Research On Time Measurement In Absolute Gravimeter

Earth gravitational field which reflects lots of physical information,such as the density distribution on the earth, earth’s rotation is the basicinformation resource. Absolute Gravimeter is one of the most importantinstruments to obtain high-precision data of gravitational field. At present,in the absolute gravity measuring system, phase difference can be mainlyobtained by free falls. The falling time and the displacement of object canbe gained through applying laser interference principle to measurement.In the end, acceleration of gravity g can be calculated. With thedevelopment of fine mechanics process，optics，vacuum，electronictechnology, measurement method and error discipline, the precision ofabsolute gravimeter will be improved increasingly, the latest FG5hasreached up to1×10^-8m/s2.In the system of gravimeter, many factors including the stability oflaser frequency, the vacuum chamber, gravity gradient and periodcalculation of interference fringe may influence the precision of absoluteGravity. Particularly, high-precision time measurement has been widelyused in scientific research, national defense and industry field. With therapid development of the information-based society, high-precision timemeasurement will play an increasing important role in many otherresearch fields. At present, some developed countries have taken theleading position in the high-precision measurement technology. However,our country is still at development stage, so it is necessary to research thetechnology on high-precision time measurement.This paper introduces the principle and methods of the AbsoluteGravimeter used in measuring the distance of free falling objects and itscorresponding time intervals. The importance is that applying high-precision time measurement chips TDC502to improving the precision oftime measurement, and combining the large-scale integration of digitaldesign, the precision of gravimeter system will be improved.