1.2.2.
Measuring impedance
Impedance can be measured in series or in parallel. In parallel
mode, impedance can be represented as reciprocal of admittance
(
Y
). The admittance can be defined as
Y
=
G
+ j
B
, where:
G
= Conductance
B
= Susceptance
Series impedance
Parallel admittance
Rp
= Parallel resistance
Xp
= Parallel reactance
Cp
= Parallel capacitance
Lp
= Parallel inductance
Y
= 1/
Z
= 1/
Rp
+ 1/j
Xp
=
G
+j
B
Ls
= Series Inductance
Xs
= Series reactance
Cs
= Series capacitance
Rs
= Series resistance
To understand the ratio of resistance and reactance, it is
important to consider two factors: quality factor (
Q
) and
dissipation factor (
D
). Usually
Q
is used when measuring
inductance and
D
is used when measuring capacitance.
D
is
defined as the reciprocal of
Q
.
Q
= 1/
D
= tan
Θ
Q
=
Xs
/
Rs
= 2
π
f
Ls
/
Rs
= ½
π
f
CsRs
Q
=
B
/
G
=
Rp
/|
Xp
| =
Rp
/2
π
f
Lp
= 2
π
f
CpRp
- 4 -