Seismic data acquisition system and precision correction method

Abstract

The invention belongs to the field of seismic exploration, and relates to a seismic data acquisition system and a precision correction method, and the system comprises a central control unit which obtains a PPS signal of a GPS module, triggers an acquisition task at a rising edge of the PPS signal, and reads output data of an ADC module when detecting that a DRDY pin output signal of the ADC module is a falling edge; the temperature compensation crystal oscillator is used for providing a sampling time reference for the ADC module; the central control unit calculates the error of the temperature compensation 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. According to the invention, the deviation of the temperature compensation crystal oscillator can be estimated in real time, frequency error measurement and dynamic compensation are realized by adjusting the sampling frequency of the ADC module, the time-frequency stability of the seismic data acquisition system is enhanced, and the method can be used for high-precision seismic monitoring.

Description

Technical Field

[0001] The present application relates to the field of seismic exploration, and specifically to a seismic data acquisition system and an accuracy correction method. Background Art

[0002] Modern seismic monitoring instruments widely utilize high-precision analog-to-digital converters to obtain detailed information about seismic waveforms. This high-resolution, high-rate acquisition mode generates a massive amount of raw data, placing higher demands on time synchronization during data acquisition. Inadequate time synchronization can severely impact the accurate alignment of seismic signals, leading to significant errors in data analysis and rendering the acquisition results ineffective.

[0003] To achieve low power consumption in the seismic data acquisition system, dynamic power management technology is employed after the GPS module successfully synchronizes time. 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 to provide time services. However, temperature-compensated crystal oscillators are sensitive to temperature, and their frequency shifts with temperature changes. Fieldwork is a long-term operation, and the accumulated frequency drift can lead to significant cumulative errors. When the maximum error allowed by the synchronization system is reached (one sampling interval), the processor module manages the power supply to the functional modules and activates the GPS module to accurately correct the accumulated error of the temperature-compensated crystal oscillator. While this reduces power consumption to a certain extent, the characteristics of the temperature-compensated crystal oscillator require the GPS module to be continuously activated for correction, thus failing to achieve maximum power reduction.

[0004] As acquisition time increases, the frequency drift of the crystal oscillator at the acquisition station leads to significant accumulation of time errors, necessitating that the time synchronization system be capable of error compensation or correction. Currently, temperature-compensated crystal oscillators are widely used in seismic data acquisition systems as local frequency references. The accuracy of existing temperature-compensated crystal oscillators typically relies on external frequency measurement instruments and requires the GPS module to be constantly powered on for frequency compensation. These high-cost, complex structures make them unsuitable for embedded or resource-constrained scenarios. Although the GPS module's PPS signal (one pulse per second) provides a second-level time reference, seismic data acquisition systems still struggle to directly and accurately measure the deviation of the temperature-compensated crystal oscillator. Summary of the Invention

[0005] The embodiments of the present application provide a seismic data acquisition system to solve the problem of insufficient time synchronization performance of data acquisition, which affects the accurate alignment of seismic signals.

[0006] An embodiment of the present application also provides a method for calibrating the accuracy of a seismic data acquisition system.

[0007] According to the first aspect of the application, a seismic data acquisition system comprises: A central control unit acquires the PPS signal of the GPS module, and connects the DRDY pin of the ADC module through the interrupt pin, 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 output signal of the DRDY pin of the ADC module is a falling edge. A 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.

[0008] Further, calculating 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 comprises: Starting the interrupt service of the DRDY signal and the PPS signal; Taking the arrival of the first DRDY signal of the ADC module as the first sampling point N1, clearing the TIM timing counter of the central control unit, starting timing counting from zero, taking the arrival of the second DRDY signal as the second sampling point N2, and reading the value of the TIM timing counter; When the interrupt signal of the PPS signal arrives, acquiring two PPS signals of the GPS module, which are the first PPS signal and the second PPS signal, and the acquisition time of the first PPS signal and the second PPS signal is provided by the GPS module; Calculating the time difference between the first PPS signal and the first sampling point to obtain the first offset time T1; Calculating the time difference between the second PPS signal and the second sampling point to obtain the second offset time T2; The error is calculated as: 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.

[0009] Further, the correction value is calculated according to 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.

[0010] Further, adjusting the sampling frequency of the ADC module according to the correction value comprises: Starting the sampling rate converter function connected to the ADC module, 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.

[0011] Further, the sampling rate converter adjusts the data stream outputted by the modulator according to the correction value, comprising: the central control unit writes the correction value into the register of the sampling rate converter.

