事件时间测量系统及其在绝对重力仪中的应用

Event-time Measurement System and Its Application in Absolute Gravimeters

关键词:  数字信号处理器  激光干涉  时间测量  绝对重力仪

Key words:  Digital Signal Processor (DSP)  Laser interference  Time measurement  Absolute gravimeter

摘要:

绝对重力仪通常采用真空腔中自由落体的方法，通过测量激光干涉条纹信号的过零时间来计算绝对重力加速度（g）。针对绝对重力仪的使用，依托电子计数法的基本原理，基于数字信号处理器（Digital Signal Processor，DSP）设计实现了事件时间测量系统，精确测量干涉条纹过零时间。首先介绍了事件时间测量的基本原理，然后具体介绍在以DSP为核心的硬件上的实现方法。根据理论计算和MATLAB数值仿真实验，评价系统测时误差以及对重力加速度测值的影响。最后分别通过硬件模拟实验和FG5X型高精度绝对重力仪上的对比实验进行验证。实验证明，该系统对重力加速度测量真值影响小于1μGal （1μGal=1×10-8m/s2），标准差影响小于5μGal。该系统体积小、成本低，尤其对于小型化、野外使用的绝对重力仪，完全符合其使用需求。

Abstract:

Laser interference is generally applied in the traditional free-falling absolute gravimeters, and the absolute gravitation acceleration (g) is measured by timing the zero-crossings of the interference fringe signal.An event-time measurement system based on Digital Signal Processor (DSP) is designed and realized for the application in absolute gravimeters.The principle of the event-time measurement is introduced, followed by the hardware implementation method.Time measurement errors and their effect on the gravity measurement are calculated both theoretically and from numerical software simulations with MATLAB, and verified by hardware simulated experiments and experiments using an FG5X high-precision absolute gravimeter.The results show that the effect on the true value of gravity acceleration measurement caused by the event-time measurement system is less than 1μGal (1μGal=1×10-8m/s2), and the effect on the standard deviation is less than 5μGal.The system has advantages of compact size, small volume and low cost, and meets the requirements of precision and portability, especially for field ready absolute gravimeters