In this paper a signal processing method is proposed for the ultrasonic inspection based on the acoustic impedance called Peniel. This method has a low computational complexity which make it suitable for portable devices of small size. This method analyzes the acoustic impedance behavior of the sample inspected or process monitored to recognize defects or process evolution. Ultrasonic sensors based on the acoustic impedance measurement have important applications in industrial sectors such as energy, chemicals, aerospace, automobile, food, construction, among others. In this work is illustrated the implementation of the method for material identification using a microcontroller and its adaptation to recognize defects in bonded joints.