A cartridge type sensor head was fabricated to detect the level of corrosion in steel cables with consistent or varying cross sections by assessing the LMA (Loss of Metallic Area) damage. Two coil sensor cartridges were made to cater to cables with up to 70mm and 150mm. The developed system was verified through lab experiment using a tapered steel cable specimen, and through a field test conducted in cable bridge. The result showed that the developed system is capable of assessing a cable with varying cross section.