Astatic adj. (Magnetism) Having little or no tendency to take a fixed or definite position or direction: thus, a suspended magnetic needle, when rendered astatic, loses its polarity, or tendency to point in a given direction.
Astatic pair (Magnetism), a pair of magnetic needles so mounted as to be nearly or quite astatic, as in some galvanometers.
... instrument is capable of making a deflection of one division of 1/50 inch upon a scale placed at a distance of a little more than a yard, with the current produced by one daniell of 10 ohms. This is a degree of sensitiveness that cannot be obtained with any of the astatic instruments known up to the present. By regulating the needles properly, a greater degree of sensitiveness may be attained, but then the duration of the needles' oscillation becomes too great. ... — Scientific American Supplement, No. 492, June 6, 1885 • Various
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