LANGER EMV-Technik ESA1 User Manual page 20

LANGER
DE-01728 Bannewitz
mail@langer-emv.de
EMV-Technik
www.langer-emv.com
Figure 29 Evaluation of the modifications with the HFW 21
Tap the voltage directly at the GND terminal of the interface plug via a short measuring cable to the
COM port of the HFW 21. Thus the modifications that have been made directly on the interface
module can be evaluated.
3) Data streams fed into the connected cable
Assumption:
The interface driver module feeds a RF current into the signal wires of the data cable. This current
couples to the shield via the cable capacitance of signal wire - shield and flows back to the GND of
the interface module. It generates a voltage difference between the shield and GND in the area of
the shield connection which causes disturbances being emitted.
Measurement:
Carry out this measurement without changing the measurement set-up. Simply connect the
HFW 21 directly to the shield of the plugged-in data cable (Figure 30). Thus the voltage drop can
be detected as expected.
Figure 30 HFW 21 detects the voltage drop on the shield of the connected data cable
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ESA1