A method for grading ultrasonic transducers for gas metering

Abstract

The present invention relates to a grading method for ultrasonic transducers used for gas metering, belonging to the field of ultrasonic transducer detection technology. First, based on the transducer admittance frequency response obtained by a network analyzer, screening is performed to select transducers with similar admittance parameters and resonant frequencies; according to five grading selection conditions set by a host computer, namely, a signal gain value G, a sampling time length T, a limited range of antinode values, a number of equal divisions m of the sampling time length T, and a corresponding normalized envelope amplitude difference limit of a transducer receiving signal, amplification, filtering and sampling of a received signal within the sampling time length T, ADC, curve fitting of a received signal peak, storage and calculation of received signal envelope amplitude, antinode value, normalized envelope amplitude and normalized envelope amplitude difference, etc., the similarity of the waveform envelope of the transducer receiving signal is judged, and automatic grading is realized. The present invention can ensure that the transducer has better consistency within the used temperature range.

Description

Technical Field

[0001] The invention relates to an ultrasonic transducer grading method for gas metering, belonging to the technical field of ultrasonic transducer detection. Background Art

[0002] Generally, ultrasonic transducers used for gas metering are used in pairs. The accuracy of their flow measurement depends largely on the parameter consistency of the pair of transducers. However, due to certain differences between the two transducers themselves, even after corresponding calibration, the gas flow measurement accuracy will be reduced to a certain extent. In order to reduce the metering error caused by the transducer, it is necessary to select the transducer. The selection method is mainly divided into two categories: pairing and grading. Pairing is selection in pairs; grading is selection according to performance parameters divided into several parameter segments, that is, transducers with similar performance parameters are grouped as one grade. Grading is more conducive to improving the selection and packaging efficiency of transducers and the production efficiency of gas metering equipment.

[0003] Theoretically, there are many grading methods: transducer equivalent concentrated parameter L / C / R grading method, resonant frequency and anti-resonant frequency grading method, impedance parameter grading method, signal envelope amplitude grading method, and static time difference grading method or grading method of corresponding parameter combination.

[0004] The above classification method is feasible in theory, but it is not ideal in practice. To ensure that the transducer has good parameter consistency within the operating temperature range, the key parameter is the similarity of the received signal waveform, that is, when transducer A transmits and B receives or B transmits and A receives, the received ultrasonic signal waveform must have good or good similarity. Summary of the invention

[0005] Because the transducer in the flow meter is used for both transmission and reception, the accuracy of its flow measurement mainly depends on the accuracy and stability of time measurement. Under the premise that the accuracy and stability of the time acquisition module and related hardware are guaranteed, the antinode value of the transducer receiving signal and the envelope shape of the received signal become the key parameters of the transducer.

[0006] In order to solve the above technical problems, the present invention provides an ultrasonic transducer grading method for gas metering, which realizes automatic grading by judging the similarity of the envelope curve of the transducer receiving signal. The technical solution adopted by the present invention is as follows:

[0007] A method for grading an ultrasonic transducer for gas metering comprises the following steps:

[0008] Step 1: In order to make the selected transducer have better consistency in its parameters within the temperature range used, first, based on the transducer admittance frequency response obtained by the network analyzer, a screening is performed to select transducers with similar admittance parameters and resonance frequencies;

[0009] Step 2: According to the signal gain value G, sampling time length T, antinode value limit range Um1-Um2, the number of equal divisions m of the received signal sampling time length T and the corresponding normalized envelope amplitude difference limit of the transducer received signal set by the host computer Five bin selection conditions, implementation of amplification, filtering and sampling of the transducer received signal within the sampling time length T, sampling at the sampling rate determined according to the working frequency of the transducer when the binning device is calibrated, ADC, curve fitting of the received signal peak, envelope amplitude Uqv, antinode value Uantv, and normalized envelope amplitude of the vth received signal corresponding to m equal parts within the sampling time length T and the normalized envelope amplitude difference between the vth and wth fitting curves The calculation and storage of the received signal envelope curves are compared to determine the similarity of the transducer receiving performance and realize the automatic grading function. According to the consistency of the transducer to be selected, the corresponding selection conditions can be appropriately selected to achieve the best grading effect or the required grading effect.

