We present a mechanical rotation sensor consisting of a balance pivoting on a tungsten carbide knife edge. These sensors are important for precision seismic isolation systems, as employed in land-based gravitational wave interferometers and for the new field of rotational seismology. The position sensor used is an air-core linear variable differential transformer with a demonstrated noise floor of

${1}{\,\times\, 10^{-11}}\textrm { m}/\sqrt{\textrm {Hz}}$
1×10−11m/ Hz ⁠. We describe the instrument construction and demonstrate low noise operation with a noise floor upper bound of
${5.7}{\,\times\, 10^{-9}}\textrm { rad}/\sqrt{\textrm {Hz}}$
5.7×10−9 rad / Hz at 10 mHz and
${6.4}{\,\times\, 10^{-10}}\textrm { rad}/\sqrt{\textrm {Hz}}$
6.4×10−10 rad / Hz at 0.1 Hz. The performance of the knife edge hinge is compatible with a behaviorur free of noise from dislocation self-organized criticality.

Topics
Noise floor, Linear variable differential transformers, Clinometer, Sensors, Seismology, Gravitational waves, Interferometry, Gravitational force, Dynamical systems, Transition metal carbides
© 2014 AIP Publishing LLC.
2014
AIP Publishing LLC
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