality inside the pipe has changed.

[0012] Furthermore, the environmental information detection module also includes a pressure detection unit, which is used to detect pressure data. The environmental information also includes pressure data, and the trend of change also includes a second trend of the change of ultrasonic wave propagation speed with pressure under certain temperature and constant gas quality conditions.

[0013] In response to the determination that the changes in ultrasonic wave propagation speed and temperature do not conform to the first trend, the processing module determines whether the changes in ultrasonic wave propagation speed and pressure conform to the second trend. If they conform to the second trend, the processing module determines whether the signal gain changes within a certain time period. If the signal gain changes, the processing module determines that the gas quality inside the pipe has changed. The pressure change is obtained based on the pressure data over a certain period of time.

[0014] Furthermore, in response to the determination that the changes in ultrasonic propagation speed and temperature do not conform to the first trend, and that the changes in ultrasonic propagation speed and pressure do not conform to the second trend, the processing module determines whether the signal gain changes within a certain time. If the signal gain changes, the processing module determines that the gas quality inside the pipe has changed; otherwise, the processing module determines that the detection is abnormal.

[0015] Furthermore, in response to detecting a decrease in pressure and a change in signal gain, the processing module determines that a leak has occurred in the pipeline.

[0016] Furthermore, the sampling frequency of the temperature detection unit is lower than that of the pressure detection unit, and the sampling frequency of the temperature detection unit is lower than that of the gain self-adjustment module for recording signal gain.

[0017] Furthermore, in response to the determination that the changes in ultrasonic propagation speed and temperature do not conform to the first trend, the processing module sends control signals to the transmitting transducer and the receiving transducer to increase the sampling frequency of the ultrasonic signal flight time.

[0018] Furthermore, the processing module is connected to the gain self-adjustment module to receive signal gain data over a period of time. The processing module calculates the gain range based on the signal gain data and compares the gain range with a preset gain threshold. If the gain range is greater than the preset gain threshold, the processing module determines that the signal gain has changed.

[0019] This application also provides a gas composition analysis method applied to an ultrasonic gas meter, the ultrasonic gas meter comprising:

[0020] Transmitting transducer, used to transmit ultrasonic signals;

[0021] A receiving transducer is positioned at a preset distance from the transmitting transducer and is used to receive ultrasonic signals.

[0022] The processing module is used to detect the flight time of the ultrasonic signal, calculate the propagation speed of the ultrasonic signal based on the flight time and preset distance, and generate an echo signal based on the ultrasonic signal received by the receiving transducer.

[0023] Further methods for gas composition analysis include:

[0024] Obtain environmental information about the location of the ultrasonic gas meter;

[0025] The echo signal is amplified to a preset voltage range, and the signal gain is calculated.

[0026] Generate the trend of ultrasonic wave propagation speed changing with environmental information under certain conditions;

[0027] Based on the changes in ultrasonic wave propagation speed and environmental information over a period of time, determine whether the changes in ultrasonic wave propagation speed conform to the trend. If so, determine whether the gas composition inside the pipe has changed based on the changes in signal gain over the time period.

[0028] Furthermore, the environmental information includes temperature data, and the trend of change includes the first trend of change of ultrasonic wave propagation speed with temperature under certain pressure and constant atmospheric conditions.

[0029] The method also includes: obtaining changes in ultrasonic propagation speed and temperature based on ultrasonic propagation speed data and temperature data over a period of time; determining whether the changes in ultrasonic propagation speed and temperature conform to a first trend; if so, determining whether the signal gain changes over the time period; if the signal gain changes, the processing module determines that the gas quality inside the pipe has changed.

[0030] In summary, the ultrasonic gas meter provided in this application determines whether the gas quality in the pipeline has changed by combining changes in ultrasonic propagation speed with environmental information and changes in signal gain. This can solve the problem in related technologies where the gas quality is inaccurate when judging solely based on ultrasonic speed due to the influence of current flow rate, temperature, and pressure. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the signal transmission and reception principle of an ultrasonic gas meter in related technologies.

[0032] Figure 2 This is a schematic diagram of ultrasonic gas representation provided in the embodiments of this application.

[0033] Figure 3 This is a schematic diagram of the environmental information detection module provided in an embodiment of this application.

[0034] Figure 4 This is a flowchart of a gas composition analysis method provided in an embodiment of this application. Detailed Implementation

[0035] The present application will be described in detail below with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present application. Any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the protection scope of the present application.

