Patent ID: 7148703

Claim:
A sensor for finding a feature of a structure behind a surface comprising: a first plate having a first capacitance and adapted for forming a first capacitor with the structure; a second plate having a second capacitance and adapted for forming a second capacitor with the structure; a first measurement circuit coupled to the first plate, the first measurement circuit measuring a first capacitance value of the first capacitor; a second measurement circuit coupled to the second plate, the second measurement circuit measuring a second capacitance value of the second capacitor; and a comparison circuit coupled to the first and second measurement circuits, the comparison circuit generating a ratio of the first and second capacitance values to determine a lateral location of the feature relative to the plates and comparing one of the first or second capacitance values to a first threshold to determine a depth of the feature relative to the surface, further comprising threshold circuitry coupled to first and second measurement circuits, the threshold circuitry determining whether the first and second capacitance values are above a second threshold to determine if the feature is deep.