crystal transducer การใช้

• His solution used a column of piezo crystal transducers ( a combination of speaker and microphone ) at either end.
• James F . McNulty ( U . S . radio engineer ) of Automation Industries, Inc ., then, in El Segundo, California, an early improver of the many foibles and limits of this and other nondestructive testing methods, teaches in further detail on ultrasonic testing in his U . S . Patent 3, 260, 105 ( application filed December 21, 1962, granted July 12, 1966, titled  Ultrasonic Testing Apparatus and Method ) that  Basically ultrasonic testing is performed by applying to a piezoelectric crystal transducer periodic electrical pulses of ultrasonic frequency.