[0036] like Figure 2 As shown in the illustration, this application provides an ultrasonic gas meter, which includes a transmitting transducer, a receiving transducer, a processing module, an environmental information detection module, and a gain self-adjustment module. The transmitting transducer transmits ultrasonic signals. The receiving transducer is positioned at a preset distance from the transmitting transducer and receives the ultrasonic signals. The processing module detects the time-of-flight of the ultrasonic signals, calculates the propagation speed of the ultrasonic signals based on the time-of-flight and the preset distance, and generates an echo signal based on the ultrasonic signals received by the receiving transducer.

[0037] The environmental information detection module is used to acquire environmental information about the environment in which the ultrasonic gas meter is located. The gain self-adjustment module is used to amplify the echo signal to a preset voltage range and calculate the signal gain.

[0038] The processing module stores the trend of ultrasonic wave propagation speed changing with environmental information under certain conditions. Based on the changes in ultrasonic wave propagation speed and environmental information over a period of time, the processing module determines whether the change in ultrasonic wave propagation speed conforms to the trend. If so, the processing module determines whether the gas quality inside the pipe has changed based on the change in signal gain over the time period.

[0039] Specifically, the propagation speed of ultrasound is easily affected by environmental factors such as temperature and pressure. The ultrasonic gas meter provided in this application embodiment stores the trend of the ultrasonic propagation speed changing with environmental information under certain conditions. If the change in the ultrasonic propagation speed is detected to match the trend, it can be determined that the ultrasonic propagation speed is affected by environmental changes. At this time, it is not possible to determine whether the gas quality in the gas pipeline has changed based solely on the change in the speed of sound of ultrasound. Therefore, the ultrasonic gas meter provided in this application embodiment further determines whether the gas quality in the pipeline has changed based on the change in signal gain.

[0040] Specifically, the ultrasonic gas meter provided in this application detects whether the signal gain changes when the change in ultrasonic propagation speed conforms to a changing trend. If the signal gain changes, it can be determined that the gas quality has changed; if the signal gain does not change, it can be determined that the gas quality has not changed.

[0041] It should be noted that signal gain is an actively controlled quantity, the purpose of which is to amplify the echo signal to a preset voltage range. However, ultrasound waves attenuate to varying degrees in different atmospheres, therefore the required signal gain also differs in different atmospheres. Thus, whether the signal gain changes can be used as an indicator to identify whether the atmosphere changes.

[0042] To further illustrate the feasibility of using signal gain change as an indicator of whether gas quality has changed, this application example selects five types of test gas from Appendix A of the national standard GB / T 39841-2021 "Ultrasonic Gas Meters" based on sound velocity, attenuation, viscosity, and density to evaluate the meter's characteristics. Real-world natural gas is more complex, but most of its physical properties fall between these five test gas types. See Table 1 for details.

[0043] Serial Number Gas Name Speed ​​of sound signal amplitude Gain 1 Air maximum maximum Minimum 2 100% methane Minimum medium medium 3 94% methane, 6% carbon dioxide medium smaller Larger 4 70% methane, 30% ethane medium medium medium 5 89% methane, 11% hydrogen smaller smaller Larger

[0044] Table 1

[0045] It should be noted that the comparisons of sound velocity and signal strength for the different gases mentioned above were obtained under normal temperature and pressure testing conditions. As shown in Table 1, based on theoretical calculations and actual tests, the sound velocity and signal characteristics of the five gases differ under normal temperature and pressure. Among them, air and natural gas are highly distinguishable, and there are also some differences among the other gases. Combining sound velocity, signal gain, and environmental variables, most gas switching scenarios can be detected.

[0046] like Figure 3As shown, as an optional implementation, the environmental information detection module includes a temperature detection unit for detecting temperature data. The environmental information includes temperature data, and the trend of change includes a first trend of ultrasonic wave propagation speed change with temperature under certain pressure and constant gas quality conditions. The processing module obtains the ultrasonic wave propagation speed change and temperature change based on the ultrasonic wave propagation speed data and temperature data over a period of time. The processing module determines whether the ultrasonic wave propagation speed change and temperature change conform to the first trend of change. If so, the processing module determines whether the signal gain has changed within the time period. If the signal gain has changed, the processing module determines that the gas quality inside the pipe has changed.