[0010] Beneficial effects of the present invention:

[0011] The present invention first screens according to the transducer admittance frequency response, and then selects according to the similarity of the transducer receiving signal envelope curve through five grading selection conditions, which can ensure that the transducer has better consistency within the used temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a flow chart of an embodiment of the present invention for aligning transducers with the same position number in pairs, implementing the processing of received signals, sampling of received signals and ADC;

[0013] Figure 2 It is a flow chart of an embodiment of the present invention for aligning transducers with different position numbers in pairs, implementing received signal processing, received signal sampling, ADC and peak curve fitting;

[0014] Figure 3 It is a flow chart of determining the antinode value, sampling and normalizing the envelope amplitude, and comparing and grading the envelope curve similarity according to an embodiment of the present invention;

[0015] Figure 4 is a schematic diagram of the overall structure of a transducer grading device according to an embodiment of the present invention;

[0016] Figure 5 is a schematic diagram of the A structure and the B structure of the transducer grading device according to an embodiment of the present invention;

[0017] Figure 6 Schematic diagram of an A rotating motor and a B rotating motor of a transducer stepping device according to an embodiment of the present invention;

[0018] Figure 7 is a block diagram of an electronic module of a transducer grading device according to an embodiment of the present invention;

[0019] In the figure, 1 is A barcode scanner, 2 is B barcode scanner, 3 is A electronic module, 4 is B electronic module, 5 is B rotating motor, 6 is lifting motor, 7 is A structure, 8 is B structure, 9 is sound path tube, and 10 is A rotating motor. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0021] like Figure 1 As shown in FIG. 1 , it is a flow chart of aligning transducers with the same bit number in pairs to implement the processing of received signals, sampling of received signals and ADC in an embodiment of the present invention; Figure 2 As shown in FIG. 1 , it is a flow chart of aligning transducers with different position numbers in pairs, implementing received signal processing, received signal sampling, ADC and peak curve fitting in an embodiment of the present invention; Figure 3 As shown, it is a flow chart of determining the antinode value, sampling and normalizing the envelope amplitude, and comparing and grading the envelope curve similarity according to an embodiment of the present invention. Figure 1 , Figure 2 and Figure 3 The complete process of automatic grading using the transducer grading device of the embodiment of the present invention is constituted, Figure 1 The final step is to Figure 2 The first step, Figure 2 The final step is to Figure 3 The first step. A method for ultrasonic transducer grading for gas metering uses a transducer grading device to judge the similarity of the transducer receiving signal envelope to achieve an automatic grading function, specifically comprising the following steps:

[0022] (1) The host computer starts the code scanning function. A structure 7 and B structure 8 are each equipped with a code scanning gun, which can identify the QR code or barcode on the transducer. The code scanning gun scans the transducers of all positions on the respective structures and stores the transducer position number and serial number. Preferably, n pairs of transducers are symmetrically distributed on the A structure 7 and the B structure 8. The code scanning guns on the A structure 7 and the B structure 8 scan the transducers on the respective structures and store the transducer position number Ai, Bi and transducer serial number, i = 1, 2, 3, ..., n-1, n.

[0023] (2) According to the required transducer consistency, enter the signal gain value G determined by the grading device calibration, the sampling time length T, the antinode value limit range Um1~Um2, the number of equal divisions m of the received signal sampling time length T and the corresponding normalized envelope amplitude difference limit of the transducer received signal in the upper computer dialog box. Five grading selection criteria serve as the basis for grading.

[0024] (3) The transducer grading device aligns two groups of transducers with the same bit number in pairs, that is, Ai transducers are aligned with Bi transducers.

[0025] (4) The host computer sets the gain of the digital control amplifier of the electronic module according to the gain G determined by the calibration of the grading device, and connects the transducer excitation signal source to the Ai transducer, with the Bi transducer as the receiver. The host computer starts the analog signal processing unit of the electronic module, amplifies and filters the signal received by the Bi transducer within the sampling time length T controlled by the host computer, samples the signal at the sampling rate determined according to the operating frequency of the transducer when the grading device is calibrated, performs analog-to-digital conversion through the ADC unit, and then transmits it to the MCU processor for digital filtering, and then transmits it to the host computer. The host computer obtains and stores n groups of data, each group of data reflects the characteristics of the received signal of each transducer, and is data that can reproduce the waveform of the received signal, that is, data that reflects the rate of change of the signal amplitude that changes periodically with time and the peak value that continues to rise and the size of the wave antinode value.

