This paper presents a design of a non – destructive testing device using eddy current technique. This device has a sinusoidal excitation source consisting of 4 frequencies which developed to operate with double-function eddy current sensors. The testing results are displayed on a LCD screen as a function of sensor’s output voltage to testing position, and user’s evaluation is based on shape of this signal. Experiments on several kind of tested specimen show that this device operates stably and can detect small surface or under-surface cracks. Concretely, it can detect under-surface cracks located at the distance of less than 1 mm from testing surface. For surface cracks, the device can detect defects featuring a depth of greater than 0.1 mm.
