Patent ID: 7508221

Claim:
Wall detector for detecting an object ( 3 ) embedded in a substrate ( 2 ), comprising a detection antenna ( 5 ) for introducing broadband, high-frequency alternating electric fields ( 9 ) of a mean measurement frequency (f M ) in the substrate ( 2 ); a measurement system ( 6 ) connected to the detection antenna ( 5 ) for measuring a delayed interaction of the alternating fields ( 9 ) with the object ( 3 ); a calculation device ( 7 ) for detecting the object ( 3 ) based on a measurement signal and for determining an associated depth information; and a permittivity measurement device ( 10 ) with at least one auxiliary potential plate ( 11 ) for measuring a permittivity measurement signal of the substrate at a permittivity measurement frequency (f p ) that is lower than the mean measurement frequency (f M ), with the permittivity measurement device ( 10 ) performing a permittivity determination step ( 18 ) in which a relative permittivity ∈ r of the substrate ( 2 ) is determined for the measurement frequency (f M ) by the calculation device ( 7 ) using a stored material model ( 14 ) described by a relaxation in the permittivity determination step ( 18 ).