Usage/History: The reflecting galvanometer is a sensitive
instrument for measuring current. It consists of a magnet coil
with an attached mirror suspended between the poles of a magnet
by a thin gold ribbon above and a coiled gold wire below. When
an electric current is introduced into the magnet coil it induces
a magnetic field, causing the coil to rotate in proportion to
the current. The mirror allows the user to see very small deflections,
and thus to measure very small currents, by observing a distant
reflected scale (one meter or more away) through a telescope.
The instrument is mounted on an optional leveling base of cast
iron.
Some contemporary/early descriptions of the Galvanometer
and its use are provided below:
Description: L&N Type P, current, student grade
moving coil reflecting galvanometer, serial number 102521. The
meter consists of a 7 1/8 x 4 5/8 x 7/8" magnet covered
by a bronze plate with a center 1 3/4 x 3 3/8" window and
with a hollow suspension post of nickel plated brass (4 1/4 x
3/8") on top. The L&N logo is in polished raised letters
against a black painted background, with raised polished borders
around the edge and the window. The coil is stabilized with wax,
the mirror is 5/8" dia. The meter is mounted on 6 1/4 x
9 x 3/4" mahogany backboard with two nickel plated brass
hangers at the top, two black painted telescope arm brackets
on the sides, two Bakelite binding posts at the bottom on either
side of a leveling screw, a manufacturers label on the bottom
edge and a brass Humboldt S-T-C tag (2120) on the lower right
hand corner. The leveling screw is a replacement from a more
recent model of the same instrument. The tripod galvanometer
base is of heavy cast iron with a japanned finish. There are
three brass & Ebonite leveling screws.
