LaCoste & Romberg gravity meter : System analysis and instrumental errors

Although the LaCoste & Romberg (L&R) gravity sensor can be used with great care to collect 1-μGal data, the sensor has a thermodynamic noise limit of 0.012 μGal—about two orders of magnitude below the present measurement precision. Hence, thermodynamic noise is not the limiting factor, and there is significant room for improvement by bringing the other perturbing influences under adequate control. We do not see any fundamental instrumental limitations to substantially improving measurement accuracy at least down to 0.1 μGal. We have improved the noise level, stability, and reliability of the L&R borehole gravity meter sensor, with the goal of reducing the total system noise to below 1 μGal. In the process of these improvements, we made several fundamental observations about noise sources within the L&R sensor, particularly related to thermal noise, electronic noise, sources of mechanical and electrical rectification errors, temporal mass variations, and instrument tares and drift. It has always been assum...