[0012] The precision correction method of the seismic data acquisition system according to another aspect of the embodiment of the present application comprises: The PPS signal of the GPS module is acquired, the acquisition task is triggered at the rising edge of the PPS signal, and the output data of the ADC module is read when it is detected that the DRDY pin output signal of the ADC module is a falling edge. The error of the temperature-compensated crystal oscillator is calculated according to the DRDY signal of the ADC module and the PPS signal of the GPS module, the correction value is calculated according to the error, and the sampling frequency of the ADC module is adjusted according to the correction value.

[0013] Further, the error of the temperature-compensated crystal oscillator is calculated according to the DRDY signal of the ADC module and the PPS signal of the GPS module, comprising: The interrupt service of the DRDY signal and the PPS signal is started; The first DRDY signal of the ADC module is taken as the first sampling point N1, the timing count is started from zero, the second DRDY signal is taken as the second sampling point N2, and the count value is read; When the interrupt signal of the PPS signal arrives, the two PPS signals of the GPS module are acquired, which are taken as the first PPS signal and the second PPS signal, and the acquisition time of the first PPS signal and the second PPS signal is provided by the GPS module; The time difference between the first PPS signal and the first sampling point is calculated to obtain the first offset time T1; The time difference between the second PPS signal and the second sampling point is calculated to obtain the second offset time T2; The error is calculated as: W=(N2-N1)*sampling interval+T2-T1, wherein the sampling interval is the time interval between the first sampling point N1 and the second sampling point N2, and W is the error.

[0014] Further, the correction value is calculated according to the error, comprising: the correction value is calculated according to the error as: Y=(64*(2097152*W-15625*X)) / (W-1000000), wherein Y is the new correction value, and X is the initial correction value.

[0015] Further, the sampling frequency of the ADC module is adjusted according to the correction value, comprising: The function of the sampling rate converter connected to the ADC module is started, The sampling rate converter adjusts the data stream outputted by the modulator according to the correction value, so that the sampling frequency is consistent with the target sampling frequency.

[0016] Further, the sampling rate converter adjusts the data stream output by the modulator according to the correction value, including: writing the correction value into a register of the sampling rate converter.

[0017] Compared with the prior art, the application has the beneficial effects that the application can estimate the deviation of the temperature-compensated crystal oscillator in real time, realizes frequency error measurement and dynamic compensation by adjusting the sampling frequency of the ADC module, enhances the time-frequency stability of the seismic data acquisition system, and can be used for high-precision seismic monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A block diagram of a seismic data acquisition system is provided for the embodiments of the application; Figure 2 A timing diagram for collecting the DRDY signal and the PPS signal is provided for the embodiments of the application. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the application more clear and understandable, the application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0020] As shown in Figure 1 A seismic data acquisition system includes a central control unit, a GPS module, a temperature-compensated crystal oscillator and an ADC module. The central control unit is connected with other units and serves as the core of the system; the GPS module provides accurate timing and high-precision positioning performance for application in the seismic data acquisition system of the node; the temperature-compensated crystal oscillator provides time reference service for the system; the DRDY pin (data ready pin) of the ADC module outputs a sampling completion signal, which is triggered based on the system clock; and finally, the seismic raw data block is written to the SD card in real time.

[0021] During seismic exploration, a number of acquisition nodes are arranged in each region in the field, and each acquisition node is arranged with a seismic data acquisition system and the power supply is turned on. After the seismic data acquisition system is powered on, it is measured whether the charging port is charging. If the node is charging, it enters the monitoring charging state, otherwise it enters the node self-checking. The self-checking indicators include not only the system's own basic information state but also the battery voltage, the remaining storage space, the current sampling frequency, the gain, the sensitivity, the damping, the natural frequency, the arrangement noise, the temperature-compensated crystal oscillator accuracy, the last time synchronization time, etc., and the self-checking parameters are sent to the control center to determine whether the node is normal. When a faulty node appears, manual troubleshooting or repair is needed. After the self-checking is qualified, each acquisition station starts to collect seismic data, and after the self-checking is qualified, the GPS module receives the GPS satellite synchronization signal and starts to collect seismic data.

[0022] In the embodiment of the application, the ADC module can adopt a 32-bit high-resolution ADC module of model ADS1285, the central control unit is connected with the DRDY pin of the ADC module through an interrupt pin, the central control unit reads data at the falling edge of the output signal of the DRDY pin, the central control unit acquires the PPS signal (pulse per second) of the GPS module, triggers a collection task at the rising edge of the PPS signal, and reads the output data of the ADC module when detecting that the output signal of the DRDY pin of the ADC module is a falling edge.

[0023] When the time synchronization is completed, the crystal in the temperature-compensated crystal oscillator will be offset due to temperature, aging and other reasons, the central control unit of the application calculates the error of the temperature-compensated crystal oscillator according to the DRDY signal (data ready 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. If the temperature-compensated crystal oscillator has a frequency offset, 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 instruments to measure.

