
28-26 Electrical Variables
and
C
C R
R R C
x
=
+
1 2
3
2
1
2
1
2
1[ ( )]
ω
(2
8
.32
)
It
c
an
a
lso
b
e
s
hown
t
hat
ω
2
1 1
1
=
R C R C
x x
(2
8
.33
)
As
in
dicated
in Eq
uation
28.33
,
th
e
Wie
n
Br
idge
ha
s
an im
portant
ap
plication
in de
termining
th
e
fr
e-
quency
in RC os
cillators
. In fr
equency
me
ters,
C
1
and C
x
are made equal, and the two capacitors are
ganged together so that the frequency at which the null occurs varies linearly with capacitances.
28.5.4.4 Schering Bridge
Figure
28.17 il
lustrates
th
e
co
nguration
of th
e
Sc
hering
Br
idge
. i
s
br
idge
is us
ed
fo
r
me
asuring
th
e
ca
pacitance,
th
e
di
ssipation
fa
ctors,
an
d
th
e
lo
ss
an
gles
. e un
known
ca
pacitance
is di
rectly
pr
opor-
tiona ...