A procedure for stable electrical measurements on a rock sample against high contact resistance as a prerequisite for electrical tomography
Abstract As a basis for the electrical tomography of laboratory-scale rock samples (~ 10 cm), we developed a procedure for stable, multi-point, electrical measurement on rock samples that is effective even at high contact and sample resistance. Electrodes were strongly attached to the surface of hig...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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SpringerOpen
2021-06-01
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| Series: | Earth, Planets and Space |
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| Online Access: | https://doi.org/10.1186/s40623-021-01446-9 |
| _version_ | 1818930177373110272 |
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| author | Takeshi Suzuki Ryokei Yoshimura Ken’ichi Yamazaki Naoto Oshiman |
| author_facet | Takeshi Suzuki Ryokei Yoshimura Ken’ichi Yamazaki Naoto Oshiman |
| author_sort | Takeshi Suzuki |
| collection | DOAJ |
| description | Abstract As a basis for the electrical tomography of laboratory-scale rock samples (~ 10 cm), we developed a procedure for stable, multi-point, electrical measurement on rock samples that is effective even at high contact and sample resistance. Electrodes were strongly attached to the surface of high-resistivity rock using conductive and adhesive epoxy. Sustained current injection for long periods into high-resistance rocks was fulfilled using a constant direct current source with high internal resistance. Accurate voltage measurement across the high-resistance rock was accomplished by differential measurement using two high input resistance voltmeters. Measurements of high resistance also require a stable measurement environment: the temperature and humidity in the laboratory were controlled using an air conditioner, a humidifier, a dehumidifier, and a vinyl tent. Signal noise arising from human activities was eliminated by the remote operation of the measuring equipment and switching terminal. The proposed measurement procedure was evaluated in terms of the stability and accuracy of measured values and its applicability to electrical tomography. To assess measurement stability, we performed multiple measurements of a dry granite sample at various levels of absolute humidity. Our procedure recorded highly reproducible measurements under each humidity condition. The observed changes in measured values with absolute humidity indicate the importance of stabilising the temperature and humidity conditions in the laboratory. Applying our technique to multiple plastic samples with known resistivity confirmed its accuracy. To evaluate its applicability to electrical tomography, we measured the potential distribution on a dry granite surface in response to an injected current using a simple 40-electrode array. The potential distribution measured by our procedure agreed well with that predicted by forward modelling, demonstrating the robustness of our procedure in array measurements, and thus indicating its potential applicability to tomographic measurements for a variety of targets even under severe conditions including the relative dryness of ambient humidity. |
| first_indexed | 2024-12-20T03:56:33Z |
| format | Article |
| id | doaj.art-d5d4fb11dadc43e199cbeae5ba5fbbf6 |
| institution | Directory Open Access Journal |
| issn | 1880-5981 |
| language | English |
| last_indexed | 2024-12-20T03:56:33Z |
| publishDate | 2021-06-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Earth, Planets and Space |
| spelling | doaj.art-d5d4fb11dadc43e199cbeae5ba5fbbf62022-12-21T19:54:18ZengSpringerOpenEarth, Planets and Space1880-59812021-06-0173111810.1186/s40623-021-01446-9A procedure for stable electrical measurements on a rock sample against high contact resistance as a prerequisite for electrical tomographyTakeshi Suzuki0Ryokei Yoshimura1Ken’ichi Yamazaki2Naoto Oshiman3Graduate School of Science, Kyoto UniversityDisaster Prevention Research Institute, Kyoto UniversityMiyazaki Observatory, Research Center for Earthquake Prediction, Disaster Prevention Research Institute, Kyoto UniversityDisaster Prevention Research Institute, Kyoto UniversityAbstract As a basis for the electrical tomography of laboratory-scale rock samples (~ 10 cm), we developed a procedure for stable, multi-point, electrical measurement on rock samples that is effective even at high contact and sample resistance. Electrodes were strongly attached to the surface of high-resistivity rock using conductive and adhesive epoxy. Sustained current injection for long periods into high-resistance rocks was fulfilled using a constant direct current source with high internal resistance. Accurate voltage measurement across the high-resistance rock was accomplished by differential measurement using two high input resistance voltmeters. Measurements of high resistance also require a stable measurement environment: the temperature and humidity in the laboratory were controlled using an air conditioner, a humidifier, a dehumidifier, and a vinyl tent. Signal noise arising from human activities was eliminated by the remote operation of the measuring equipment and switching terminal. The proposed measurement procedure was evaluated in terms of the stability and accuracy of measured values and its applicability to electrical tomography. To assess measurement stability, we performed multiple measurements of a dry granite sample at various levels of absolute humidity. Our procedure recorded highly reproducible measurements under each humidity condition. The observed changes in measured values with absolute humidity indicate the importance of stabilising the temperature and humidity conditions in the laboratory. Applying our technique to multiple plastic samples with known resistivity confirmed its accuracy. To evaluate its applicability to electrical tomography, we measured the potential distribution on a dry granite surface in response to an injected current using a simple 40-electrode array. The potential distribution measured by our procedure agreed well with that predicted by forward modelling, demonstrating the robustness of our procedure in array measurements, and thus indicating its potential applicability to tomographic measurements for a variety of targets even under severe conditions including the relative dryness of ambient humidity.https://doi.org/10.1186/s40623-021-01446-9Multi-point measurementSmall electrodeCurrent injectionVoltage measurementResistivity measurementContact resistance |
| spellingShingle | Takeshi Suzuki Ryokei Yoshimura Ken’ichi Yamazaki Naoto Oshiman A procedure for stable electrical measurements on a rock sample against high contact resistance as a prerequisite for electrical tomography Earth, Planets and Space Multi-point measurement Small electrode Current injection Voltage measurement Resistivity measurement Contact resistance |
| title | A procedure for stable electrical measurements on a rock sample against high contact resistance as a prerequisite for electrical tomography |
| title_full | A procedure for stable electrical measurements on a rock sample against high contact resistance as a prerequisite for electrical tomography |
| title_fullStr | A procedure for stable electrical measurements on a rock sample against high contact resistance as a prerequisite for electrical tomography |
| title_full_unstemmed | A procedure for stable electrical measurements on a rock sample against high contact resistance as a prerequisite for electrical tomography |
| title_short | A procedure for stable electrical measurements on a rock sample against high contact resistance as a prerequisite for electrical tomography |
| title_sort | procedure for stable electrical measurements on a rock sample against high contact resistance as a prerequisite for electrical tomography |
| topic | Multi-point measurement Small electrode Current injection Voltage measurement Resistivity measurement Contact resistance |
| url | https://doi.org/10.1186/s40623-021-01446-9 |
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