D'Arsonval Galvanometer ca 1900
This excellent example of a D’Arsonval Galvanometer was made by the Central Scientific Company of Chicago and is in excellent condition. The name of CENTRAL SCIENTIFIC COMPANY, CHICAGO is pressed into the wood unlike their later instruments where a name plate is affixed to the instruments.
I am indebted to Thomas B. Greenslade, Jr., Professor Emeritus of Physics, Kenyon College for his allowing me to copy much of this text from his outstanding website on antique scientific instruments.
“Jacques D'Arsonval (1851-1940) was a director of a laboratory of biological physics and a professor of experimental medicine ... In the D'Arsonval-Deprez design the coil has many turns of fine wire, and is suspended by flat ribbon of wire which serves as one lead-in wire. The connection to the lower end of the coil is provided by a light, helical spring that provides the restoring torque. The electro-magnetic torque is greatest when the magnetic field lines are perpendicular to the plane of the coil; this condition is met for a wide range of coil positions by placing the cylindrical core of soft iron in the middle of the magnetic gap, and giving the magnet pole faces a concave contour. Since the electro-magnetic torque is proportional to the current in the coil and the restoring toque is proportional to the angle of twist of the suspension fiber, at equilibrium the current through the coil is linearly proportional to its angular deflection. This means that the galvanometer scales can always be linear, a great boon to the user.” To enlarge view, click on photos.
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Price: Sold
