Usage: To determine accurate current values, as when
calibrating an ammeter, using a potentiometer. The current is
determined via Ohm's Law by dividing the potentiometer reading
by the resistance of the shunt. The multirange shunt allows the
determination of currents from 0-7.5 amps, depending on which
binding posts are connected in series with the current source.
Description: There are two Bakelite terminals at the
upper center of the top panel labeled "Potentiometer"
with the left one also labeled "A." Eight nickel plated
brass terminals are arranged across the bottom of the panel labeled:
"COMMON/A/CURRENT TERMINAL; 7.5/.2; 3/.5; 1.5/1; .75/2;
.3/5; .15/10; .075 AMPS/20 OHMS." The panel is held to the
case with six chrome plated brass slot-head screws. The instrument
has a 6 1/2 x 12 1/2" satin Bakelite top-plate, and a polished
solid mahogany case and cover. It is 6" high to the top
of the Bakelite plate. The case has air circulation slots at
the bottom and top of the front and back panels for air circulation,
as well as 32 half inch holes in the bottom of the case. There
are four rubber feet which hold the case about a half inch above
the ground. Condition: excellent. There is a decal on the top
plate: State of California Humboldt College 30248.
Research: A related device, a "Volt Box"
is shown as item 83415 on pg. 1362 of the Central Scientific
Co. Catalog J-141 (1941). Use of a multirange shunt box is described
in the Directions brochure for the 7645 Student's Potentiometer
from Leeds and Northrup (1960) on pg. 13.
