The
Wheatstone
Bridge
consists of
two
resistive
potential
dividers
connected to
a common
voltage
source. If
one
potential
divider has
resistances
R1
and R2
in series
and the
other
potential
divider has
resistances
R3
and R4
in series,
with R1
and R3
connected to
one side of
the voltage
source and
R2
and R4
connected to
the other
side of the
voltage
source, then
at the
balance
point where
the two
resistively
divided
voltages are
equal:
R1
/ R2
= R3
/ R4
If the value
of
resistance
R4
is unknown
and the
values of
resistances
R3,
R2
and R1
at the
balance
point are
known, then:
R4
= R3R2
/ R1