[0047] Specifically, according to the formula for calculating the speed of sound In the formula, c represents the speed of sound, λ is the ratio of isobaric specific heat to isochoric specific heat; R is the gas constant; T is the temperature; and M is the relative molecular mass of the gas. It can be seen that under certain pressure and constant gaseous conditions, the propagation speed of ultrasound is positively correlated with temperature; that is, the propagation speed of ultrasound increases with increasing temperature and decreases with decreasing temperature. Therefore, when an increase in the propagation speed of ultrasound and an increase in temperature are detected, it can be determined that the changes in the propagation speed and temperature conform to physical characteristics, and further determination of whether the gaseous state has changed is needed using signal gain. When the signal gain also changes, it can be determined that the current gaseous state has changed; if the signal gain does not change, it can be determined that the change in the current propagation speed of ultrasound is caused by a temperature change.

[0048] As an optional implementation, the environmental information detection module also includes a pressure detection unit, which is used to detect pressure data. The environmental information also includes pressure data, and the change trend also includes a second change trend of the ultrasonic wave propagation speed changing with pressure under certain temperature and constant gas quality conditions.

[0049] In response to the determination that the changes in ultrasonic wave propagation speed and temperature do not conform to the first trend, the processing module determines whether the changes in ultrasonic wave propagation speed and pressure conform to the second trend. If they conform to the second trend, the processing module determines whether the signal gain changes within a certain time period. If the signal gain changes, the processing module determines that the gas quality inside the pipe has changed. The pressure change is obtained based on the pressure data over a certain period of time.

[0050] Specifically, according to the sound velocity calculation formula, under a certain temperature and constant gas quality, the change in ultrasonic wave propagation speed is positively correlated with the pressure change. Therefore, the second trend is that the change in ultrasonic wave propagation speed is positively correlated with the pressure change. If the change in ultrasonic wave propagation speed and temperature do not conform to the first trend, but the change in ultrasonic wave propagation speed and pressure conform to the second trend, then the change in ultrasonic wave propagation speed may be caused by pressure. In this case, the change in gas quality cannot be determined solely based on the change in ultrasonic wave propagation speed. To address this, the ultrasonic gas meter provided in this application further determines whether the gas quality in the pipeline has changed based on signal gain. That is, if the signal gain does not change, it is determined that the gas quality has not changed; if the signal gain changes, it is determined that the gas quality has changed.

[0051] As an optional implementation, in response to the determination that changes in ultrasonic propagation speed and temperature do not conform to a first trend, and changes in ultrasonic propagation speed and pressure do not conform to a second trend, the processing module determines whether the signal gain has changed. If the signal gain changes, the processing module determines that the gas composition within the pipe has changed; otherwise, the processing module determines that a detection anomaly has occurred. It is easy to understand that, according to the sound velocity calculation formula, ultrasonic propagation speed is affected by factors such as gas composition, temperature, and pressure. If the change in ultrasonic propagation speed does not conform to the first trend with temperature and the second trend with pressure, and the signal gain remains unchanged, then the changes in ultrasonic propagation speed and its related influencing factors do not conform to physical characteristics. Therefore, a detection anomaly can be determined. A detection anomaly can be caused by one or more of the following detection items: temperature detection, pressure detection, and signal gain detection.

[0052] As an optional implementation, the processing module determines that a leak has occurred in the pipeline if it determines that the changes in ultrasonic propagation speed and temperature do not conform to a first trend, the changes in ultrasonic propagation speed and pressure do not conform to a second trend, and it detects a decrease in pipeline pressure and a change in signal gain.

[0053] It is easy to understand that when a pipeline leaks, the pipeline pressure decreases, and air will mix into the pipeline, causing a change in the gas quality. The ultrasonic gas meter provided in this application can distinguish between gas quality changes caused by gas switching and gas quality changes caused by gas leaks, and can issue an alarm for gas quality changes caused by gas leaks to prevent safety accidents.

