LRS Micro-g LaCoste FG5, Manual, Page: 10 / 149

Concept and History of the FG5
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1.3. FG5 Design Features
The FG5 incorporates a number of significant advancements in design which
reduce or eliminate systematic errors identified in the earlier versions, and which
make the FG5 easier to use. These improvements are:
• An inline interferometer beam path which eliminates systematic errors
from tilt-induced path length changes.
• Complete redesign of the Superspring, a device for providing an inertial
mass that contains a retroreflective corner cube. The new Superspring has
improved performance, and at the same time greatly reduced size. The drift
problems of earlier designs have been reduced substantially.
• Completely new tripod design, which supports the test chamber, for extra
stability. The tripod is now built symmetrically with respect to the drop line.
• Improvements to the electronics reflect new technology and make the
instrument smaller and easier to use.
• This absolute gravimeter is designed to work with a new rugged iodine-
stabilized laser system (WEO model 100) traceable to the BIPM.
• The system controller has been updated to an Intel-based personal
computer with a standard language interface. The decision to use standard
PC technology has allowed the FG5 to offer more computing power while
reducing the size of the instrument.
• “g”, a user-friendly, Windows©-based, full-featured software program
takes interferometer data and environmental data. This software provides an
immediate value for the local gravity in real-time. The program is also a full-
featured post-processing software program that allows complete ability to
vary data analysis procedures and to vary environmental corrections.
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