The Geophysical Instrument for Low Power Data Acquisition (GILDA).

Abstract

The geophysical data acquisition system named GILDA (Geophysical Instrument for Low power Data Acquisition) has been developed by the Osservatorio Vesuviano, department of the Istituto Nazionale di Geofisica e Vulcanologia in Naples (INGV). The main goal of this project was to study, develop and produce a data acquisition system specifically devoted to multiparametric volcano monitoring. INGV policy is to share this instrument and the relative know-how in frameworks of collaborative activities with other institutions involved in geophysical monitoring and research. The first step of the GILDA project has been the realization of an high-resolution seismic datalogger, with 4 channels, different possible sampling rates from 40sps to 1000sps, about 132dB of dynamic range and a very low power consumption of about 840mW at full performances. The GILDA datalogger is a multiboard system composed of a 24 bit sigma-delta ADC board, a central processing unit board based on an ARMv7 core, a timing board for GPS synchronization and a GPS board realized with a Trimble Lassen iQ unit. A module for remote GPS installation is also available allowing placement of the instrument in vaults and areas not covered by GPS signal. The last upgrade of the system is an external board for local data storage based on an SD/SDHC memory card allowing up 32 GB of data (in a typical usage this allows about 1.5 years of storage). At present other instruments are under study for the GILDA project, in particular a multichannel acquisition system specially designed for array applications and another one designed for geochemical data acquisition. The overall production costs of the datalogger system is of about 2500€, making it a very competitive solution for purposes of low budget experiments or seismic networks. It is a very good trade-off among performances, power requirement and costs. The multiboard approach of the datalogger further reduces running costs of the system because in case of faults it is always possible to repair or change only the broken board instead of repair or change the whole object. Data acquisition of the system uses the Earthworm suite running a specialized home developed module. Both are open source software that may be used without any additional fee and they may be run on a GNU/Linux operating system. These conditions allows for further cost reductions compared to some commercial solutions using proprietary and license charged softwares.