[0026] (5) The host computer starts the electronic module to connect the excitation signal source to the Bi transducer, and the Ai transducer is used as a receiver. The host computer starts the analog signal processing unit of the electronic module, amplifies and filters the signal received by the Ai transducer within the sampling time length T controlled by the host computer, samples it at the same sampling rate as above, performs analog-to-digital conversion through the ADC unit, and then transmits it to the MCU processor for digital filtering, and then transmits it to the host computer. The host computer obtains and stores n groups of data with the same characteristics as step (4). The two groups of transducers with the same bit number in the A structure 7 and the B structure 8 are tested in pairs to obtain and store a total of 2×n groups of data.

[0027] (6) The host computer controls the motor of the grading device to pair the two transducers with different position numbers in sequence, that is, the Aj transducer is paired with the Bk transducer, where j, k = 1, 2, 3, …, n - 1, n, and j ≠ k.

[0028] (7) The host computer starts the electronic module to connect the excitation signal source to the Aj transducer, and the Bk transducer receives. The host computer starts the analog signal processing unit of the electronic module to amplify, filter the signal received by the Bk transducer within the sampling time length T controlled by the host computer, sample at the same sampling rate as above, perform analog-to-digital conversion through the ADC unit, then transmit it to the MCU processor for digital filtering, and then transmit it to the host computer. The host computer obtains and stores n×(n - 1) groups of data with the same characteristics as in step (4).

[0029] (8) The host computer starts the electronic module to connect the excitation signal source to the Bk transducer, and the Aj transducer receives. The signal received by the Aj transducer is amplified, filtered within the sampling time length T controlled by the host computer, sampled at the same sampling rate as above, performed analog-to-digital conversion through the ADC unit, then transmitted to the MCU processor for digital filtering, and then transmitted to the host computer. The host computer obtains and stores n×(n - 1) groups of data with the same characteristics as in step (4).

[0030] (9) The host computer performs peak curve fitting on the 2×n×n groups of data stored in the pairwise alignment tests of the two transducers with the same position numbers and the pairwise alignment tests of the two transducers with different position numbers in the above A structure 7 and B structure 8, obtains 2×n×n envelope curves of the received signals, stores them in the host computer in the form of an array, and names them envelope arrays. Because the envelope curves of the signals received by the designed transducers resemble integral curves, and their envelope amplitudes increase with time within a certain period. Due to the differences between transducer parameters, their envelope amplitude rising rates and maximum values are different, so the envelope amplitudes at the same time are different. When comparing the receiving characteristics of transducers, as long as the envelope amplitude differences or normalized envelope amplitude differences between them are obtained at several identical time points respectively, the similarity of the receiving performances of the two transducers can be judged according to the magnitudes of these envelope amplitude differences or normalized envelope amplitude differences. The sampling time length T is equally divided into m parts according to the equal division number m value of the set sampling time length T, that is, t q = q×T / m, q = 1, 2, 3, …, m, that is, t1 = T / m, t2 = 2×t1, …, tm = m×t1 = T. Only one wave crest appears within the set sampling time length T, and the maximum value of the envelope amplitude is the wave crest value Uant. Uantv represents the wave crest value of the v-th envelope curve. Obtain the signal envelope amplitudes Uqv corresponding to each equal part of each envelope curve within the sampling time length T from the envelope array, where q = 1, 2, 3, …, m, v = 1, 2, 3, …, 2×n×n, and the normalized envelope amplitude Meanwhile, the maximum value of each envelope curve, i.e., the antinode value Uantv of the envelope, is obtained, and 2×m×n×n envelope amplitude data corresponding to m equal parts within the sampling time length T are obtained. The antinode value Uantv and the normalized envelope amplitude are named as the grading array and stored for grading comparison. The larger the value of m, the sampling time equally divided, the finer the division of the envelope curve, and the more delicate the characteristics of the peak fitting curve of the received signal characterized by the envelope amplitude Uqv will be, but the corresponding operation time will be longer.

