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НаименованиеDigital geophysical station

 

The Land Explorer Digital Geophysical Station was designed to measure geophysical fields over long periods of weeks or months for the purpose of studying the Earth's subsurface structure or to monitor tectonic processes in order to predict natural disasters. The station allows for simultaneous seismological and magnetotelluric monitoring.

The station includes two channels for working with analog signals, one for high frequencies (0.1 to 30 Hz) and one for low frequencies (10-5 to 10-1 Hz). The channel signals are digitized at a frequency of 128 Hz (high) and 4 Hz (low), with bit rates of 16 and 24 bits, respectively. The station has eight high-frequency and five low-frequency channels.

The stations can function autonomously, without an operator, or in stationary mode, with daily service to replace the hard disk where data are recorded. A satellite receiver can be used to synchronize several stations on absolute world time to coordinate measurements in different parts of the planet.

A station consists of peripheral data collection controllers installed near each sensor and powered by a separate battery; a hub station that collects the data and manages the controllers; and a GPS receiver. A notebook PC can be connected to the hub to initialize the controllers and launch the station.

Each controller includes three analog channels (or four on the telluric channel), four Sigma-Delta central processing units (Analog Devices AD 7716), a digital signal processor (ADSP2115), a microcontroller (Dallas Semiconductor DS80C320), an interface converter and a multi-channel power source.

Data coming from the digital signal processors are grouped into packets and sent to the hub. The hub sends a synchronization signal to the controllers every two seconds.

Operating autonomously, the station processes data in real time and determines, based on certain criteria, whether to record so-called events. This requires a sufficiently powerful processor, which also must be able to work with a GPS receiver, allow for hard disk exchange (such as through PCMCIA) and work with an MS-DOS file structure. The MicroPC 4000 controller from Octagon Systems, based on the 386SX-25 processor and PCMCIA-compatible, meets these requirements. However, the MicroPC's power requirements are fairly high, and its write-to-disk speed is several times higher than the speed at which data comes in from the controllers. For that reason, a special hub station controller was developed to manage the controller network, provide a data buffer and manage the MicroPC's power. When this hub station controller accumulates sufficient data, it turns on the MicroPC and transfers the data for processing or writing to hard disk. The programming was done in Borland C++ 3.1.

 

Typical station setup.
 

By Pierre Andrie, Aleksandr Valyushchev, Roman Gezikov,
Vyacheslav Kozlov, Andrey Titov and Eduard Fainberg

Pier Andriye,  Aleksandr Valyushchev,  Roman Gezikov,  Vyacheslav Kozlov,  Andrey Titov,  Eduard Fainberg