Infrared lock-in excitation technology based on digital power control

To improve the integration level and performance of modulated heat excitation source, a new digital power control technology was developed for application of lock-in thermography in NDT. Silicon controlled rectifier(SiCR) was used as a power output controlling unit, and a relationship between SiCR's control angle and output power was also obtained. Taking the sinusoidal signal as the excitation source, the changing rule of control angle over time was achieved by using numerical calculation while the control algorithm and implementation method of the conduction angle were designed based on digital micro processing circuit. The experimental platform was thus built up and the comparison experiments were carried out. The results show that the present approach can gain higher precision of power control, better fidelity of thermal waveform and preferable equipment in structure and size. Moreover, its electromagnetic safety can meet the relevant requirement. Therefore, better results can be expected by using this method in the infrared lock-in thermography.