- 17 -
LANGER
EMV-Technik
DE-01728 Bannewitz
[email protected]
www.langer-emv.com
ESA1
4.1.2 Unit under test with several cable terminals
The aim is a measurement set-up which is as simple and easily comprehensible as possible. All
cables that are not crucial for operating the unit under test are thus disconnected. A restricted
function due to missing data, for example, is generally acceptable because essential RF sources
on the module, such as the clock line and processor, are still operational in this case even if minor
changes arise due to other program sequences, for example. After having found and minimized the
main disturbance emissions causes, carry out respective control measurements and, if necessary,
connect one cable after the other (
Figure 24
and
Figure 25
).
Replacing cables that are not crucial for
operation with a link to the ground plate:
Establish a direct conductive connection
from the GND terminal of the plug-and-
socket connector to the ground plate
instead of the cable in the simplest case.
Figure 24
You can also establish a capacitive
connection from GND or Vcc, for
example, to the ground plate.
Measure the influence of (clocked and
operationally static) data lines via a direct
capacitive connection from these data
lines to the ground plate (also see 4.1.5
External data lines).
Figure 25
4.1.3 Unit under test with indispensable cables
If you cannot disconnect and simulate cables by an equivalent capacitance or conductive
connection for functional reasons, you have to put and fix the cable on the ground plate
(
Figure 26
). If the cable leaves the ground plate, use ferrites (still on the ground plate) to prevent
the cable position and length outside the defined measurement set-up from interfering with the
measurement result and prevent interference currents, which flow in from the surroundings via
these cables from being damped.
Figure 26