[0031] (10) The host computer retrieves the antinode value Uantv in the grading array and determines whether all the antinode values Uantv are within the range of Um1 to Um2. The grading of the current round of the transducer corresponding to those not within this range is discarded. For example, if the set Um1 to Um2 is 480 - 500, the antinode values Uantv of the 2×n×n received signal envelopes in the grading data group are retrieved. The grading of the transducer not within the range of 480 - 500 in this round is not considered. If the range requirement is met, the following grading process continues.

[0032] (11) The host computer sequentially calculates the normalized envelope amplitude differences between the received signals of all transducers at the same q That is w > v, and stores its normalized envelope amplitude difference into the grading array established in (9). That is, the grading array contains the antinode value Uantv, the normalized envelope amplitude and the normalized envelope amplitude difference of three types of data. Then it is judged whether it satisfies If it is satisfied, the host computer stores the position numbers, serial numbers and relevant information of all transducers that meet the requirements in this grading; for example, the set That is, retrieve from the grading array, and store the position numbers, serial numbers and relevant information of the transducers that satisfy into the host computer and record it as grade A.

[0033] (12) For the transducers that do not meet Um1 - Um2 or or do not meet both conditions in the above grading operation, the conditions can be appropriately relaxed as needed. For example, relax the range of the envelope antinode value Um1 - Um2, increase the limit value of the normalized envelope amplitude difference value, or relax any one of the two conditions. Retrieve the antinode value Uantv and the normalized envelope amplitude difference of the transducers that did not enter grade A in the first - round grading in the grading array for the second - round grading selection to obtain another grade of transducers. For example, reset Um1 - Um2 to 450 - 480, There is no need to re - conduct the test process. Retrieve the peak value Uantv of the received signal wave of the transducers that did not enter the A - grade in the first - round grading in the grading array and the normalized envelope amplitude difference. Conduct the second - round grading and selection. Some transducers with a slightly lower degree of similarity to the envelope curve of the A - grade can be selected, store their transducer position numbers, serial numbers, and relevant information, and mark them as the B - grade.

[0034] (13) Similarly, for the transducers that did not enter the A - grade and B - grade, the third - round grading and selection can be carried out. Further relax the conditions as needed. For example, set Um1~Um2 to 400~450. Retrieve the peak value Uantv of the received signal wave of the transducers that did not enter the A - grade and B - grade in the first - round and second - round gradings in the grading array and the normalized envelope amplitude difference. Conduct the third - round grading and selection. Another part of the transducers with a slightly lower degree of similarity to the envelope curve of the B - grade can be selected, store their transducer position numbers, serial numbers, and relevant information, and mark them as the C - grade. And so on, until all or part of the transducers are graded as needed.

[0035] In order to implement the ultrasonic transducer grading method for gas metering described above, a transducer grading device is specifically designed in the embodiments of the present invention. The transducer grading device includes: a mechanical structure, an electronic module, and a host computer program module. As Figure 4 shown, it is the overall structural schematic diagram of the transducer grading device in the embodiments of the present invention; as Figure 5 shown, it is the schematic diagram of the A - structure and B - structure of the transducer grading device in the embodiments of the present invention; as Figure 6 shown, it is the schematic diagram of the A - rotation motor and B - rotation motor of the transducer grading device in the embodiments of the present invention.

[0036] First, the transducers screened by the admittance frequency response obtained by the network analyzer are equally divided into two groups. The serial numbers of the transducers in group A are A1~An, and the serial numbers of the transducers in group B are B1~Bn. The transducers in group A and group B are connected by a sound path tube 9 in pairs. The mechanical structure of the transducer grading device is divided into two symmetric structures, which are respectively called the A - structure 7 and the B - structure 8. There are n pairs of transducers symmetrically distributed on the A - structure 7 and the B - structure 8. The serial numbers of the transducers are A1~An and B1~Bn respectively. The transducers on the A - structure 7 and the transducers on the B - structure 8 are connected by a sound path tube 9. Both the A - structure 7 and the B - structure 8 are driven by motors for programmed rotation or lifting, and any two transducers among A1~An and B1~Bn can be aligned pairwise. The motors include: a B - rotation motor 5, a lifting motor 6, and an A - rotation motor 10. An A - code scanner 1 is arranged on one side of the A - structure 7, and a B - code scanner 2 is arranged on one side of the B - structure 8.

