Schwarzbeck NNBM 8124-400 Single Path Vehicle AMN (LISN)

Interference voltage measurements acc. 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 RFreference ground must be connected to both GND-terminals. The red terminal of one NNBM 8124-400 must be connected to the + line and the red terminal of the other NNBM 8124-400 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 Ohms by switching the front panel switch to “50 Ohm 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 8124-400 can be used for bulk current injection tests utilizing a current injection clamp. The maximum continuous power rating is 50 W (at the EuT-terminals). Under continuous load at 50 W the LISN housing heats up to approx. 60° C at the front panel. The operator must be aware of high temperatures. The top and bottom perforated metal plates of the NNBM 8124-400 must not be covered under any circumstances! A sufficient air-circulation must be provided at any time to avoid overheating of the LISN.

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

Transient measurements acc. ISO 7637-2
The NNBM 8124-400 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 dimensioned according to CISPR regulations, high leakage currents to ground do occur. Normally it is not possible to use a LISN on power lines connected to ground current safety switches (they disconnect power due to excessive ground current). Either a special power line outlet which is not connected to the 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.

Continuous high current operation
The NNBM 8124-400 is not equipped with cooling fans. If the unit is put on its own aluminium feet there is only a small slot as air intake. Under these circumstances the LISN can be used with a current of 250 A continuously. The maximum allowable current can be increased remarkably by propping the LISN up in a way that the air intake slot becomes larger. The perforated sheets on bottom and top must not be covered by the props. The temperature curves at the end of this data sheet have been measured without any cooling arrangements. The surface temperature at the built in air core inductor should not exceed 160 °C.

Application:

The main application of the unsymmetrical single path AMN (artificial mains network) NNBM 8124-400 is the measurement of interference voltage in vehicles, aircrafts and ships within the HF-VHF range 0.1 – 150 MHz. The NNBM 8124-400 can also be used for bulk current injection (BCI) testing or for transient measurements according to ISO 7637-2. The impedance characteristic is implemented according to CISPR 16-1-2 and CISPR 25 with (5µH + 1 Ohm) || 50 Ohm.

The continuous current rating is 250 A, for a short time more than 500 A are possible. With its high voltage and current specification this automotive LISN fits well for electric vehicle (EV), hybrid drive and on-board battery electronics testing. The EuT is connected to the wing terminals at the front panel. The mains terminals are on the backside.