Magnetotelluric method is widely used in oil and gas exploration. The corresponding instrument system need to record low noise data at sample rate 2400Hz, 150Hz and 15Hz or other triple frequencies simultaneously. Notch filter is also need to remove 50/60Hz power line interference. Commercial decimation filer chip can only output data at fixed rate at given time. To satisfy the requirement of data acquisition in magnetotelluric exploration, 24-bit DSP56309 chip is used in measurement system. It do two-channel multi-stage decimation filtering and multi-fold 50/60Hz notch filtering for 1-bit output data of ΔΣ modulator, and output data from ESSI and SCI to ARM at sample rate 2400Hz, 150Hz and 15Hz simultaneously.
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