A sensor (5, 30, 60), comprising: a first electrode (6, 31, 61); a second electrode (8, 32, 62); an insulator (10, 33, 63) positioned between the first electrode (6, 31, 61) and the second electrode (8, 32, 62) and configured to receive conductive abrasion powder contained in a detection region and attracted onto the insulator (10, 33, 63) by the first electrode (6, 31, 61) which is configured to also serve as a first magnet or by a first magnet (7, 34, 64) positioned between the first electrode (6, 31, 61) and the second electrode (8, 32, 62); a sensing unit for sensing a change in electrical resistance between the first electrode (6, 31, 61) and the second electrode (8, 32, 62) caused by the conductive abrasion powder; and at least one second magnet positioned within the detection region and configured to attract the conductive abrasion powder contained in the detection region, wherein the at least one second magnet is spaced apart from the first electrode (6, 31, 61), the second electrode (8, 32, 62), and the insulator (10, 33, 63), characterized by further comprising: a sensitivity adjusting unit for adjusting attraction of the conductive abrasion powder to change sensitivity, wherein the at least one second magnet comprises a plurality of second magnets having different attractive powers for attracting the conductive abrasion powder, and wherein the sensitivity adjusting unit is formed of the plurality of second magnets. a first electrode (6, 31, 61); a second electrode (8, 32, 62); an insulator (10, 33, 63) positioned between the first electrode (6, 31, 61) and the second electrode (8, 32, 62) and configured to receive conductive abrasion powder contained in a detection region and attracted onto the insulator (10, 33, 63) by the first electrode (6, 31, 61) which is configured to also serve as a first magnet or by a first magnet (7, 34, 64) positioned between the first electrode (6, 31, 61) and the second electrode (8, 32, 62); a sensing unit for sensing a change in electrical resistance between the first electrode (6, 31, 61) and the second electrode (8, 32, 62) caused by the conductive abrasion powder; and at least one second magnet positioned within the detection region and configured to attract the conductive abrasion powder contained in the detection region, wherein the at least one second magnet is spaced apart from the first electrode (6, 31, 61), the second electrode (8, 32, 62), and the insulator (10, 33, 63), characterized by further comprising: a sensitivity adjusting unit for adjusting attraction of the conductive abrasion powder to change sensitivity, wherein the at least one second magnet comprises a plurality of second magnets having different attractive powers for attracting the conductive abrasion powder, and wherein the sensitivity adjusting unit is formed of the plurality of second magnets. a sensitivity adjusting unit for adjusting attraction of the conductive abrasion powder to change sensitivity, wherein the at least one second magnet comprises a plurality of second magnets having different attractive powers for attracting the conductive abrasion powder, and wherein the sensitivity adjusting unit is formed of the plurality of second magnets.