Usage: 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.
This instrument was used by students in the physical/analytical
chemistry laboratory at HSU for sensitive measurements in conjunction
with the L&N K-3 Potentiometer.
Some contemporary/early descriptions of the Galvanometer
and its use are provided below:
Description: The instrument is 9" high with the
base 5" in diameter. This particular instrument has a flat-black
finish on the aluminum case, a heavy Bakelite base, and a chrome-plated
knurled head for the clamping and adjusting shafts. A 70,000
Ohm critical damping shunt resistor is in place across the input.
The mirror in this instrument is 3/8" dia, as opposed to
the 1/2" mirror in the lowere sensitivity instruments described
in the Cenco catalogs below. The serial number, 55953, is engraved
in white on the front of the base below the window. A white plastic
oval tag folds out from beneath the serial number on the base
with specifications handwritten in for this instrument:
SENS. .00003 uA/MM
C.D.R.X. 70000 [ohms]
PERIOD 23.5 Sec
RESIS. 831[ohms]
CAT. NO. 2285F
There is a yellow decal on the base: STATE OF CALIFORNIA
/ HUMBOLDT COLLEGE / 30408
Research: A similar instrument (Type R) is illustrated
and described on p736 of the Cenco 1960 Catalog (J-300) and on
p 1275 of the 1950 Cenco Catalog (J150).
