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 1×10-11 m/√Hz. We describe the instrument construction and demonstrate low noise operation with a noise floor upper bound of 5.7×10-9rad/√Hz at 10 mHz and 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. © 2014 AIP Publishing LLC.
Dergachev, V., Desalvo, R., Asadoor, M., Bhawal, A., Gong, P., Kim, C., Lottarini, A., Minenkov, Y., Murphy, C., O'Toole, A., Peña Arellano, F. E., Rodionov, A. V., Shaner, M., & Sobacchi, E. (2014). A high precision, compact electromechanical ground rotation sensor. Review of Scientific Instruments, 85(5), 054502-1 - 054502-13. https://doi.org/10.1063/1.4875375