This article focuses on the developments in electromagnetism during the early 19th century. The discovery of electromagnetism by Hans Christian Ørsted, in 1820, was a gamechanging event that opened perspectives into the deep understanding of physics and fundamental technical applications. In this article, the principles to measure and quantify electric current are given particular attention. Several scientists, including Schweigger, Poggendorff, Nobili, and Pouillet, contributed to the development of an instrument toward this purpose, the galvanometer. Here, we put special emphasis on research by Johan Jacob Nervander, whose tangentbussol, presented to l'Institut de France, in spring 1834, and later published in <italic>Annales de Chimie et de Physique</italic>, was a significant milestone in the instrumentation of electrical engineering.