Crack detection device and method therefor

A crack detection device for detecting a crack in a structure, comprising:

• a sensor unit that has a three-layer structure of conductor-insulator-conductor and is attached to the structure;
• a frequency characteristics acquisition unit that sweeps a predetermined frequency range to acquire a plurality of frequencies at which an impedance of the sensor unit is maximum or minimum;
• a processor;
• and
• a non-transitory computer readable medium having stored thereon a crack position table in which a relationship between crack positions and frequency shift directions is recorded, the non-transitory computer readable medium also having stored thereon executable code that, when executed by the processor, causes the processor to function as:
• a crack presence/absence determination unit that determines presence or absence of a crack based on a nonuniformity of the plurality of frequencies;
• and
• a crack position detection unit that, when the crack presence/absence determination unit determines that there is a crack, takes a difference between two frequencies acquired by the frequency characteristics acquisition unit to determine a sign, and then refers to the crack position table in accordance with the sign to detect a crack position.