[0054] It should be noted that the judgments regarding the first trend, the second trend, and the signal gain are not in any particular order. The analysis results can be obtained by referring to the preset processing analysis table based on the results of each judgment item. The processing analysis table includes the analysis results and processing operations corresponding to different combinations of judgment item results. Specifically, as shown in Table 2:

[0055]

[0056]

[0057] Table 2

[0058] As shown in Table 2, in this embodiment, the first step is to detect whether the changes in ultrasonic wave propagation speed and temperature conform to a first trend. If they do, the gaseous quality change can be temporarily disregarded, and the signal gain can be detected at the normal operating sampling frequency. If the signal gain changes, vigilance should be maintained regarding gaseous quality switching. If the changes in ultrasonic wave propagation speed and temperature do not conform to the first trend, the sampling frequency can be increased to detect whether the signal gain changes, and pressure changes can also be detected. Based on the results of each judgment item and referring to Table 2, the corresponding analysis and processing operations can be obtained.

[0059] As an optional implementation, in this embodiment, the determination of ultrasonic propagation speed, temperature, pressure, and signal gain changes is obtained through multiple sampling analyses, thereby avoiding interference from sporadic data and improving the accuracy of the determination results. The ultrasonic gas meter can store a preset capacity of data. Following a first-in, first-out (FIFO) principle, when the amount of data collected by the ultrasonic gas meter exceeds the preset capacity, the oldest data is discarded, and newly collected data is added to complete the data update. Based on the data collected by the ultrasonic gas meter, analysis of ultrasonic propagation speed, temperature, pressure, and signal gain changes can be performed.

[0060] Specifically, the determination of changes in the speed of ultrasonic wave propagation is as follows:

[0061] The ultrasonic gas meter stores the most recent 2*m1 sound velocity values ​​and calculates the range ΔC of these sound velocities. If ΔC ≥ ΔC', then the sound velocity is considered to be potentially variable.

[0062] The average of the first m1 sound velocity values ​​is calculated as C1, and the average of the last m1 sound velocity values ​​is calculated as C2. If C1-C2>C", the sound velocity is considered to have decreased; if C2-C1>C", the sound velocity is considered to have increased; otherwise, the change in sound velocity is considered to be insignificant. ΔC' and C" are set according to actual needs and can be obtained through statistical analysis of experimental data.

[0063] The determination of signal gain change is as follows:

[0064] The processing module calculates the gain range value based on the signal gain data. The processing module compares the gain range value with a preset gain threshold. If the gain range value is greater than the preset gain threshold, the processing module determines that the signal gain has changed.

[0065] Specifically, the ultrasonic gas meter stores the gain values ​​of the most recent 2*m² signals, calculates the range of these gain values, and obtains the gain range value ΔG. If the gain range value ΔG is greater than the preset gain threshold ΔG', that is, if ΔG≥ΔG' is satisfied, then the gain is considered to have changed.

[0066] The average of the first m² gain values ​​is calculated as G1, and the average of the last m² gain values ​​is calculated as G2. If G1 - G2 > G", the gain is considered to have decreased; if G2 - G1 > G", the gain is considered to have increased; otherwise, the gain change is considered to be insignificant. ΔG' and G” are set according to actual needs and can be obtained through statistical analysis of experimental data.

[0067] The judgment of pressure changes is as follows:

[0068] The ultrasonic gas meter stores the most recent 2*m³ pressure values ​​and calculates the range ΔP of these pressures. If ΔP ≥ ΔP', the pressure is considered to be potentially variable.

[0069] The average of the first m3 pressure values ​​is calculated as P1, and the average of the last m3 pressure values ​​is calculated as P2. If P1 - P2 > P", the pressure is considered to have decreased; if P2 - P1 > P", the pressure is considered to have increased; otherwise, the pressure change is considered to be insignificant. ΔP' and P" are set according to actual needs and can be obtained through statistical analysis of experimental data.

[0070] The judgment regarding temperature changes is as follows:

[0071] The ultrasonic gas meter stores the most recent 2*m4 temperature values ​​and calculates the range ΔTMP of these temperatures. If ΔTMP ≥ Δtmp', the temperature is considered to be possibly changing.

[0072] The average of the first m4 temperature values ​​is calculated as TMP1, and the average of the last m4 temperature values ​​is calculated as TMP2. If TMP1 - TMP2 > tmp", the temperature is considered to have decreased; if TMP2 - TMP1 > tmp", the temperature is considered to have increased; otherwise, the temperature change is considered to be insignificant. The values ​​Δtmp' and tmp can be set according to actual needs and can be obtained through statistical analysis of experimental data.

[0073] As an optional implementation, the amount of sound velocity data, signal gain data, pressure data, and temperature data stored in the ultrasonic gas meter can be the same or different.

