Prototype Development Of Broadband Earthquake Recorder With WiFi Wireless Monitoring Function

With three decades of reform and opening up, China’s comprehensivenational strength and people’s living standard has been remarkable to raisethe overall level. However, at the same time, it is also facing increasinglyprominent geoscience problems such as resources、energy、the environmentand the large-scale geological disasters,etc. The most effective way to solvethe problem is to start from the understanding of the deep crust of EarthScience Information. From the point of view of long-term national economicdevelopment strategy, the development of deep detection technology andrelated instruments and equipments provide the necessary scientific andtechnological support for deep mineral exploration and development of oil andgas resources, disaster prevention and mitigation, as well as to find out thelaws of nature activities. In many geophysical methods, the method of thenatural seismic exploration of deep earth structure has many advantages suchas deeper probing depth, easy to operate, low cost etc. And it quicklydeveloped into an important means of research and exploration of the deepEarth. On the other hand, destructive earthquake occurred sometimes and thescientific community is still unable to accurately predict earthquakes. Butnatural earthquake early warning is an important measure to reduce theearthquake disaster. The natural earthquake early warning system is a largecomplex system, its core part is the broad-band high-precision seismic dataacquisition system. To provide technical support for better implementation ofthe crust exploration project, and reverse the long-term dependence onimports of deep detection instrument and break the monopoly of foreigntechnology, this paper fully learns and studies the natural seismic exploration instrument of domestic and abroad, proposes the overall program ofbroadband seismic recorder prototype with WiFi wireless monitoring function,completes the development of the prototype and does indoor testing andpreliminary test to verify the validity and reliability of the prototype.Starting from natural seismic exploration method and background noiseimaging method, research the difference between natural earthquakeobservation and petroleum mineral exploration, and the need of seismicinstruments for natural seismic observations; learn the principles and themethod of the use of broadband seismometer; collect indexes of domestic andabroad broadband seismic instruments and research developments; andpropose general scheme of wideband seismic recorder prototype developmentwhich can meet actual demand.According to the function of the instrument system, it is divided into fiveboards: interface board, auxiliary board, acquisition board, control board andGPS positioning board. The first four boards do the physical and electricalconnection through the European connector, constituting the broadbandseismic data acquisition system. GPS positioning board conducts serialcommunication with acquisition system via a standard RS-232bus. The frontside of the interface board is equipped with aviation plugs to connect with theexternal, back face circuit can achieve electrostatic and lightning protection、RS-232level conversion、status indication, etc. According to its function,auxiliary board is divided into the WiFi RF unit and power supply unit,achieving wireless communication, power supply voltage converter, batterycharge management, and supply voltage monitoring function. Acquisitionboard takes24bits A/D chip set as the core, achieving3-channelhigh-precision data acquisition. Control board is responsible for the systemoperation management and data computing.This paper describes and studies low noise acquisition technology, massdata storage technology, a variety of data retrieve technology, intelligent power management technology and weak signal acquisition on anti-jammingtechnology in detail, which are necessary in instrument design. It alsointroduces the principle of the chopper modulation technique which caneffectively eliminate1/f noise, and the application of24bits A/D chip setsolutions. Using dual CF cards structure to achieve the storage of largecapacity earthquake data. In the case which does not affect the observationoperation, achieving the CF card’s plug and replacement. Via combining wiredEthernet, wireless WiFi, with memory card recovery to achieve a flexible datarecovery. For high-power GPS RF unit, WiFi wireless communication unit andacquisition channels, the system designs intelligent power shutdown circuit,turning off the parts which don’t work, to try to reduce the power consumptionof the instrument system level. By modular layout, adding the second stageregulator power to the acquisition board, and separate power supply for analogand digital part. RF circuit and a weak signal acquisition circuit plus a groundedmetal shield. By the measures of using balanced differential circuit to suppresscommon mode interference and using passive LC filter circuit to suppressdifferential mode interference, to strengthen the anti-interference ability of theweak signal acquisition circuit.Conducting the indoor acquisition performance test, the indexes test andthe actual vibration response test in prototype, and compared with foreigninstrument. The results verified the correctness of self-made wideband seismicrecorder prototype design. Its performance indexes is very close with theforeign instrument. Compared with the domestic similar instruments, it has agreat advantage and much higher performance price ratio.