A seismic data acquisition system and precision correction method

Abstract

The application belongs to the field of seismic exploration and discloses a seismic data acquisition system and a precision correction method.The system comprises a central control unit, a GPS module and an ADC module.The central control unit acquires the PPS signal of the GPS module, triggers the acquisition task at the rising edge of the PPS signal, and reads the output data of the ADC module when detecting that the DRDY pin output signal of the ADC module is a falling edge.The temperature-compensated crystal oscillator is used to provide a sampling time reference for the ADC module.The central control unit calculates the error of the temperature-compensated crystal oscillator according to the DRDY signal of the ADC module and the PPS signal of the GPS module, calculates a correction value according to the error, and adjusts the sampling frequency of the ADC module according to the correction value.The application can estimate the deviation of the temperature-compensated crystal oscillator in real time, realize frequency error measurement and dynamic compensation by adjusting the sampling frequency of the ADC module, enhance the time-frequency stability of the seismic data acquisition system, and be used for high-precision seismic monitoring.

Description

Technical Field

[0001] This application belongs to the field of seismic exploration, specifically a seismic data acquisition system and an accuracy correction method. Background Technology

[0002] Modern earthquake monitoring instruments widely employ high-precision analog-to-digital converters to obtain detailed information about earthquake waveforms. This high-resolution, high-speed acquisition mode results in a massive amount of raw data, thus placing higher demands on time synchronization. Insufficient time synchronization performance will severely affect the accurate alignment of earthquake signals, leading to significant errors in data analysis and rendering the acquisition results worthless.

[0003] To achieve low power consumption in the seismic data acquisition system, dynamic power management technology is employed after successful GPS timing synchronization. Within the acquisition station, the processor module controls the power management module to shut down the GPS module. The seismic data acquisition system uses a temperature-compensated crystal oscillator (TCSO) to provide time service. However, the TSO is temperature-sensitive, and its frequency shifts with temperature changes. Fieldwork involves long-term operations, and the accumulated frequency drift leads to significant cumulative errors. When the maximum allowable error for the synchronization system (one sampling interval) is reached, the processor module manages the power supply to the functional modules, activating the GPS module to precisely correct the accumulated error of the TSO. While this reduces power consumption to some extent, the characteristics of the TSO necessitate continuous activation of the GPS module for correction over a certain period, thus failing to achieve maximum power reduction.

[0004] As acquisition time increases, frequency drift of the crystal oscillator at the acquisition station leads to significant accumulation of time errors, necessitating error compensation or correction capabilities in the time synchronization system. Currently, temperature-compensated crystal oscillators (TCS) are widely used in seismic data acquisition systems as local frequency references. However, the accuracy of existing TCSs typically relies on external frequency measurement instruments and requires continuous operation of the GPS module for frequency compensation, resulting in high cost, complex structure, and unsuitability for embedded or resource-constrained scenarios. Although the PPS signal (one pulse per second) from the GPS module provides a second-level time reference, seismic data acquisition systems still struggle to directly and accurately measure the deviation of the TCS. Summary of the Invention

[0005] This application provides an earthquake data acquisition system that addresses the problem of insufficient time synchronization performance in data acquisition, which affects the accurate alignment of earthquake signals.

[0006] This application also provides a method for accuracy correction of an earthquake data acquisition system.

[0007] An earthquake data acquisition system according to a first aspect of this application includes:

[0008] The central control unit acquires the PPS signal from the GPS module and connects it to the DRDY pin of the ADC module via an interrupt pin. It triggers the acquisition task at the rising edge of the PPS signal and reads the output data of the ADC module when it detects that the output signal of the DRDY pin of the ADC module is at a falling edge.

[0009] Temperature-compensated crystal oscillator is used to provide a sampling time reference for the ADC module;

[0010] The central control unit calculates the error of the temperature-compensated crystal oscillator based on the DRDY signal from the ADC module and the PPS signal from the GPS module, calculates the correction value based on the error, and adjusts the sampling frequency of the ADC module based on the correction value.

