Disclosed is a system and method suitable for calibrating a phased array system configured to inspect square bars. A square bar is provided with an array of parallel linear notches across the full range of the testing surface of the square bar for this calibrating purpose. The square bar is passed through the probe in probe's passive direction during the calibration. The phased array system is adjusted and calibrated so that the echo amplitude for each inspection channel of the phased array probe received from each notch is substantially equal. Then a known flaw with a typically expected flaw's size and shape is created on the same testing surface so that the system's sensitivity is adjusted using the amplitude of the echo signal from the known flaw as a baseline.