EMC Test Club
Conducted emissions...

standard LISN to CISPR16The incoming single phase 230V 50Hz mains supply to the screened room is filtered by a 32A filter, and then supplies the equipment via the LISN (Line Impedance Stabilisation Network), whose function is to provide a standardised impedance to the EUT, and to safely connect to the spectrum analyser. The CISPR16 Standard defines the LISN characteristics, and the LISN installed in the Test Club meets this specification. The RF signal from the LISN is then passed through a transient limiter, to prevent damaging transients on the mains line (e.g. from switching the EUT on/off) from reaching the spectrum analyser, and a 9kHz to 30MHz bandpass filter to limit unwanted signals (e.g. 50Hz). Common standards for conducted emissions call for a 30MHz upper limit, although this is not always the case. The transient limiter / bandpass filter has an attenuation factor of -10dB, and a wideband amplifier can be added if required (after initial scans without it, to ascertain levels).

The signal is further filtered by a pre-selector unit, which has one of eight filter paths in the range 150kHz and 30Mhz, selected automatically by the software which is also controlling the Laplace SA1000 spectrum analyser. This greatly enhances the selectivity of the spectrum analyser, providing a high level of out of band signal rejection, and preventing compression which would otherwise give false results.

The combination of filtered, screened room and measuring equipment that incorporates a preselector will assure you of top class results for your conducted mains emission tests, with easy to use TestEngineer Software and helpful Work Instruction Procedures and templates.

The Standard selected will specify the transducer required for measurement. For mains conducted emissions, this will be a CISPR16 - compliant LISN. The screened testroom is set up according to the Standards, with 0.8m high bench, vertical ground plane 0.4m from the EUT, etc.