[0037] As Figure 7As shown, it is a block diagram of the electronic module of the transducer grading device of an embodiment of the present invention. The electronic module of the transducer grading device consists of an MCU processor, a transducer excitation signal source, an analog switch array, an A1~An and B1~Bn transducer interface, an A1~An and B1~Bn transducer receiving signal channel, an analog signal processing unit, an ADC unit, a motor control unit, a barcode scanning gun interface, a host computer interface and a motor control signal interface. The MCU processor is responsible for the partial control required for transducer grading and the processing of related data. The transducer excitation signal provides a square wave excitation signal according to the operating frequency of the transducer. The analog switch array is controlled by the host computer to realize the switching and transceiver conversion of the transducer. The A1~An and B1~Bn transducer interface is used to connect the A1~An and B1~Bn transducers. The A1~An and B1~Bn transducer receiving signal channel provides a transmission path for the transducer receiving signal. The analog signal processing unit amplifies and filters the signal received by the transducer within the limited sampling time length T. When the transducer grading device is calibrated, the host computer adjusts the amplification factor G of the digital control amplifier of the analog signal processing unit to achieve the required signal antinode value within the limited range Um1~Um2. The G determined by the grading device calibration is entered in the grading process; the ADC unit samples and converts the transducer receiving signal from the analog signal processing unit within the sampling time length T, and transmits it to the MCU processor for digital filtering, and then transmits it to the host computer. The motor control unit implements the rotation or lifting of the relevant motor under the control of the host computer. The barcode scanning gun interface is connected to the barcode scanning gun. The host computer interface is connected to the host computer. The motor control signal interface is connected to the motor. The electronic module includes an A electronic module 3 and a B electronic module 4, and the circuit structures of the A electronic module 3 and the B electronic module 4 are the same.

[0038] The host computer program module of the transducer grading device in the embodiment of the present invention includes: a grading control module, an operation status display module, a grading result display module and a transducer list module. The grading control module is used to control the lifting and rotation of the motor to realize the initial positioning, directional rotation and grading alignment of the transducer grading device, and to set initialization start, initialization stop, pairing start, pairing stop and emergency stop buttons to realize human-computer interaction and facilitate transducer pairing operation.

[0039] In the embodiment of the present invention, (1) n pairs of transducers are symmetrically distributed on the A structure 7 and the B structure 8 of the grading device, and the A structure 7 and the B structure 8 are both controlled by the upper computer to rotate or lift the motor in a program-controlled manner, so that any two transducers A1~An and B1~Bn can be aligned with each other; (2) the signal gain value G, the sampling time length T, the wave antinode value limit range Um1~Um2, the number of equal divisions m of the received signal sampling time length T and the corresponding normalized envelope amplitude difference limit are set Five grading selection conditions are used as the basis for transducer grading; (3) Appropriately select the grading selection conditions according to needs to achieve the best grading effect or different levels of grading effects required; (4) It has the function of arbitrarily aligning two transducers in pairs; (5) It has the functions of amplifying, filtering, timed sampling and ADC for received signals; (6) It has the functions of peak curve fitting and wave belly detection for received signals; (7) It has the functions of equal dividing the sampling time and comparing the envelope amplitudes after equal division; (8) It has the functions of displaying, storing and querying the results and related information of different levels of grading.

[0040] The signal envelope amplitude and signal wave belly value in the present invention, where the amplitude refers to the value of the amplitude, and the belly value is the point with the maximum amplitude. Since the received signal itself is a voltage wave, the wave belly refers to the maximum value of the envelope curve of the received signal voltage wave. The peak value refers to the difference between the maximum or minimum value and its average value within one period of the signal. For a positive and negative symmetric wave, it is the peak value of the wave within one period. Since the signal envelope is a fitting curve of the signal peak value, the maximum (amplitude) value of the signal envelope is the wave belly value. Since the signal received by the transducer vibrates at a certain frequency and the peak value monotonically increases within a certain time for several periods of sine waves, that is, the peak value of the sine wave gradually increases. The curve fitting of the peak value is to perform curve fitting on the peak values of all obtained sine waves, that is, to obtain the fitting curve of the received signal peak value, which is also the received signal envelope curve, simply called the envelope. The envelope curve is a two-dimensional curve, whose abscissa is time and the ordinate is amplitude. What needs to be obtained is the ordinate value of the corresponding point on the envelope curve corresponding to different times, that is, the signal envelope amplitude. The data of its envelope curve contains three information: time, the signal envelope amplitude corresponding to the time, and the signal wave belly value. The array composed of these three information is called the envelope array, which is a data group capable of reproducing the received signal envelope curve.

