飞行时间的计数式测量及其在电缆故障检测中的应用

Counting Method for Time-of-flight Measurement and its Application in Cable Fault Test

利用1个独立时钟和1个数字计数器实现飞行时间的计数式测量。采用对多次重复测量计数值取平均的方法,提高时间测量的精度。将这种计时方法与时域反射仪(Time domain reflectometry,TDR)原理相结合,设计了一种电缆故障定位检测系统。利用单片机MSP430F149产生周期性测试信号,用8 MHz时钟和8位数字计数器完成了测试信号计时。试验结果证明:通过将30 000次测量结果取平均,可以使计时精度提高到1 ns以上。应用这种测试方法制作的样机,操作简单,易于携带,试验证明其测量误差小于0.15 m.

An independent clock and a digital counter were used for measuring the time of flight in a counting way.The accuracy of timing was improved by averaging a number of repetitive measurement results.A cable fault locator was designed combining the proposed timing method with time domain reflectometry （TDR）principles.A microcontroller MSP430F149 was used to generate a periodic test signal.The process of timing,is implemented by an 8 MHz clock together with an 8-bit digital counter.Experimental results show that,by averaging results of 30 000 repetitive measurements,the timing accuracy is refined to better than nanosecond.A prototype applying this test method is manufactured,which is easy to operate and carry.Experimental results prove that its measurement error is less than 0.15 m.