
35-6 Electromagnetic Variables
e Q-meter can be used to determine C
d
, which will also allow for an accurate calculation of induc-
tance
. D
etermining
C
d
is a matter of resonating the inductor under test at more than one frequency.
To un
derstand
ho
w
th
e
tw
o-frequency
me
asurement
wi
ll
al
low
th
e
de
termination
of C
d
, assume that
an in
ductor
is re
sonated
at a fr
equency
f
1
. e relationship between the applied frequency, f
1
, and the
ca
pacitor
o
f
t
he
Q-
meter
to o
btain
r
esonance
i
s
f
L C C
1
1
1
2
=
+
π
( )
d
(3
5
.10
)
where
C
1
is the capacitance set on the Q-meter.
Re
sonating
th
e
sa
me
in
ductor
at a se
cond,
hi
gher,
fr
equency,
f
2
, requires a Q-meter capacitance
of ...