Page
9
of
10
INSTRUCTION
MANUAL
FOR
LI
‐
215A
LINE
IMPEDANCE
STABILIZATION
NETWORK
(LISN)
114
OLINDA
DRIVE
●
BREA,
CALIFORNIA
92823
●
(714)
528
‐
8800
●
fax
(714)
528
‐
1992
●
com
‐
power.com
REV043013
7.0
LISN
Theory
7.1
Overview
Line
Impedance
Stabilization
Networks
used
supply
standardized
line
impedance
to
the
EUT
during
conducted
emissions
testing
which
is
independent
of
the
external
power
line
impedance.
The
standardized
impedance
enables
consistent
readings
for
RF
noise
measurements
on
the
power
line.
The
model
LI
‐
215A
consists
of
two
separate
LISN
networks
housed
in
a
single
enclosure
for
testing
EUTs
with
single
phase
power
requirements
down
to
9
kHz.
In
addition
to
providing
standardized
impedance,
the
LISN
also
acts
as
a
low
pass
filter
for
the
power
to
equipment
under
test.
The
LISN
blocks
RF
noise
from
the
power
line
from
reaching
the
equipment
under
test,
however,
the
power
to
the
equipment
passes
through
the
LISN
with
minimal
effect.
This
filter
comprises
of
two
stage
low
pass
LC
filters.
Therefore,
there
are
two
capacitors
and
two
inductors
for
the
filters.
The
two
inductors
used
in
the
LI
‐
215A
are
air
core
type
to
eliminate
the
possibility
of
saturation
and
to
provide
stability.
The
LISN
also
provides
a
low
impedance
path
for
the
RF
noise
from
the
EUT
to
the
measuring
equipment,
thereby
facilitating
the
measurement
of
the
RF
noise.
The
insertion
loss
of
the
measured
noise
may
be
significant
at
low
frequency.
Therefore,
at
frequencies
below
400
kHz,
the
insertion
loss
correction
factor
must
be
compensated
for
highest
accuracy
noise
measurement.
The
schematic
of
the
LISN
as
well
as
line
impedance
is
specified
in
the
ANSI
C63.4
as
CISPR
‐
16
‐
1
‐
2
standards.
A
typical
circuit
diagram
of
an
LISN
is
given
in
Figure
1
below.
Figure
1
–
Example
of
an
equivalent
LISN
circuit