[0011] Furthermore, the error of the temperature-compensated crystal oscillator is calculated based on the DRDY signal from the ADC module and the PPS signal from the GPS module, including:

[0012] Enable interrupt services for the DRDY and PPS signals;

[0013] When the first DRDY signal from the ADC module arrives, take it as the first sampling point N1, clear the TIM timer counter of the central control unit to zero, and start timing counting from zero. When the second DRDY signal arrives, take it as the second sampling point N2, and read the value of the TIM timer counter.

[0014] When the PPS signal interruption signal arrives, the GPS module acquires two PPS signals, which are designated as the first PPS signal and the second PPS signal. The acquisition time of the first PPS signal and the second PPS signal is provided by the GPS module.

[0015] Calculate the time difference between the first PPS signal and the first sampling point to obtain the first offset time T1;

[0016] Calculate the time difference between the second PPS signal and the second sampling point to obtain the second offset time T2;

[0017] The calculation error is: W=(N2-N1)*sampling interval+T2-T1, where the sampling interval is the time interval between the first sampling point N1 and the second sampling point N2, and W is the error.

[0018] Furthermore, the correction value is calculated based on the error as follows: Y = (64 * (2097152 * W - 15625 * X)) / (W - 1000000), where Y is the new correction value and X is the initial correction value.

[0019] Furthermore, the sampling frequency of the ADC module is adjusted according to the correction value, including:

[0020] Enable the sampling rate converter function connected to the ADC module.

[0021] The sampling rate converter adjusts the data stream output by the modulator according to the correction value to make the sampling frequency consistent with the target sampling frequency.

[0022] Furthermore, the sampling rate converter adjusts the data stream output by the modulator according to the correction value, including: the central control unit writes the correction value into the register of the sampling rate converter.

[0023] Another embodiment of this application provides a method for accuracy correction of a seismic data acquisition system, including:

[0024] Acquire the PPS signal from the GPS module, trigger the acquisition task at the rising edge of the PPS signal, and read the output data of the ADC module when the falling edge of the DRDY pin output signal of the ADC module is detected.

[0025] The error of the temperature-compensated crystal oscillator is calculated based on the DRDY signal from the ADC module and the PPS signal from the GPS module. The correction value is then calculated based on the error, and the sampling frequency of the ADC module is adjusted based on the correction value.

[0026] Furthermore, the error of the temperature-compensated crystal oscillator is calculated based on the DRDY signal from the ADC module and the PPS signal from the GPS module, including:

[0027] Enable interrupt services for the DRDY and PPS signals;

[0028] The first DRDY signal from the ADC module is taken as the first sampling point N1, and the timing count starts from zero. The second DRDY signal is taken as the second sampling point N2, and the count value is read.

[0029] When the PPS signal interruption signal arrives, the GPS module acquires two PPS signals, which are designated as the first PPS signal and the second PPS signal. The acquisition time of the first PPS signal and the second PPS signal is provided by the GPS module.

[0030] Calculate the time difference between the first PPS signal and the first sampling point to obtain the first offset time T1;

[0031] Calculate the time difference between the second PPS signal and the second sampling point to obtain the second offset time T2;

[0032] The calculation error is: W=(N2-N1)*sampling interval+T2-T1, where the sampling interval is the time interval between the first sampling point N1 and the second sampling point N2, and W is the error.

[0033] Further, the correction value is calculated based on the error, including: the correction value is calculated as: Y=(64*(2097152*W-15625*X)) / (W-1000000), where Y is the new correction value and X is the initial correction value.

[0034] Furthermore, the sampling frequency of the ADC module is adjusted according to the correction value, including:

[0035] Enable the sampling rate converter function connected to the ADC module.

[0036] The sampling rate converter adjusts the data stream output by the modulator according to the correction value to make the sampling frequency consistent with the target sampling frequency.

