Research On Wireless Clock Synchronization In Geophysical Prospecting Equipment

Geophysical prospecting is a kind of exploration method that takes advantage of the structural properties of different rock formations.Our laboratory has designed a multi-level system for equipment control and data collection in geophysical prospect-ing.In recent years,geophysical exploration has gradually developed towards wireless.Therefore,this article adds wireless communication-related modules on the basis of the existing wired geophysical exploration system,and designs a corresponding wireless clock synchronization scheme.Lay the foundation for the subsequent wirelessization of the systemThe current mainstream wireless geophysical prospecting systems generally use GPS to achieve clock synchronization,but the GPS module has high power consump-tion.For long-term field operations,the Data Acquisition Unit must carry a large num-ber of batteries,which increases the cost of the system.This paper proposes a wireless clock synchronization scheme that does not require a GPS module.In the scheme,clock synchronization includes two parts:frequency synchronization and time synchroniza-tion.Time synchronization realizes the start of the collection work of each Data Acqui-sition Unit at the same time,and frequency synchronization realizes the clock frequency of each Data Acquisition Unit is the same.For wireless time synchronization,this paper proposes a wireless delay test method,which measures the average and distribution of the wireless signal propagation delay between the location to be tested and the Battery Management Unit through mul-tiple wireless communications,and also verifies The reliability of the wireless channel.When deploying Data Acquisition Units for field operations in geophysical prospecting,the average wireless signal propagation delay from the Battery Management Unit to the Data Acquisition Unit can be tested for each Data Acquisition Unit and written into the Data Acquisition Unit,and the Data Acquisition Unit can be based on their respective time delay data Correct the time synchronization signal from the Battery Management Unit to complete the time synchronization.For wireless frequency synchronization,this paper proposes a design method for high frequency stable temperature compensated crystal oscillator.The temperature-compensated crystal oscillator achieves high frequency stability through high-density compensation points and compensates its thermal hysteresis through software algo-rithms.As a result,the final integrated frequency stability reached±250ppb.In order to realize the rapid measurement of a large number of compensation values of a high-stability temperature-compensated crystal oscillator,this paper designs an automatic measurement system that can automatically adjust its frequency and record the compen-sation value.If the crystal oscillator works for a long time,the frequency drift will occur due to aging.To solve this problem,this paper designs a temperature-compensated crys-tal oscillator wireless frequency correction scheme.In this scheme,the Battery Man-agement Unit broadcasts wireless signals at equal intervals,and the acquisition station completes the frequency self-test according to the signal.And the frequency is roughly corrected.Finally,an outdoor comprehensive test of the overall clock synchronization effect lasting 130 hours was carried out.The test simulated the real acquisition process,and the measured clock synchronization error was not more than ±2us,which met the re-quirements of the Data Acquisition Unit in the geophysical exploration equipment for clock synchronization.