| 摘要 |
PROBLEM TO BE SOLVED: To directly measure a variation without being covered with an AD conversion quantization error, in an instrument for measuring the variation of a surface potential difference caused by a difference in frequencies of an alternating current impressed between two points in the ground in order to specify a substance containing in the ground and to specify precisely a position and a depth thereof. SOLUTION: The current impressed to the ground is constituted of a sum of two sine waves having the first and second frequency components, and a signal used in synchronization detection is constituted of a difference between the sine waves having the first and second frequency components. COPYRIGHT: (C)2006,JPO&NCIPI |
