Designed by Johann Solomon Christoph Schweigger (1779-1857), professor of chemistry at the Le Halle University, who presented it on 16 September 1820 before the Natural Philosophy Society of that city, the apparatus consists of a coil of copper wire wound on a rectangular wooden frame (29 cm x 6.5 cm), in the centre of which a large magnetic needle lying on a special pointed stand is free to rotate. When electricity flows through the coil, since the electricity passes through all the turns in the same direction, they exert equal and concordant actions on the needle and it thus undergoes a far stronger action than would be produced by a single turn.
From this derives the name of multiplier attributed to it later on, but Schweigger continued to call it simply a duplication apparatus.
The working principle is that of a mobile needle galvanometer. With the addition of a graduated circle the multiplier becomes a true, albeit primitive, galvanometer.