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The TBOH01 5µH LISN is a device required to setup conducted noise measurements of DC-powered devices. It is designed to be used for EMC pre-testing in the frequency range of 150kHz to 110 MHz.
The LISN is inserted into the supply line of the DUT (Device Under Test). Conducted noise which is present at the supply terminals of the DUT can be measured at the BNC connector using a spectrum analyzer or a measurement receiver. The source (supply) terminal and the DUT terminal are decoupled by a 5µH inductor.
- Frequency range: 100kHz – 110MHz (1GHz, see figure 4 in the manual)
- DC Resistance: 35 mΩ
- Maximum current: 10A
- Maximum source voltage: 200V

300kHz...100MHz, measured impedance of the 5μH LISN

TekBox TBOH01 LISN CISPR 25 impedance

Standard Setup
Conducted noise measurements are typically conducted using a sheet metal as ground plane. The GND terminals of all involved devices are connected to the metal shield using short cables.
As the measurement will be conducted in lab, rather than in a shielded chamber, a background noise measurement should be carried out with the DUT switched off or disconnected in order to be able to differentiate between conducted noise spectrum and background electric smog.
The picture below shows a typical conducted emissions measurement setup, such as specified in CISPR-25 standard. Setup details will differ depending on the type of DUT and applicable standards. For example, if the DUT has a vehicle power return line shorter than 200 mm, one LISN is inserted into the positive supply line. If the vehicle return line of the DUT is longer than 200 mm, two LISNs are required. One for the positive supply line and one for the power return line.
Example setup for a conducted noise measurement of a DC powered device
TekBox setup Cispr 23

The screenshot above shows the result of a CISPR 25 conducted noise measurement of a DC/DC converter carried out with two TBOH01, a Rigol DSA815 and the Tekbox PC SW EMCview. With reference to the CISPR 25 limits, the measurement result shows compliance with Class 5 limits.

Example: conducted emissions, pre-compliance measurement of an automotive LED driver using two LISNs

TekBox cispr example