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5.5.2 ESD test set up
Ports w
hich must be tested:
Enclosure Ports include operational keys, displays, ground and earth points, metallic parts such as
connectors etc.
Coupling path:
Basically all types of coupling exist during static discharges. Practical experience shows that, for most
electronic equipment, the current is the dominant parameter.
In practice the path of the discharge current plays an important role e.g. if secondary sparks or breakdown
in the EUT occur the test is no longer reproducible.
The frequencies contained in the ESD discharge current are higher than in the EFT spike impulse. As a
consequences, reproducibility of the ESD test is more difficult than the reproducibility of the EFT test
results. The ESD test is a most complex transient test.
Test set-up:
As shown by the example in the IEC document 61000-4-2 the same test set up can be used for all different
discharge modes (contact-, air- and indirect-discharge). Under the table lays the reference ground plan and
on the horizontal coupling plane is placed on the table.
The test mode used depends on the test object.
The three different kinds of test object are:
Metallic equipment under test
EUT
Combination such as metal
case, insulated keyboard
Insulated EUT plastic, paint,
varnish
I
I I I
I
I
-<----<----<---- -----<----I I---------> --->---->---->--I
I
with contact possibility
I
with discharge
----<-----<
I
voltage test with IEC finger and
Umax
I I I
I I I
I
I
without contact possibility
I
without discharge
( breakdown)
I I I
Discharge directly contacted
with relay tip
Air discharge with IEC finger.
Holding time 5 seconds.
Indirect test with coupling plane
and relay
direct discharge air discharge indirect discharge
The ESD transient test is a single event test. The susceptibility of an EUT is strongly influenced by the
clock frequency. With the clock frequency, the information will be transmitted in the EUT or to the auxiliary
equipment within a system. The ESD pulse enters the EUT when no information is being transmitted, the
EUT has a very good immunity to EMC test, whereas the equipment will fail in operation. The existing ESD
testers on the market the discharge cannot be synchronised with the clock frequency. Therefore the
number of shots must be increased up to 100 discharges.
Safety:
ESD discharges are not dangerous for humans.
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