Description: Moving coil galvanometer used as a current balance.

Caption: The instrument was designed for direct current and for this reason has coils made from copper ribbon. It has two fixed coils and one moveable coil. is unsigned but is clearly a James White & Company built nachiner with easily recognisable standard components.

Introduction: This is a rack form of the single arm deka-ampere balance. This is a form of current balance related to GLAHM 105028 with the riders (removable weights) acting directly on the moving coil rather than the end of the balance arm. The range of the instrument can be altered by the adjust ment of the levers that engage or disengage the riders.

Background: It was probably intended to be a prototype or preproduction model. However, the system has inherant built in errors such as temperature and magnetic field variation. Kelin overcame these difficulties by using two sets of fixed coils, beween which he place two moving coils at either end of a balance beam pivoted at its centre. The coils wre wired in opposition so that any errors were atomatically cancelled out.

Historical Context: Design of the first moving coil galvanometer - Who: Sturgeon, William (1783-1850) English physicist and inventor

Historical Context: Design of the first moving coil galvanometer by Sturgeon - When: 1826

Historical Context: Design of the first moving coil galvanometer by Sturgeon at East India Company Royal Military College - Where: Addiscombe, Surrey, England

Historical Context: Design of this form of moving coil instrument by Lord kelvin - When: circa 1887 - Where: Glasgow, Scotland - Who: Thomson, William, Professor (1824-1907) Sir William Thomson from 1866 and Ist Baron Kelvin of Largs from 1892 better known as Lord Kelvin

Historical Context: Discovery of the electromagnetic effect - Who: Oersted, Hans Christian (1777-1851) Danish physicist

Historical Context: Discovery of the electromagnetic effect by Oersted - When: 1819 - Where: Copenhagen, Denmark

Historical Context: Manufacture - When: circa 1887 - Where: 16, 18, and 20 Cambridge Street, Glasgow, Scotland - Who: James White & Company

Historical Context: Reintroduction of the moving coil galvanometer as a measuring instrument by d'Aesonval - When: 1882

Historical Context: Reintroduction of the moving coil galvanometer as a measuring instrument by d'Arsonval - Where: Paris, France

Historical Context: Reintroduction of the moving coil galvanometer as a measuring instument - Who: Arsonval, Jacques-Arsene d' (1851-1940)

Historical Context: Use of the moving coil galvanometer movement as a telegraph signal detector - Who: Thomson, William, Professor (1824-1907) Sir William Thomson from 1866 and Ist Baron Kelvin of Largs from 1892 better known as Lord Kelvin

Historical Context: Use of the moving coil galvanometer movement as a telegraph signal detector by Lord Kelvin - When: circa 1860 - Where: Glasgow, Scotland

Historical Context: Used at the Gilbert Scott Buildings in research and lecture demonstrations in the Department of Natural Philosophy - Who: Thomson, William, Professor (1824-1907) Sir William Thomson from 1866 and Ist Baron Kelvin of Largs from 1892 better known as Lord Kelvin

Historical Context: Used in research and lecture demonstrations in the Department of Natural Philosophy now called the Department of Physics and Astronomy - Where: Natural Philosophy Lecture Theatre, Gilbert Scott Building, University of Glasgow, University Avenue, Glasgow, Scotland

Historical Context: Used in the Gilbert Scott B'lding by Prof. William Thomson in the Department of Natural Philosophy now called the Department of Physics and Astronomy - When: circa 1883