The tangent galvanometer of Johan Jacob Nervander

• Published in: IEEE instrumentation & measurement magazine Vol. 11; no. 3; pp. 16 - 23
• Main Authors: Venermo, J., Sihvola, A.
• Format: Magazine Article
• Language: English
• Published: New York, NY IEEE 01.06.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Coiling; Conductors; Current measurement; Deviation; Electric current; Electric variables measurement; Exact sciences and technology; Galvanometers; General equipment and techniques; Geomagnetism; Inductors; Instrumentation; Instruments; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Jacobian matrices; Law; Magnetic field measurement; Needles; Physics; Servo and control equipment; robots; Tangents; Wire; Galvanometers
• ISSN: 1094-6969; 1941-0123
• DOI: 10.1109/MIM.2008.4534374

J.J. Nervander designed the more- sensitive tangent galvanometer in 1834, which led to a great improvement in precise measurements of electric current. Because of its ingenuous coiling arrangements, Nervander was able to use the tangent busol to prove the validity of the law that the tangent of the deviation angle of the needle of the tangent-bussol is proportional to the electric current flowing through its coil. Exploitation of the tangent law provided a way of measuring and comparing currents. The increased sensitivity of the galvanometer was a result of the uniformity of the current-created magnetic field over the cylindrical volume inside the coils. This allowed the use of a long magnetic needle. The reconstructed galvanometer operates with a short needle. For the reconstructed galvanometer, the tangent law is valid up to deflection angles more than 50deg; Nervander reported acceptable deviations only up to 30deg.