[0024] In an embodiment, referring to the timing diagram of the DRDY signal and the PPS signal shown in Figure 2 The error of the temperature-compensated crystal oscillator is calculated according to the DRDY signal of the ADC module and the PPS signal of the GPS module, including: Starting the interrupt service of the DRDY signal and the PPS signal; Taking the arrival of the first DRDY signal of the ADC module as the first sampling point N1, clearing the TIM timing counter of the central control unit, starting timing counting from zero, taking the arrival of the second DRDY signal as the second sampling point N2, and reading the value of the TIM timing counter; When the interrupt signal of the PPS signal arrives, acquiring two PPS signals of the GPS module, 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; Calculating the time difference between the first PPS signal and the first sampling point to obtain a first offset time T1; Calculating the time difference between the second PPS signal and the second sampling point to obtain a second offset time T2; The error is calculated as: W=(N2-N1)*sampling interval+T2-T1, wherein the sampling interval is the time interval between the first sampling point N1 and the second sampling point N2, and W is the error.

[0025] The key to measuring the precision of the temperature-compensated crystal oscillator and compensating it according to the DRDY signal of the ADC module and the PPS signal of the GPS module is to compare the time reference of the system clock driven by the temperature-compensated crystal oscillator with the PPS signal of the GPS. The temperature-compensated crystal oscillator provides the time reference for the ADC module during the data acquisition process. The clock provided by the temperature-compensated crystal oscillator can directly affect 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 by the sample rate converter (SRC) connected to the ADC module.

[0026] In an embodiment, the error 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.

[0027] The sampling frequency of the ADC module is adjusted according to the correction value, including: enabling the sample rate converter function connected to the ADC module, The sample 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. The correction value is written into the register of the sample rate converter as a compensation factor.

[0028] The compensation process is to "slow down or speed up" the output frequency of the data stream output by the modulator by adjusting the compensation factor, thereby correcting the inherent deviation of the temperature-compensated crystal oscillator. When the data reaches the size of the data buffer.

[0029] The sample rate converter connected to the ADC module is in a disabled state before adjusting the sampling frequency of the ADC module according to the correction value, i.e. the data is directly transmitted without compensation. After the error is calculated, the register of the sample rate converter is enabled for frequency compensation. Therefore, the sample rate converter is disabled by default after the initial power-on reset. At this time, the precision of the temperature-compensated crystal oscillator before calibration is measured, and 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.

[0030] 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 large; otherwise, it means that the frequency of the temperature-compensated crystal oscillator is too small.

[0031] The initial correction value is a value that can be set at any time and can be zero, which means no correction when it is zero. According to the initial correction value X and the error, the new correction value Y is obtained, which is written into the register of the sample rate converter in the form of 16-bit complement, thereby changing the sampling frequency of the ADC module.

[0032] A sample rate converter (SRC) compensates for clock frequency errors by resampling the modulator data.

[0033] In another aspect, the precision correction method of the seismic data acquisition system provided by the embodiments of the present application can be understood in conjunction with the above-mentioned seismic data acquisition system, and comprises the following steps: The PPS signal of the GPS module is acquired, the acquisition task is triggered at the rising edge of the PPS signal, and the output data of the ADC module is read when it is detected that the DRDY pin output signal of the ADC module is a falling edge; the output data of the ADC module is seismic data collected according to a sampling frequency. The sampling frequency refers to the number of times of sampling of an analog signal by the ADC module per unit time. For example, an ADC module with a sampling frequency of 1000 Hz will sample 1000 times per second.

[0034] The error of the temperature-compensated crystal oscillator is calculated according to the DRDY signal of the ADC module and the PPS signal of the GPS module, a correction value is calculated according to the error, and the sampling frequency of the ADC module is adjusted according to the correction value.

[0035] The DRDY signal is the data ready signal of 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, which is generated once per second and is used for high-precision time synchronization. The ADC module is started to start sampling and output the DRDY signal. The GPS module is started to ensure that the PPS signal can be stably output. The PPS signal is used as a time reference to record the time of the rising edge of each PPS signal.

[0036] In an embodiment, the error of the temperature-compensated crystal oscillator is calculated according to the DRDY signal of the ADC module and the PPS signal of the GPS module, comprising: The interrupt service of the DRDY signal and the PPS signal is started; The first DRDY signal of the ADC module is taken as the first sampling point N1, and the second DRDY signal is taken as the second sampling point N2, and the count value is read; When the interrupt signal of the PPS signal arrives, the two PPS signals of the GPS module are acquired, which are taken as the first PPS signal and the second PPS signal, and the acquisition time of the first PPS signal and the second PPS signal is provided by the GPS module; The time difference between the first PPS signal and the first sampling point is calculated to obtain the first offset time T1; The time difference between the second PPS signal and the second sampling point is calculated to obtain the second offset time T2; The calculated 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.

