Schwarzbeck NNBM 8124-200 Single Path Vehicle AMN (LISN)

Interference voltage measurements (CISPR 25)

Mains is connected at the back side. The 1µF capacitor must be switched on to filter external disturbance and to provide best isolation values. The DuT is connected to the front panel. The disturbance voltage is coupled to the BNC connector where it can be measured with an EMI receiver. For this purpose the switch at the front panel must be switched to “Measure”. In most cases one AMN has to be used for each line (e.g. + and -). The RF-reference ground must be connected to both GND-terminals. The red terminal of one NNBM 8124-200 must be connected to the + line and the red terminal of the other NNBM 8124-200 must be connected to the – line. The LISN that is connected to the line that is being measured has to be switched to “Measure”. The other one has to be terminated with 50 Ω by switching the front panel switch to “50 Ω termination”.

The 4 mm laboratory jacks at front- and back panel and the flat aluminium feet are electrically connected to the GND-terminals.

Immunity tests with bulk current injection (BCI-tests):
The NNBM 8124-200 can be used for bulk current injection tests and disturbance voltage measurements utilizing a clamp-on ammeter. The maximum continuous power rating is 50 W (at the EuT-terminals). With a continuous power input of 50 W the LISN housing heats up to approx. 60° C at the front panel. The operator must be aware of high temperature. The top and bottom hole-plates of the NNBM 8124-200 must not be covered under any circumstances! A sufficient air-circulation must be provided at any time to avoid overheating of the LISN. A light smell of coating and insulating material may appear in the first hours of operation, take care for not inhaling the emitted gas. The smell will disappear after some hours of operation under high temperature.

During bulk current injection tests dangers may arise by high field strengths and temperatures (fire hazard!), therefore these tests must be performed by qualified personnel only! The relevant safety precautions must be considered!

Usually the switch position "50 Ω Termination" is used for BCI-tests. The power injected at the EuT-terminals is converted to heat inside the 50 Ω / 50 W resistors. Please note: If the LISN is switched to “Measurement”, the injected RF-Power will be routed from the EuT-terminals straight to the BNC-output without any attenuation. Eventually connected RF-measuring equipment may be damaged!

Transient measurements (ISO 7637-2)
Weiterhin findet die NNBM 8124-200 Anwendung zur Messung von Transienten nach ISO 7637-2. Um Transienten nicht kurzzuschließen, muss der netzseitige 1µF Kondensator hierzu abgeschaltet werden! The NNBM 8124-200 can be used to measure transients according to ISO 7637- 2. The 1µF capacitor on the mains side could short transients and must be switched off for this purpose.

Notice:

Since the circuitry is according to CISPR 16 high discharge currents do occur. It is normally not possible to use a LISN on power lines with ground current safety switches (They disconnect power due to excessive ground current). Either a special power line outlet without ground current safety switch must be installed (warning label required!), or an isolating power line transformer 1:1must be used.

In any case, ground-connect LISN before connecting to power line. Precise safety instructions must be provided to any user of the LISN.

Application:

The main application of the unsymmetrical single path AMN (artificial mains network) NNBM 8124-200 is the measurement of interference voltage in vehicles, aircrafts and ships in the HF-VHF range 0.1 – 150 MHz. The NNBM 8124-200 can also be used for bulk current injection (BCI) testing or for transient measurements according to ISO 7637-2. The impedance characteristic is realized according to CISPR 16/25 ((5 µH + 1 Ω) || 50 Ω).

The continuous current rating is 200 A, for a short time more than 280 A are possible. The EuT is connected to the wing terminals at the front panel. The mains terminals are on the backside.