| 摘要 |
A sensing apparatus for detecting an interface between first and second materials (20), each have a different dielectric loss factor, disposed in a stratified manner in a volume of materials having a predetermined (36-1, 36-2) depth comprises a length of transmission line (20) having an inner conductor surrounded by a dielectric material and a shielding conductor (30). The transmission line (20) may be coaxial or planar in form. The transmission line of the sensing apparatus has a predetermined number of sub-lengths of inner conductor exposed along the length of the transmission line. Adjacent sub-lengths of exposed inner conductor are separated by shielded sub-lengths (38). The exposed sub-lengths of inner conductor (30) may be bare or surrounded by the dielectric layer. In use, the sensing apparatus having the exposed sub-lengths of inner conductor is excited by a radio frequency signal at a predetermined amplitude and is inserted into the volume of material. The total attenuation in amplitude or the change in attenuation is proportional to the number of exposed inner conductor (30) sub-lengths (38) (i.e., total length of the inner conductor (30)) exposed to the first material and provides an indication as to the location of the interface between the first material and the second material.
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