[0041] The sampling rate of the ADC is determined according to the working frequency of the transducer to be measured and the ADC clock, and is set during system calibration according to the working frequency of the transducer to be graded.

Claims

1. A grading method of ultrasonic transducer for gas metering, It is characterized in that A transducer grading device is designed, which includes: a mechanical structure, an electronic module and a host computer program module; the mechanical structure includes two symmetrical structures, respectively called structure A and structure B, on which n pairs of transducers are symmetrically distributed, and the transducers on structure A and structure B are connected with the transducers on structure B by an acoustic path tube, and both structure A and structure B are driven by a motor to perform program-controlled rotation or lifting; the electronic module is composed of an MCU processor, a transducer excitation signal source, an analog switch array, a transducer interface, a transducer receiving signal channel, an analog signal processing unit, an ADC unit, a motor control unit, a barcode scanner interface, a host computer interface and a motor control signal interface, the MCU processor is responsible for the control and data processing required for transducer grading, the transducer excitation signal source is controlled by the MCU processor to provide a square wave excitation signal according to the operating frequency of the transducer, and the analog signal processing unit performs a sampling time length on the transducer. The signal received within T is amplified and filtered, and the ADC unit samples and performs analog-to-digital conversion on the transducer receiving signal from the analog signal processing unit within the sampling time length T. The ADC unit transmits the data to the MCU processor for digital filtering, and then transmits it to the host computer. The host computer performs curve fitting on the peak value of the data transmitted by the MCU processor to obtain the envelope curve of the transducer receiving signal. The envelope curve is stored in the host computer in the form of an array and is called an envelope array. The host computer divides the sampling time length T into m parts according to the set m value, and obtains the envelope amplitude Uq and wave antinode value Uant corresponding to each part through the envelope array; the host computer program module includes: a grading control module, an operation status display module, a grading result display module and a transducer list module. The grading control module is used to control the lifting and rotation of the motor to realize the initial positioning, directional rotation and grading alignment of the transducer grading device; It includes the following steps: screening based on the transducer admittance frequency response obtained by a network analyzer to select transducers with similar admittance parameters and resonance frequencies; according to the signal gain value G, sampling time length T, the range of peak value limits Um1 to Um2, the number of equal parts m of the sampling time length T, and the limit of the normalized envelope amplitude difference of the received signals of the corresponding transducers Five grading selection conditions are implemented for amplifying, filtering, and sampling the received signal within the sampling time length T, ADC, curve fitting of the peak value of the received signal, the envelope amplitude Uqv of the v-th received signal corresponding to m equal parts within the sampling time length T, the peak value Uantv, and the normalized envelope amplitude And the calculation and storage of the normalized envelope amplitude difference between the v-th and w-th fitting curves The similarity comparison of the received signal envelope curves is performed to judge the similarity of the transducer receiving performance and realize the automatic grading function; specifically, it includes the following steps: (1) The host computer starts the code scanning function. The code scanning guns on the A structure and the B structure scan the transducers on their respective structures and store the transducer position numbers Ai, Bi and transducer numbers, i = 1, 2, 3, ..., n; (2) In the host computer dialog box, enter the signal gain value G, sampling time length T, wave antinode value limit range Um1~Um2, the number of equal divisions of the sampling time length T m and the corresponding normalized envelope amplitude difference limit of the transducer receiving signal Five tier selection criteria; (3) The transducer grading device aligns two groups of transducers with the same position number in pairs; (4) The host computer connects the transducer excitation signal source to the Ai transducer, and the Bi transducer as the receiver, and starts the analog signal processing unit, amplifies, filters, samples, and performs analog-to-digital conversion on the signal received by the Bi transducer within the sampling time length T, and then transmits it to the MCU processor for digital filtering, and then transmits it to the host computer. The host computer obtains and stores n groups of data; (5) The host computer