Usage/History: The potentiometer is used to measure
voltages by comparison to a known reference voltage. The current
instrument is composed of a series of precision resistors which
may be placed in series with a precision slide-wire resistor
to create a resistance of known value. In use the instrument
is connected to known and unknown voltage sources, and the resistors
are adjusted until the voltages are matched as indicated by a
null reading on a sensitive galvanometer. The instrument is also
set-up so that the known source may be readily calibrated against
a reference voltage source (generally a Weston standard cell).
The potentiometer made up the heart of a great number of instruments
for measuring such quantities as pH, conductivity, light intensity
etc.
Some contemporary/early descriptions of the potentiometr
and its use are provided below:
