R&S MDS-21
Operation of the Absorbing Clamp
User Manual 1142.8407.04 - 02
E-11
5
Operation of the Absorbing Clamp
5.1 Function
The absorbing clamp consists of a number of ferrite ring cores arranged in a row that
surround the EUT’s cable. Some of these ring cores are part of the current transformer.
The output voltage of the current transformer is proportional to the high-frequent
current in the test cable and is fed to the measuring receiver via an internal ferrite-
loaded RF cable. With power cables, the measurement result is not affected by the
magnitude of the current since the currents of the forward and return leads cancel each
other out. A coaxial filter stops the high frequent interference currents which could
circulate via the cable shielding between the absorbing clamp and the measuring
receiver.
MDS absorbing clamps consist of a two-part plastic case that can be opened. Each
part includes a set of ferrite ring core halves. In the upper part, the halves are arranged
in spring-
loaded holding devices to form a channel that surrounds the EUT’s cable.
Closing the upper part of the plastic case completes the magnetic loop around the
cable. Practical eccentric catches provide the necessary contact pressure.
The clamp has ball bearing rollers rated for the continuous use that is typical of
automatic measurements. This allows it to move until it finds the location of maximum
disturbance.
5.2 Disturbance Power Measurement Example
shows an example of the measurement setup for disturbance power
measurements in line with the CISPR 16-2-2 basic standard. The corresponding
product standard (e.g. CISPR 14-1/EN 55014-1) may contain different requirements.
Fig. 5
Measurement setup for tabletop equipment in line with CISPR 16-2-2