connects the transducer excitation signal source to the Bi transducer, and the Ai transducer as the receiver, and starts the analog signal processing unit, amplifies, filters, samples, and performs analog-to-digital conversion on the signal received by the Ai transducer within the sampling time length T, and then transmits it to the MCU processor for digital filtering, and then transmits it to the host computer, which obtains and stores n groups of data; (6) The host computer controls the motor of the grading device to pair the two transducers with different position numbers in sequence, that is, the Aj transducer is paired with the Bk transducer, where j, k = 1, 2, 3, …, n - 1, n, and j ≠ k; (7) The host computer connects the transducer excitation signal source to the Aj transducer, and the Bk transducer receives it. Then, the analog signal processing unit is started. Within the sampling time length T, the signal received by the Bk transducer is amplified, filtered, sampled, and subjected to analog-to-digital conversion by the ADC unit, and then transmitted to the MCU processor for digital filtering, and then transmitted to the host computer. The host computer obtains and stores n×(n - 1) groups of data; (8) The host computer connects the transducer excitation signal source to the Bk transducer, and the Aj transducer receives it. Then, the analog signal processing unit is started. Within the sampling time length T, the signal received by the Aj transducer is amplified, filtered, sampled, and subjected to analog-to-digital conversion by the ADC unit, and then transmitted to the MCU processor for digital filtering, and then transmitted to the host computer. The host computer obtains and stores n×(n - 1) groups of data; (9) The host computer performs curve fitting on the peaks of the 2×n×n groups of data stored in the pairwise alignment tests of the two transducers with the same serial numbers and the pairwise alignment tests of the two transducers with different serial numbers in the above A structure and B structure, obtains 2×n×n envelope curves of the received signals, stores them in the host computer in the form of an array, and names them envelope arrays; according to the number m of equal parts of the sampling time length T, the sampling time length T is equally divided into m parts, that is, t q =q×T / m, q = 1, 2, 3, …, m, that is, t1 = T / m, t2 = 2×t1, …, tm = T. Only one wave belly appears within the set sampling time length T, and the maximum value of the envelope amplitude is the wave belly value Uant. Uantv represents the wave belly value of the v-th envelope curve; obtain the signal envelope amplitude Uqv corresponding to each equal part of each envelope curve within the sampling time length T from the envelope array, q = 1, 2, 3, …, m, v = 1, 2, 3, …, 2×n×n, and the normalized envelope amplitude At the same time, the wave belly value Uantv of each envelope curve is obtained, and the normalized envelope amplitudes corresponding to m equal parts within the sampling time length T are obtained There are a total of 2×m×n×n. Name the wave belly value Uantv and the normalized envelope amplitude as the grading array and store it for grading comparison; (10) The host computer retrieves the antinode value Uantv in the grading array and determines whether all the antinode values Uantv are within the range of Um1 to Um2. The transducers that are not within this range are discarded in this round of grading. If the range requirements are met, the following grading process continues; (11) The host computer sequentially calculates the normalized envelope amplitude differences between the received signals of all transducers at the same q That is Take its normalized envelope amplitude difference Store it in the binning array established in step (9), and then judge whether it satisfies If it is satisfied, the host computer stores the position numbers, serial numbers and relevant information of all transducers that meet the requirements in this binning, and records them as Class A; (12) For those who do not meet the requirements of Um1~Um2 or For transducers that do not meet both conditions, relax the conditions as needed and retrieve the antinode value Uantv and the normalized envelope amplitude difference in the bin array. Carry out the second round of bin selection, store the transducer position number, serial number and related information, and record it as B bin; (13) Similarly, for the transducers that did not enter the B grade, a third round of grading and selection is carried out. The peak value Uantv of the received signal wave of the transducers that did not enter grades A and B in the first and second rounds of grading in the grading array is retrieved, as well as the normalized envelope amplitude difference. A third round of grading and selection is carried out, and the transducer serial number, number, and related information are stored and recorded as grade C.

2. A method for grading ultrasonic transducers for gas metering according to claim 1, wherein, The host computer program module sets the initialization start, initialization stop, pairing start, pairing stop, and emergency stop buttons.

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