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INSTRUCTION MANUAL FOR LI-1100
LINE IMPEDANCE STABILIZATION NETWORK (LISN)
19121 El Toro Road, Silverado, California 92676
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(949) 459-9600
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com-power.com
REV121014
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-1100 consists of two separate LISN networks housed in separate
enclosure for testing EUTs with single phase power requirements.
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 single stage low pass LC filter. Therefore, it has capacitor
and an inductor for the filter. The inductor used in the LI-1100 is 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
