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| | Abstract | | A high-speed resistivity measurement tool using a code division multiple transmission technique was developed and has been utilized in such practical uses as 3D time-lapse monitoring of water infiltration into the vadose zone of levees. The tool can flow electric current at 24 electrodes simultaneously and receive potential at 24 electrodes. Accordingly, we can obtain a total of 576 dataset within only 30 seconds. Because orthogonal matrix is used as the simultaneous current transmission method, we can easily divide individual responses from potential waveforms. When utilizing the tool, we experienced two problems. The one was the crossover of decay curves, and the other was a bias between two decay curves. Originally the tool should have been manufactured to transmit the orthogonal code current appropriately at multiple electrodes. However, insufficient current might distort the orthogonality of signals. So, careful quality check is needful especially to decay curves. |
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