[0074] As an optional implementation, in this embodiment, the sampling frequency of the temperature detection unit is lower than that of the pressure detection unit, and also lower than the sampling frequency of the gain self-adjustment module for recording signal gain. This approach minimizes the power consumption of the ultrasonic gas meter and enhances its battery life. Furthermore, in practical applications, temperature changes relatively slowly compared to pressure; reducing the temperature sampling frequency still ensures the accuracy of the gas quality detection results from the ultrasonic gas meter.

[0075] As an optional implementation, in response to the determination that changes in ultrasonic propagation speed and temperature do not conform to a first trend, the processing module sends control signals to the transmitting and receiving transducers to increase the sampling frequency of the ultrasonic signal's time-of-flight. Specifically, under normal operating conditions, the ultrasonic gas meter collects the ultrasonic propagation speed at a first sampling frequency. When the processing module determines that changes in ultrasonic propagation speed and temperature do not conform to the first trend, the ultrasonic gas meter collects the ultrasonic propagation speed at a second sampling frequency, where the first sampling frequency is lower than the second sampling frequency. In this way, the metering accuracy can be improved when detecting gas quality changes, and the power consumption of the ultrasonic gas meter can be reduced in daily operation, thus enhancing its battery life.

[0076] like Figure 4 As shown in the illustration, this application also provides a gas composition analysis method applied to an ultrasonic gas meter. The ultrasonic gas meter includes a transmitting transducer, a receiving transducer, and a processing module. The transmitting transducer is used to transmit ultrasonic signals; the receiving transducer is located at a preset distance from the transmitting transducer and is used to receive ultrasonic signals; the processing module is used to detect the flight time of the ultrasonic signals, calculate the propagation speed of the ultrasonic signals based on the flight time and the preset distance, and generate an echo signal based on the ultrasonic signals received by the receiving transducer.

[0077] Gas composition analysis methods include the following steps:

[0078] Step S1: Obtain environmental information of the environment where the ultrasonic gas meter is located;

[0079] Step S2: Amplify the echo signal to a preset voltage range and calculate the signal gain;

[0080] Step S3: Generate the trend of ultrasonic wave propagation speed changing with environmental information under certain conditions;

[0081] Step S4: Based on the changes in ultrasonic propagation speed and environmental information over a period of time, determine whether the changes in ultrasonic propagation speed conform to the trend. If so, determine whether the gas quality inside the pipe has changed based on the changes in signal gain over the time period.

[0082] As an optional implementation, the environmental information includes temperature data, and the trend of change includes a first trend of change in ultrasonic wave propagation speed with temperature change under certain pressure and constant gas quality conditions. The gas composition analysis method provided in this application embodiment further includes: obtaining the changes in ultrasonic wave propagation speed and temperature based on ultrasonic wave propagation speed data and temperature data over a period of time; determining whether the changes in ultrasonic wave propagation speed and temperature conform to the first trend of change; if so, determining whether the signal gain changes during the time period; if the signal gain changes, the processing module determines that the gas quality inside the pipeline has changed.

[0083] The above-disclosed embodiments are merely preferred embodiments of this application, but are not intended to limit the scope of this application. Those skilled in the art will understand that any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and scope of this application and the appended claims are equivalent substitutions and still fall within the scope of the invention.

