LRS Micro-g LaCoste FG5, Manual, Page: 28 / 149

Design: Components and Function
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2.5.3.SUPERSPRING CONTROLLER
The purpose of the electronic and mechanical systems for the superspring is to
isolate the reference mass from any vertical motion of the instrument in order to
keep the path length of the test beam constant. Three systems provide coarse
and fine adjustment of the spring support structure: a motor attached to the top
of the mainspring, a
linear actuator coil and magnet system, and an aneroid
wafer assembly . A controller circuit board drives the motor and the coil and
magnet system, while the aneroid wafer assembly responds automatically to
temperature changes.
A sphere detector system similar to the one used in the Dropping Chamber
provides information on the position of the reference mass relative to the
mainspring support system. An infrared LED and a photo detector are mounted
opposite each other inside the mainspring support housing. A sphere attached
to the bottom of the mass focuses the light from the LED onto the detector, which
transmits the resulting signal to a sphere signal preamplifier.
The zero-position of the sphere on the test mass can be adjusted by moving the
top of the main spring with a small DC motor with a very large gear ratio for fine
control.
The main servo electronics control, the coil-magnet forcer, moves the main
spring support in such a way to keep the main spring length constant. This active
servo effectively weakens the main spring, synthesizing a long period isolation
device. The active period of the superspring is nominally about 60 seconds.
2.5.4.LASER CONTROLLER
The laser controller supplies power and enables operator control for the WEO
Model 100 Iodine stabilized laser or the Micro-g Solutions Model ML-1
frequency/intensity stabilized laser. See Chapter 3 for setup and operation.
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