LANGER EMV-Technik ESA1 User Manual page 19

LANGER
DE-01728 Bannewitz
mail@langer-emv.de
EMV-Technik
www.langer-emv.com
Measurement:
Now briefly connect a COM output of the HFW 21 with the GND of the interface module
(Figure 28). The voltage difference generated in the area of the plug-and-socket connector causes
a compensating current to flow through HFW 21 and its capacitive connection to the ground plate
back to the GND of the basic unit. This compensating current is measured with the HFW 21 and
reflects the amount of the plug-and-socket connector area's share of disturbances being emitted by
the whole unit under test. The effects of modifications such as filters or changing the plug
assignment are directly measurable.
Figure 28 GND of the interface module connected to the COM output of the HFW 21
2) Electronic components (processor with memory chip) on the interface module
Assumption:
The electronic components on the interface module generate currents in the GND system of the
interface module which provoke a voltage drop between the connection points of the two plug-and-
socket connectors. This voltage difference is decoupled via the data cable and causes disturbance
emissions.
Measurement:
The basic unit is still connected to the GP 23 ground plate. The remaining share of the plug-and-
socket connector between interface module and basic unit is dramatically reduced by several
large-area GND connections between both GND surfaces (Figure 29).
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ESA1