Because of poor performance of acoustic penetration in fruit ultrasonic testing, it is difficult to get the effective fruit characteristic parameters. An ultrasonic testing circuit system is designed to solve this technical bottleneck. In this system, AT89S52 is taken as the circuit control unit to control the MOSFET half-bridge to modulate the high voltage (450 V) direct current from boosting DC/DC to become high-voltage square wave signal (ranging from 3 μs to 12 μs). And then, the signal is used to excite the ultrasonic transducer, whose sensitive element is thick wafer (whose R/H = 2. 59) piezoelectric ceramic, to produce high-energy low-fre quency ultrasonic. The circuit system has been successfully applied to the detection of the velocity of sound in the apple to verify its effectiveness. This detection system can provide technical reference for the ultrasonic tes ting of characteristic parameters, quality and damage of fruit.%针对水果超声检测时存在声波穿透性能差,致使无法实现水果特征参数有效检测的问题,设计了一种用于水果超声检测的电路系统,用于解决这一技术瓶颈.该系统中,换能器采用厚径比为R/H=2.59的厚圆片压电陶瓷作为敏感元件,通过AT89S52控制的MOS管半桥对DC/DC升压转换电路产生的幅值为450 V的直流高压进行调制,将得到的高压方波信号(可调脉宽范围3～12 μs)对换能器进行激励,以产生高能低频的超声波.通过将该电路系统应用于苹果中声速的测定,验证了该电路系统的有效性.该检测系统可为水果特征参数、水果品质以及损伤的超声检测提供技术参考.
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