[0037] Furthermore, the sampling rate converter adjusts the data stream output by the modulator according to the correction value, including writing the correction value into the register of the sampling rate converter.

[0038] Compared with the prior art, the advantages of this application are as follows: This application can estimate the deviation of the temperature compensation crystal oscillator in real time, realize frequency error measurement and dynamic compensation by adjusting the sampling frequency of the ADC module, enhance the time and frequency stability of the seismic data acquisition system, and can be used for high-precision seismic monitoring. Attached Figure Description

[0039] Figure 1 A block diagram of a seismic data acquisition system provided in this application embodiment;

[0040] Figure 2 A timing diagram for acquiring the DRDY and PPS signals provided in the embodiments of this application. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0042] like Figure 1 As shown, an earthquake data acquisition system includes a central control unit, a GPS module, a temperature-compensated crystal oscillator, and an ADC module. The central control unit connects to other units and serves as the system core; the GPS module provides accurate time synchronization and high-precision positioning performance for use in the node-level earthquake data acquisition system; the temperature-compensated crystal oscillator provides the system with a time reference; the ADC module's DRDY pin (data ready pin) outputs a sampling completion signal, triggered by the system clock; finally, the raw earthquake data blocks are written to an SD card in real time.

[0043] During seismic exploration, several acquisition nodes are deployed in various areas of the field. Each acquisition node is equipped with a seismic data acquisition system, and its power is turned on. After the seismic data acquisition system is powered on, the charging port is checked to see if it is charging. If the node is charging, it enters a charging monitoring state; otherwise, it enters a self-test. The self-test indicators include not only the system's basic information status but also battery voltage, remaining storage space, current sampling frequency, gain, sensitivity, damping, natural frequency, arrangement noise, temperature-compensated crystal oscillator accuracy, and the last time synchronization time. The self-test parameters are sent to the control center to determine whether the node is normal. When a faulty node is found, manual troubleshooting or repair is required. After passing the self-test, each acquisition station begins acquiring seismic data. After passing the self-test, the GPS module receives the GPS satellite synchronization signal and begins acquiring seismic data.

[0044] In this embodiment, the ADC module can be a 32-bit high-resolution ADC module of model ADS1285. The central control unit is connected to the DRDY pin of the ADC module through an interrupt pin. The central control unit reads data on the falling edge of the output signal of the DRDY pin. The central control unit acquires the PPS signal (pulses per second) of the GPS module, triggers the acquisition task at the rising edge of the PPS signal, and reads the output data of the ADC module when it detects that the output signal of the DRDY pin of the ADC module is a falling edge.

[0045] After time synchronization is completed, the crystal in the temperature-compensated crystal oscillator will deviate due to temperature, aging, and other reasons. The central control unit of this application calculates the error of the temperature-compensated crystal oscillator based on the DRDY signal (data ready signal) of the ADC module and the PPS signal of the GPS module, calculates the correction value based on the error, and adjusts the sampling frequency of the ADC module based on the correction value. If the temperature-compensated crystal oscillator has a frequency deviation, the actual sampling frequency of the ADC module will deviate from the set value. The error of the temperature-compensated crystal oscillator is calculated through the DRDY signal of the ADC module and the PPS signal of the GPS module without the need for external instrument measurement.

[0046] In one embodiment, see Figure 2 The timing diagram shown illustrates the acquisition of DRDY and PPS signals. The error of the temperature-compensated crystal oscillator is calculated based on the DRDY signal from the ADC module and the PPS signal from the GPS module, including:

[0047] Enable interrupt services for the DRDY and PPS signals;

[0048] When the first DRDY signal from the ADC module arrives, take it as the first sampling point N1, clear the TIM timer counter of the central control unit to zero, and start timing counting from zero. When the second DRDY signal arrives, take it as the second sampling point N2, and read the value of the TIM timer counter.

