GRAVITY VARIOMETER (from the Latin word "vario", which means "I modify", and Greek word "metreo", which means "I measure" * EN: gravity variometer; DE: Gravitationvariometer; FR: variometre gravimetrique; ES: variymetro gravimetrico; RU: вариометр) is the instrument for the measurement of the second derivatives of the potential of the gravitational field, which are characterizing the variation of the force of gravity along the horizontal direction, and the curvature of the equipotential surfaces.
Variometers are used for the detailed research of the gravitational field within the regions with the great horizontal gradients, for the exploration and detailing of mainly the iron ore and polymetallic deposits.
They name the variometers, which are measuring only the gradients of the gravitational field, as the gradiometers. The major part of the variometer is the torsion balance, which is comprising the light horizontal or inclined rod ("beam"), which is suspended on the thin metallic wire, to the ends of which there are attached the loads, which are located at the different levels. Within the uniform gravitational field, the wire of the beam, which has calmed itself, is fully untwisted, while within the non-uniform field, the wire is twisted at the certain angle, depending on the amount of the variation for the acceleration of the force of gravity. The determination of the deflection for the beam from the initial untwisted position is conducted for several azimuths (at least three). The variometers have the photorecording auxiliary device, and the device for the automatic transition from one azimuth to another. The time of the measurement for one azimuth is 20-40 minutes. The precision for the determination is 2^-5 eotvoses (1 eotvos = 10^-9 seconds ^ -2).
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