[en] A differential type eddy current probe is used to detect defects that exist in the heat exchanger tube. Every probes produced have their own size and frequency values depending on the purpose and functionality of the probe. In this study a probe is fabricated by winding wire in solenoid shape. When current flows through it, magnetic field is produced surrounding it. In this study, effects of two probe parameters namely numbers of coil, N and the diameter of the copper wire, d were investigated. Diameters of copper wire chosen were 0.10 mm, 0.12 mm and 0.13 mm. These wire were wound around the body probe with diameter of 15 mm. For each wire diameter, the wire is wound with numbers of wound of 30, 50 and 70. The fabricated probes will be tested on the Stainless Steel 304 calibration tube with the nominal outside diameter of 19.07 mm and thickness of 1.24 mm. It contains seven artificial defects that are purposely introduced in accordance to ASME V Article 8. Performance of the probe were evaluated based on the separation angle of signals obtained from 100 % wall lost and that obtained from a 20 % of side drill hole defect. The probe was used in conjunction with a special instrument known as RD Tech MS 5800. This special instrument is specifically used for data recording and storing as well as for analysing signals obtained during the test. (author)