[0049] When the PPS signal interruption signal arrives, the GPS module acquires two PPS signals, which are designated as the first PPS signal and the second PPS signal. The acquisition time of the first PPS signal and the second PPS signal is provided by the GPS module.

[0050] Calculate the time difference between the first PPS signal and the first sampling point to obtain the first offset time T1;

[0051] Calculate the time difference between the second PPS signal and the second sampling point to obtain the second offset time T2;

[0052] The calculation error is: W=(N2-N1)*sampling interval+T2-T1, where the sampling interval is the time interval between the first sampling point N1 and the second sampling point N2, and W is the error.

[0053] To measure and compensate for the accuracy of the temperature-compensated crystal oscillator based on the DRDY signal from the ADC module and the PPS signal from the GPS module, the key is to compare the system clock driven by the temperature-compensated crystal oscillator with the time reference of the GPS PPS signal. The temperature-compensated crystal oscillator provides a time reference for the ADC module during data acquisition. The clock provided by the temperature-compensated crystal oscillator directly affects the DRDY signal. Therefore, the error of the temperature-compensated crystal oscillator can be inferred by measuring the DRDY signal, and further frequency correction can be performed through the sampling rate converter (SRC) connected to the ADC module.

[0054] In one embodiment, the error correction value is calculated as: Y=(64*(2097152*W-15625*X)) / (W-1000000), where Y is the new correction value and X is the initial correction value.

[0055] Adjusting the sampling frequency of the ADC module according to the correction value includes:

[0056] Enable the sampling rate converter function connected to the ADC module.

[0057] The sampling rate converter adjusts the data stream output from the modulator based on the correction value to match the sampling frequency with the target sampling frequency. The correction value is written as a compensation factor into the sampling rate converter's register.

[0058] The compensation process corrects the inherent bias of the temperature-compensated crystal oscillator by adjusting the compensation factor to "slow down or speed up" the output frequency of the data stream from the modulator. This occurs when the data reaches the size of the data buffer.

[0059] The sampling rate converter connected to the ADC module is disabled before the sampling frequency of the ADC module is adjusted by the correction value, that is, the data is passed through without compensation. After the error is calculated, it is enabled and written to the register of the sampling rate converter for frequency compensation. Therefore, the sampling rate converter is disabled by default after the initial power-on reset. At this time, the accuracy of the temperature-compensated crystal oscillator before calibration is measured. The error obtained is the error of the temperature-compensated crystal oscillator. According to the formula, the error is: W=(N2-N1)*sampling interval+T2-T1, where the sampling interval is the time interval between the first sampling point N1 and the second sampling point N2, and W is the error.

[0060] The error of the temperature-compensated crystal oscillator is obtained. If the result is too large, it means that the frequency of the temperature-compensated crystal oscillator is too high; otherwise, it means that the frequency of the temperature-compensated crystal oscillator is too low.

[0061] The initial correction value is a value that can be set at any time; it can be zero, indicating no correction. Based on the initial correction value X and the error, a new correction value Y is obtained, which is then written into the sampling rate converter's register in 16-bit two's complement form, thereby changing the sampling frequency of the ADC module.

[0062] A sample rate converter (SRC) compensates for clock frequency errors by resampling the modulator data.

[0063] On the other hand, the accuracy correction method for a seismic data acquisition system provided in this application embodiment can be understood in comparison with the aforementioned seismic data acquisition system, including:

[0064] The system acquires the PPS signal from the GPS module, triggers the acquisition task at the rising edge of the PPS signal, and reads the output data of the ADC module when the falling edge of the DRDY pin output signal is detected. The ADC module's output data is acquired according to the seismic data collected at the sampling frequency. The sampling frequency refers to the number of times the ADC module samples the analog signal per unit time. For example, an ADC module with a sampling frequency of 1000Hz will perform 1000 samples per second.

[0065] The error of the temperature-compensated crystal oscillator is calculated based on the DRDY signal from the ADC module and the PPS signal from the GPS module. The correction value is then calculated based on the error, and the sampling frequency of the ADC module is adjusted based on the correction value.

