Abstract
In seismic exploration for oil and gas, a grid of 2,000 to 30,000 nodes is formed to acquire reflected wave signals from the rock layers in the Earth. Each node consists of a sensor, complete data acquisition system with self-test, and telemetry for returning data to a central recording unit. This demanding application requires a highly linear, wide dynamic range data acquisition system with a 0.1-200 Hz bandwidth. A large number of nodes operating simultaneously require that each node consume very low power. The components of each data acquisition node are: a geophone or a hydrophone (sensors for land and marine exploration respectively), a programmable gain differential amplifier, a delta-sigma analog to digital converter, a multi-function decimation filter, and a high precision DAC for calibration and self-test. Each of these components is optimally designed for low power in large sensor arrays. The acquisition node requires self-calibration capability and operation in a synchronous mode where all channels acquire data simultaneously. A data acquisition system that meets these requirements has been designed and tested. The overall performance of the system is better than 112 dB linearity (THD) and 123 dB dynamic range (SNR) at 500 SPS. The power consumption for the data acquisition portion of a single node is 105 mW from a 5 V analog power supply.
Published Version
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