Magnetically coupled suspension for self:compensating balances - has bar magnets suspended in coils stabilised by proportional integral controller

摘要

The magnetically-coupled suspension for precision weighing instruments of the self-compensating type, consists of a bar marnet (2) suspended from the balance load arm (1), the lower part of the magnet being surrounded by a control winding (11). A second control winding surrounds the upper part of an evacuated vertical tube in which the specimen tray (4) is suspended from a second bar magnet (3). The vertical separation between the adjacent ends of the magnets is detected by a photo-electric system (6) (8). The detector output operates a proportional-integral controller (10) (13) whose output signals are fed to the upper and lower control windings respectively. Any vertical disturbing forces are counter-balanced by the superimposed control currents.