Abstract

Geophysical exploration using electrical resistivity typically employs the use of four electrodes. During a field survey, these electrodes are progressively relocated to positions that differ from a few meters to hundreds of meters. Consequently, field operations can be exhaustive and time consuming and often lead to mistakes in connecting to correct locations of electrodes and hence poor data quality. This project developed an automated field resistivity system that eliminates these problems while providing the user greater flexibility.

The automation of DC field resistivity is not a new concept. Various systems have been developed and are available today. The system developed in this project differs in its versatility and generic capability. The automation of field resistivity is accomplished by using multiple numbers of field electrodes, digitally selecting these electrodes in a switch box, remotely controlling the resistivity instrument, and recording the results. Controlling the process is the Acquisition Control software, written in Microsoft Visual Basic version 5.0 for Windows 95. The switch box has the capability to input banks of 64 signals, four of which are digitally selected via multiplexers. Once the data are rapidly taken via a laptop computer, they can be analyzed in the field, therefore yielding essentially real-time results, which immediately can guide further investigations. Furthermore, by utilizing the multitasking capabilities of Windows 95, field data can be processed as new data are simultaneously being acquired.

The above system was developed and tested in a controlled laboratory experiment and a field survey. The results from both tests show a working prototype that efficiently and accurately gathered data with time improvements of 500 to 600%. Overall, the development and testing of this prototype was a complete success and a patent is pending.