Usage/History: The pointer galvanometer is a sensitive
instrument for measuring current. It consists of a magnet coil
with an attached needle suspended between the poles of a magnet.
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 example here is a null instrument, that is
it is designed to be used in circuits where two currents are
balanced against each other, i.e. with a Potentiometer or a Wheatstone
Bridge, until the meter reads zero.
Some contemporary/early descriptions of the Galvanometer
and its use are provided below:
Description: The instrument is housed in a 4 1/2 x
2 3/4 x 2 3/4 in Bakelite case with LEEDS & NORTHRUP CO.
/ PHILADEPHIA / MADE IN U. S. A. in raised letters within a rectangular
depression on the case front. The meter display is in a 2 1/2
x 1 3/4 x 1 inch high wedge shape steel container mounted on
top of the case. A 1/2 x 1 1/4 inch window in front exposes the
-10-0-+10 graduated scale and pointer. Two brass binding posts
are placed on the opposite top rear corners of the case.
