Eliminating Inductive Coupling in Small-Loop TEM Through Differential Measurement with Opposing Coils
The small-loop transient electromagnetic method (TEM) refers to a system in which the coil frame length or diameter is less than 2 m. Due to the inductive effects of the multi-turn coils used for both transmission and reception, the induced electromotive force in the measuring coil increases, causin...
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MDPI AG
2025-01-01
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| author | Xinghai Chen Haiyan Yang Tong Xia Xiaoping Wu Shengdong Liu |
| author_facet | Xinghai Chen Haiyan Yang Tong Xia Xiaoping Wu Shengdong Liu |
| author_sort | Xinghai Chen |
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| description | The small-loop transient electromagnetic method (TEM) refers to a system in which the coil frame length or diameter is less than 2 m. Due to the inductive effects of the multi-turn coils used for both transmission and reception, the induced electromotive force in the measuring coil increases, causing a reduction in the decay rate and an extension of the shutoff time. This results in coupling between the primary and secondary fields in early-time signals, making them difficult to separate and creating a detection blind spot in the shallow subsurface. The opposing coil TEM transmission and reception method can significantly reduce early-time signal distortion caused by coil inductance. However, this approach is constrained by the physical symmetry of the coil dimensions, which makes it challenging to achieve balance in a zero-field space. By performing both forward and reverse measurements at the same location using the opposing coil setup and calculating the difference between the signals, the inductive coupling between coils at the measurement site can theoretically be eliminated. This eliminates the induced potential of the TEM signal, enhancing the induced electromotive force from the formation. As a result, more accurate resistivity values are obtained, detection blind spots are eliminated, and the resolution in shallow TEM exploration is improved. Field experiments were conducted to validate the method on both high-resistivity and low-resistivity anomalies. The results demonstrated that this method effectively identified a high-resistivity corrugated pipe at a depth of 1.2 m and two low-resistivity gas pipelines at a depth of 2 m, thereby essentially eliminating detection blind spots in the shallow subsurface. |
| format | Article |
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| institution | Kabale University |
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| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-7881d198f810496fa53c5a67b5b7c3b02025-01-24T13:47:53ZengMDPI AGRemote Sensing2072-42922025-01-0117225410.3390/rs17020254Eliminating Inductive Coupling in Small-Loop TEM Through Differential Measurement with Opposing CoilsXinghai Chen0Haiyan Yang1Tong Xia2Xiaoping Wu3Shengdong Liu4School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, ChinaSchool of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, ChinaSchool of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, ChinaSchool of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, ChinaSchool of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, ChinaThe small-loop transient electromagnetic method (TEM) refers to a system in which the coil frame length or diameter is less than 2 m. Due to the inductive effects of the multi-turn coils used for both transmission and reception, the induced electromotive force in the measuring coil increases, causing a reduction in the decay rate and an extension of the shutoff time. This results in coupling between the primary and secondary fields in early-time signals, making them difficult to separate and creating a detection blind spot in the shallow subsurface. The opposing coil TEM transmission and reception method can significantly reduce early-time signal distortion caused by coil inductance. However, this approach is constrained by the physical symmetry of the coil dimensions, which makes it challenging to achieve balance in a zero-field space. By performing both forward and reverse measurements at the same location using the opposing coil setup and calculating the difference between the signals, the inductive coupling between coils at the measurement site can theoretically be eliminated. This eliminates the induced potential of the TEM signal, enhancing the induced electromotive force from the formation. As a result, more accurate resistivity values are obtained, detection blind spots are eliminated, and the resolution in shallow TEM exploration is improved. Field experiments were conducted to validate the method on both high-resistivity and low-resistivity anomalies. The results demonstrated that this method effectively identified a high-resistivity corrugated pipe at a depth of 1.2 m and two low-resistivity gas pipelines at a depth of 2 m, thereby essentially eliminating detection blind spots in the shallow subsurface.https://www.mdpi.com/2072-4292/17/2/254opposing coilcoil reversalinductanceblind spot elimination |
| spellingShingle | Xinghai Chen Haiyan Yang Tong Xia Xiaoping Wu Shengdong Liu Eliminating Inductive Coupling in Small-Loop TEM Through Differential Measurement with Opposing Coils Remote Sensing opposing coil coil reversal inductance blind spot elimination |
| title | Eliminating Inductive Coupling in Small-Loop TEM Through Differential Measurement with Opposing Coils |
| title_full | Eliminating Inductive Coupling in Small-Loop TEM Through Differential Measurement with Opposing Coils |
| title_fullStr | Eliminating Inductive Coupling in Small-Loop TEM Through Differential Measurement with Opposing Coils |
| title_full_unstemmed | Eliminating Inductive Coupling in Small-Loop TEM Through Differential Measurement with Opposing Coils |
| title_short | Eliminating Inductive Coupling in Small-Loop TEM Through Differential Measurement with Opposing Coils |
| title_sort | eliminating inductive coupling in small loop tem through differential measurement with opposing coils |
| topic | opposing coil coil reversal inductance blind spot elimination |
| url | https://www.mdpi.com/2072-4292/17/2/254 |
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