Claims

1. An ultrasonic gas meter, the ultrasonic gas meter comprising: A transmitting transducer for transmitting ultrasonic signals; A receiving transducer is provided, wherein the receiving transducer is located at a predetermined distance from the transmitting transducer, and the receiving transducer is used to receive the ultrasonic signal. The processing module is used to detect the flight time of the ultrasonic signal, calculate the propagation speed of the ultrasonic signal based on the flight time and the preset distance, and generate an echo signal based on the ultrasonic signal received by the receiving transducer. The ultrasonic gas meter is characterized in that it further includes: An environmental information detection module is used to acquire environmental information about the environment in which the ultrasonic gas meter is located. A gain self-adjustment module is used to amplify the echo signal to a preset voltage range and calculate the signal gain; The processing module stores the trend of ultrasonic wave propagation speed changing with environmental information under certain conditions. The processing module determines whether the change in ultrasonic propagation speed conforms to the trend based on the change in ultrasonic propagation speed and the change in environmental information over a period of time. If so, the processing module determines whether the gas quality in the pipe has changed based on the change in signal gain over the time period. The environmental information detection module includes a temperature detection unit, which is used to detect temperature data. The environmental information includes the temperature data, and the trend of change includes a first trend of change of ultrasonic wave propagation speed with temperature under certain pressure and constant gas quality. The processing module obtains the changes in ultrasonic propagation speed and temperature based on ultrasonic propagation speed data and temperature data over a period of time. The processing module determines whether the changes in ultrasonic propagation speed and temperature conform to the first change trend. If so, the processing module determines whether the signal gain changes within the time period. If the signal gain changes, the processing module determines that the gas quality inside the pipe has changed. The environmental information detection module also includes a pressure detection unit, which is used to detect pressure data. The environmental information also includes the pressure data. The trend of change also includes a second trend of the change of ultrasonic wave propagation speed with pressure under certain temperature and constant gas quality conditions. In response to determining that the change in ultrasonic wave propagation speed and the change in temperature do not conform to the first trend, the processing module determines whether the change in ultrasonic wave propagation speed and the change in pressure conform to the second trend. If they conform to the second trend, the processing module determines whether the signal gain changes within the time period. If the signal gain changes, the processing module determines that the gas quality inside the pipe changes. The pressure change is obtained based on the pressure data over a period of time. The processing module is connected to the gain self-adjustment module to receive signal gain data over a period of time. The processing module calculates a gain range value based on the signal gain data and compares the gain range value with a preset gain threshold. If the gain range value is greater than the preset gain threshold, the processing module determines that the signal gain has changed.

2. The ultrasonic gas meter according to claim 1, characterized in that, In response to determining that the changes in ultrasonic wave propagation speed and temperature do not conform to the first trend, and that the changes in ultrasonic wave propagation speed and pressure do not conform to the second trend, the processing module determines whether the signal gain changes within the time period. If the signal gain changes, the processing module determines that the gas quality inside the pipe has changed; otherwise, the processing module determines that a detection anomaly has occurred.

3. The ultrasonic gas meter according to claim 2, characterized in that, In response to detecting a decrease in pressure and a change in signal gain, the processing module determines that a leak has occurred in the pipeline.

4. The ultrasonic gas meter according to claim 1, characterized in that, The sampling frequency of the temperature detection unit is lower than that of the pressure detection unit, and the sampling frequency of the temperature detection unit is lower than that of the sampling frequency of the gain self-adjustment module for recording signal gain.

5. The ultrasonic gas meter according to claim 4, characterized in that, In response to determining that the changes in ultrasonic wave propagation speed and temperature do not conform to the first trend, the processing module sends control signals to the transmitting transducer and the receiving transducer to increase the sampling frequency of the ultrasonic wave signal flight time.

6. A gas composition analysis method, applied to the ultrasonic gas meter according to any one of claims 1 to 5, wherein the ultrasonic gas meter comprises: A transmitting transducer for transmitting ultrasonic signals; A receiving transducer is provided, wherein the receiving transducer is located at a predetermined distance from the transmitting transducer, and the receiving transducer is used to receive the ultrasonic signal. The processing module is used to detect the flight time of the ultrasonic signal, calculate the propagation speed of the ultrasonic signal based on the flight time and the preset distance, and generate an echo signal based on the ultrasonic signal received by the receiving transducer. The gas composition analysis method is characterized by comprising: Obtain environmental information about the environment where the ultrasonic gas meter is located; The echo signal is amplified to a preset voltage range, and the signal gain is calculated; Generate the trend of ultrasonic wave propagation speed changing with the environmental information under certain conditions; Based on the changes in ultrasonic wave propagation speed and environmental information over a period of time, it is determined whether the changes in ultrasonic wave propagation speed conform to the trend of change. If so, it is determined whether the gas quality inside the pipe has changed based on the changes in signal gain over the time period.

7. The gas composition analysis method according to claim 6, characterized in that, The environmental information includes temperature data, and the trend of change includes a first trend of change in ultrasonic wave propagation speed with temperature under certain pressure and constant atmospheric conditions. The method further includes: obtaining changes in ultrasonic propagation speed and temperature based on ultrasonic propagation speed data and temperature data over a period of time; determining whether the changes in ultrasonic propagation speed and temperature conform to the first change trend; if so, determining whether the signal gain changes during the time period; if the signal gain changes, the processing module determines that the gas quality inside the pipe has changed.

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