[0037] In one embodiment, calculating the correction value according to the error includes: calculating the correction value according to 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.

[0038] The obtained correction value is used to adjust the sampling frequency of the ADC module. First, turn on the sampling rate converter function connected to the ADC module. The sampling rate converter adjusts the data stream output by the modulator based on the correction value to align 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.

[0039] The sample rate converter adjusts the modulator output data stream based on the correction value, including writing the correction value into a register of the sample rate converter. This completes the calibration of the seismic data acquisition system, resulting in more accurate alignment of the seismic signals.

[0040] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A seismic data acquisition system, characterized in that: include: The central control unit obtains the PPS signal of the GPS module and connects it to the DRDY pin of the ADC module through the 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 the output signal of the DRDY pin of the ADC module is detected to be a falling edge. Temperature compensated crystal oscillator, used to provide sampling time reference for 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.

2. The seismic data acquisition system according to claim 1, characterized in that: Calculate the error of the temperature-compensated crystal oscillator based on the DRDY signal of the ADC module and the PPS signal of the GPS module, including: Enable the interrupt service of DRDY signal and PPS signal; The first DRDY signal from the ADC module is used as the first sampling point N1, the TIM timing counter of the central control unit is cleared, and the timing counting starts from zero. The second DRDY signal is used as the second sampling point N2, and the value of the TIM timing counter is read; When the interrupt signal of the PPS signal arrives, two PPS signals of the GPS module are obtained, which are counted as the first PPS signal and the second PPS signal, and the acquisition time of the first PPS signal and the second PPS signal is provided by the GPS module; Calculate the time difference between the first PPS signal and the first sampling point to obtain a first offset time T1; Calculate the time difference between the second PPS signal and the second sampling point to obtain a second offset time T2; The calculated 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.

3. The seismic data acquisition system according to claim 1, characterized in that: The correction value calculated based on the error is: Y=(64*(2097152*W-5625*X)) / (W-1000000), where Y is the new correction value and X is the initial correction value.

4. The seismic data acquisition system according to claim 3, characterized in that: Adjust the sampling frequency of the ADC module according to the correction value, including: Enable the sampling rate converter function connected to the ADC module. 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.

5. The seismic data acquisition system according to claim 4, characterized in that: The sampling rate converter adjusts the data stream output by the modulator according to the correction value, comprising: a central control unit writing the correction value into a register of the sampling rate converter.

6. A method for calibrating the accuracy of a seismic data acquisition system, characterized in that: include: Get the PPS signal of 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 output signal of the DRDY pin of the ADC module is detected to be a falling edge; An error of the temperature-compensated crystal oscillator is calculated according to the DRDY signal of the ADC module and the PPS signal of the GPS module, a correction value is calculated according to the error, and a sampling frequency of the ADC module is adjusted according to the correction value.

7. The accuracy correction method of the seismic data acquisition system according to claim 6, characterized in that: Calculate the error of the temperature-compensated crystal oscillator based on the DRDY signal of the ADC module and the PPS signal of the GPS module, including: Enable the interrupt service of DRDY signal and PPS signal; The first DRDY signal from the ADC module is used as the first sampling point N1, and the timing count is started from zero. The second DRDY signal is used as the second sampling point N2, and the count value is read. When the interrupt signal of the PPS signal arrives, two PPS signals of the GPS module are obtained, which are counted as the first PPS signal and the second PPS signal, and the acquisition time of the first PPS signal and the second PPS signal is provided by the GPS module; Calculate the time difference between the first PPS signal and the first sampling point to obtain a first offset time T1; Calculate the time difference between the second PPS signal and the second sampling point to obtain a second offset time T2; The calculated 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.

8. The accuracy correction method of the seismic data acquisition system according to claim 6, characterized in that: Calculating a correction value according to the error includes: calculating the correction value according to the error is: Y=(64*(2097152*W-15625*X)) / (W-1000000), where Y is a new correction value and X is an initial correction value.

9. The accuracy correction method of the seismic data acquisition system according to claim 6, characterized in that: Adjust the sampling frequency of the ADC module according to the correction value, including: Enable the sampling rate converter function connected to the ADC module. 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.

10. The accuracy correction method of the seismic data acquisition system according to claim 9, characterized in that: The sampling rate converter adjusts the data stream output by the modulator according to the correction value, including: writing the correction value into a register of the sampling rate converter.

Images