Abstract
A tiltmeter has been developed at the Institute of Physics of the Earth of the Russian Academy of Sciences as the regular equipment for geophysical observatories and other observation posts. The tiltmeter is intended for relative measurement of tilts of a terrestrial surface in two mutually perpendicular directions for the purpose of studying tidal deformations, research of modern earth movements, research of harbingers of earthquakes in the form of abnormal inclinations, and also deformations of the bases and parts of large engineering constructions. The tiltmeter which has been developed possesses record-breaking high precision 0.0001 arc sec. in a range of measurement +/-2 arc sec.; thus it has extremely high long-term tool stability (tool drift of "zero" no more +/-1 arc sec. per year). The combination of these major technical characteristics makes this tiltmeter an outstanding achievement in the field of geophysical instrument making. Sensor action is based on the principle of a vertical pendulum. In the sensor design a metal pendulum (length about 100 mm) is suspended on an elastic suspension over the ceramic part fixed on the case. The pendulum has a natural period of 0.6 seconds and air damping. It is isolated from the case and together with a ceramic part forms the differential two coordinate measuring condenser. On a ceramic casing four metal plates serving as facings of the measuring condenser are fixed. At an inclination of the sensor case the pendulum moves with respect to the condenser facings proportionally, making an inclination from these axes. As a result the measuring condenser records signals proportional to the angle of slope of the sensor on its sensitivity axes ?N-S? and ?E-W?.