[0066] The DRDY signal is the data ready signal for the ADC module, indicating that the ADC module has completed a data conversion and the data can be read. The PPS signal is the second pulse signal of the GPS module, generated once per second, used for high-precision time synchronization. The ADC module is started to begin sampling and output the DRDY signal. The GPS module is started to ensure stable output of the PPS signal. The PPS signal is used as a time base, and the rising edge time of each PPS signal is recorded.

[0067] In one embodiment, calculating the error of the temperature-compensated crystal oscillator based on the DRDY signal from the ADC module and the PPS signal from the GPS module includes:

[0068] Enable interrupt services for the DRDY and PPS signals;

[0069] The first DRDY signal from the ADC module is taken as the first sampling point N1, and the timing count starts from zero. The second DRDY signal is taken as the second sampling point N2, and the count value is read.

[0070] When the PPS signal interruption signal arrives, the GPS module acquires two PPS signals, which are designated as the first PPS signal and the second PPS signal. The acquisition time of the first PPS signal and the second PPS signal is provided by the GPS module.

[0071] Calculate the time difference between the first PPS signal and the first sampling point to obtain the first offset time T1;

[0072] Calculate the time difference between the second PPS signal and the second sampling point to obtain the second offset time T2;

[0073] The calculation error is: W=(N2-N1)*sampling interval+T2-T1, where the sampling interval is the time interval between the first sampling point N1 and the second sampling point N2, and W is the error.

[0074] In one embodiment, calculating the correction value based on the error includes: calculating the correction value based on the error as: Y=(64*(2097152*W-15625*X)) / (W-1000000), where Y is the new correction value and X is the initial correction value.

[0075] Adjust the sampling frequency of the ADC module with the obtained correction value. First, enable the sampling rate converter function connected to the ADC module.

[0076] The sampling rate converter adjusts the data stream output from the modulator based on the correction value to match the sampling frequency with the target sampling frequency. The modulator here belongs to the ADC module and is used to convert the input analog signal into a digital signal.

[0077] The sampling rate converter adjusts the data stream output from the modulator based on the correction value, including writing the correction value into the sampling rate converter's register. This completes the correction of the seismic data acquisition system, resulting in more accurate alignment of the seismic signal.

[0078] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A seismic data acquisition system characterized by, The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal.

2. A method of precision correction of a seismic data acquisition system, characterized in that, The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and GPS module PPS signal. 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The application relates to a temperature compensation crystal oscillator error calculation method based on ADC module DRDY signal and The first DRDY signal of the ADC module is taken as a first sampling point N1, and a timing count is started from zero, the second DRDY signal is taken as a second sampling point N2, and a count value is read; When the interrupt signal of the PPS signal arrives, two PPS signals of the GPS module are acquired, which are taken as a first PPS signal and a second PPS signal, and the acquisition time of the first PPS signal and the second PPS signal is provided by the GPS module; A time difference between the first PPS signal and the first sampling point is calculated to obtain a first offset time T1; A time difference between the second PPS signal and the second sampling point is calculated to obtain a second offset time T2; An error is calculated as: W=(N2-N1)*sampling interval+T2-T1, wherein the sampling interval is a time interval between the first sampling point N1 and the second sampling point N2, and W is the error; A correction value is calculated according to the error, including: the correction value is calculated according to the error as: Y=(64*(2097152*W-15625*X)) / (W-1000000), wherein Y is a new correction value, and X is an initial correction value; The sampling frequency of the ADC module is adjusted according to the correction value, including: The sampling rate converter function connected with the ADC module is started, The sampling rate converter adjusts the data stream output by the modulator according to the correction value, so that the sampling frequency is consistent with the target sampling frequency; The sampling rate converter adjusts the data stream output by the modulator according to the correction value, including: the correction value is written into the register of the sampling rate converter.

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