| Abstrak/Abstract |
The geoelectric method is one of the geophysical methods in physics that works based on the resistivity properties of the medium. The geoelectric method measures the resistivity value of a medium. In the geoelectric method, there are many types of method such as the Self Potential (SP) method, Mise-ala-Mase, Induction Polarization (IP), Sounding and Mapping. These differences are characterized based on the arrangement of the electrodes and the data acquisition technique. While what is measured is basically the same, namely the potential difference, and the current strength to calculate the resistivity value. The Sounding and Mapping method has several different configurations, such as the Sclumberger, Wenner, Half-Sclumberger, Half-Wenner, Equatorial Dipole, Dipole-dipole, and Pole-dipole configurations. The difference is also characterized based on the electrode arrangement and data acquisition technique. The exact position or distance of each electrode is very important to the reference point. How large is the percentage of error in the position of the electrode placement, it will give the percentage of error. We know that the accuracy of measurements in the field is not only determined by the accuracy of the measuring instrument, it is also determined by the exact placement of the electrode positions, both current and potential electrodes. In this study, a theoretical analysis of the tolerance value/error of electrode placement in geoelectrical measurements is carried out in the field. The method used is error propagation
analysis with the arrangement of Schlumberger, Wenner and Equatorial dipole electrodes. It was found that for the arrangement of the Schlumberger and Wenner configurations, the greater the ratio of the current electrode distance (a) to the potential electrode distance (b), the smaller the relative error of the potential difference reading. The current electrode position error is greater than the potential electrode position error, therefore the current electrode position is positioned precisely. If all 4 electrodes have the same position error, then the relative error will be around the electrode position error and does not depend on the eccentricity value (c= a/b). For the equatorial dipole configuration, the error caused by the angular position error will be greater than the error caused by the position/distance error. The results of the error in the electrode position can be used as a reference for geoelectrical measurements in the field, in order to minimize errors that often appear so far. |
